ENDOCARDIAL SOLUTIONS INC
S-1/A, 1998-01-09
SURGICAL & MEDICAL INSTRUMENTS & APPARATUS
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                  SUBJECT TO COMPLETION, DATED JANUARY 9, 1998
    
 
   
PROSPECTUS
    
 
   
DATED JANUARY 9, 1998
    
 
                                 750,000 SHARES
 
                                     [LOGO]
                                  COMMON STOCK
 
This Prospectus relates to an aggregate of 750,000 shares (the "Shares") of
Common Stock, par value $.01 per share (the "Common Stock"), of Endocardial
Solutions, Inc., a Delaware corporation ("ESI" or the "Company"), that may be
sold from time to time by Medtronic Asset Management, Inc., a wholly owned
subsidiary of Medtronic, Inc. (collectively "Medtronic" or the "Selling
Stockholder"). See "Selling Stockholder." The Company will not receive any
proceeds from the sale of the Shares. The Company has agreed to pay the expenses
of registration of the Shares, including certain legal and accounting fees.
 
Any or all of the Shares may be offered from time to time in transactions on the
Nasdaq National Market, in brokerage transactions at prevailing market prices or
in transactions at negotiated prices. See "Plan of Distribution."
 
   
The Common Stock is traded on the Nasdaq National Market under the symbol
"ECSI." On December 31, 1997, the closing price of the Common Stock on the
Nasdaq National Market was $10.13 per share.
    
 
SEE "RISK FACTORS" BEGINNING ON PAGE 4 FOR A DISCUSSION OF CERTAIN FACTORS THAT
SHOULD BE CONSIDERED BY PROSPECTIVE INVESTORS.
 
THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.
 
   
<TABLE>
<CAPTION>
- -------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------
                                                                                    Proceeds to
                                                   Price to         Offering          Selling
                                                   Public(1)       Commissions      Stockholder
<S>                                             <C>              <C>              <C>
- -------------------------------------------------------------------------------------------------
Per Share.....................................      $10.13             (2)            $10.13
- -------------------------------------------------------------------------------------------------
Total.........................................    $7,597,500           (2)          $7,597,500
- -------------------------------------------------------------------------------------------------
- -------------------------------------------------------------------------------------------------
</TABLE>
    
 
   
(1) The Price per share for the securities offered by the Selling Stockholder is
    based on the closing sales price quoted by the Nasdaq National Market for
    the Common Stock on December 31, 1997. The Common Stock may be offered at
    the current market price, which may vary through the period during which the
    securities may be offered, or at such other prices as may be negotiated by
    the Selling Stockholder and a purchaser at the time of sale.
    
 
(2) The securities to be sold by the Selling Stockholder may be sold through or
    to securities brokers or dealers, which sales may involve the payment of
    commissions by the Selling Stockholder. There is no agreement between the
    Company and any broker or dealer respecting such sales.
 
No person has been authorized to give any information or to make any
representations other than those contained in this Prospectus in connection with
the offer contained herein, and, if given or made, such information or
representations must not be relied upon as having been authorized by the
Company. This Prospectus does not constitute an offer to sell, or a solicitation
of an offer to buy, any securities offered hereby in any jurisdiction in which
it is not lawful or to any person to whom it is not lawful to make any such
offer or solicitation. Neither the delivery of this Prospectus nor any sale made
hereunder shall, under any circumstances, create any implication that
information herein is correct as of any time subsequent to the date hereof.
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                 (This page has been left blank intentionally.)
 
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                               PROSPECTUS SUMMARY
 
    THE FOLLOWING SUMMARY IS QUALIFIED IN ITS ENTIRETY BY AND SHOULD BE READ IN
CONJUNCTION WITH THE MORE DETAILED INFORMATION AND FINANCIAL STATEMENTS AND THE
NOTES THERETO APPEARING ELSEWHERE IN THIS PROSPECTUS. INVESTORS SHOULD CAREFULLY
CONSIDER THE INFORMATION SET FORTH UNDER THE HEADING "RISK FACTORS."
 
    Endocardial Solutions, Inc. ("ESI" or the "Company") designs, develops, and
manufactures a minimally invasive diagnostic system that diagnoses, within the
span of a few heartbeats, tachycardia, a potentially fatal abnormal heart
rhythm. The Company believes that its proprietary EnSite catheter and clinical
workstation (together, the "EnSite System") is a powerful new diagnostic tool
that will enable electrophysiologists to rapidly and comprehensively map
tachycardia and improve the selection of patient treatment options.
 
    The Company has conducted limited clinical trials of the EnSite System on
patients in the United States and the United Kingdom for ventricular tachycardia
and supraventricular (atrial) tachycardia. Although clinical data obtained to
date are insufficient (and included patients who experienced complications) to
demonstrate the safety and efficacy of the EnSite System under applicable United
States and international regulatory guidelines, the Company anticipates that
these and additional clinical trials will be used to support a pre-market
approval ("PMA") application to obtain approval to market the EnSite System for
the diagnosis of ventricular tachycardia in the United States. The process of
obtaining FDA and other required regulatory approvals is lengthy, expensive and
uncertain. See "Risk Factors--Limited Clinical Testing Experience; Safety and
Efficacy Not Yet Established" and "--Lack of Regulatory Approval."
 
    Tachycardia are caused by irregular electrical activity in the heart which
disrupts the heart's normal pumping action. Ventricular tachycardia ("VT") occur
in the lower chambers of the heart and frequently lead to serious complications,
including sudden cardiac death. Supraventricular tachycardia ("SVT"), including
atrial fibrillation and flutter, originate in the upper chambers of the heart
and often result in chest pain, fatigue and dizziness and, while generally not
life-threatening, are a leading cause of stroke in the United States.
 
    It is estimated that in the United States approximately one million people
suffer from VT and approximately three million suffer from some form of SVT. The
Company estimates that a majority of these four million VT and SVT patients
suffer from complex forms of tachycardia that have multiple points of origin in
unpredictable locations in the heart ("complex tachycardia"). To date,
electrophysiologists have generally been unable to adequately diagnose complex
tachycardia due to the limited capabilities of present technology. Currently
available single-point contact catheters require time-consuming and tedious
procedures that generally produce an insufficient amount of data to effectively
locate, diagnose and optimally treat complex tachycardia.
 
    The Company's EnSite System is designed to enable electrophysiologists to
rapidly and precisely locate the multiple, unpredictable points of origin of
complex tachycardia. The EnSite System applies proprietary mathematical
algorithms to compute more than 3,000 points of electrical activity within a
heart chamber, producing a high resolution, real-time, three-dimensional color
display of the electrical activity in the heart chamber. The "virtual
electrogram" function of the EnSite System allows electrophysiologists to
instantly view the electrical activity at any of the more than 3,000 points. The
EnSite System is also capable of tracking and displaying the location and
movements of auxiliary catheters introduced into the chamber.
 
   
    The Company is a development stage company that has incurred significant
operating losses since its inception. As of September 30, 1997, the Company had
an accumulated deficit of approximately $22.8 million. See "Risk
Factors--History of Operating Losses; Accumulated Deficit; Expectation of Future
Losses." The Company's offices are located at 1350 Energy Lane, Suite 110, St.
Paul, Minnesota 55108, and its telephone number is (612) 644-7890. The Company
was incorporated in Minnesota in 1992 and was reincorporated in Delaware in
1995.
    
 
                                       3
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                                  RISK FACTORS
 
    IN ADDITION TO THE OTHER INFORMATION CONTAINED IN THIS PROSPECTUS, THE
FOLLOWING RISK FACTORS SHOULD BE CONSIDERED CAREFULLY IN EVALUATING THE COMPANY
AND ITS BUSINESS BEFORE PURCHASING SHARES OF COMMON STOCK OFFERED BY THIS
PROSPECTUS. THIS PROSPECTUS CONTAINS, IN ADDITION TO HISTORICAL INFORMATION,
FORWARD-LOOKING STATEMENTS THAT INVOLVE RISKS AND UNCERTAINTIES. THE COMPANY'S
ACTUAL RESULTS COULD DIFFER MATERIALLY FROM THE RESULTS DISCUSSED IN THE
FORWARD-LOOKING STATEMENTS. FACTORS THAT COULD CAUSE OR CONTRIBUTE TO SUCH
DIFFERENCES INCLUDE THOSE DISCUSSED BELOW, AS WELL AS THOSE DISCUSSED ELSEWHERE
IN THIS PROSPECTUS.
 
DEPENDENCE ON SUCCESSFUL DEVELOPMENT AND COMMERCIALIZATION OF THE ENSITE SYSTEM
 
    The Company's future success is entirely dependent upon the successful
development, commercialization and market acceptance of the EnSite System, the
development of which is ongoing and the complete efficacy and safety of which
have not yet been demonstrated. The EnSite System is currently the Company's
only potential product, and the Company could be required to cease operations if
the system is not successfully commercialized. The EnSite System will require
further development, significant additional clinical trials and, ultimately,
United States and international regulatory approvals before it can be marketed
in the United States and internationally. There can be no assurance that
unforeseen problems will not occur in research and development, clinical
testing, regulatory submissions and approval, product manufacturing and
commercial scale-up, marketing or product distribution. Any such occurrence
could materially delay the commercialization of the EnSite System or prevent its
market introduction entirely. The Company will not generate any significant
revenue until such time, if ever, as the EnSite System is successfully
commercialized. There can be no assurance that the Company will ever derive
substantial revenues from the sale of the EnSite System. See "Business."
 
LIMITED CLINICAL TESTING EXPERIENCE; SAFETY AND EFFICACY NOT YET ESTABLISHED
 
   
    The Company has conducted only limited clinical trials on patients for VT
and SVT in the United States and in the United Kingdom. The Company has
experienced complications in its clinical trials, and clinical data obtained to
date are insufficient to demonstrate the safety and efficacy of the EnSite
System under applicable United States and international regulatory guidelines.
Accordingly, the Company believes it will be required to conduct extensive
clinical testing in the United States in order to support a pre-market approval
("PMA") application to the United States Food and Drug Administration ("FDA")
for marketing approval. Patients selected for clinical trials must meet
stringent guidelines to undergo testing, and there can be no assurance that
patients can be enrolled in clinical trials on a timely basis. Further, there
can be no assurance that any of the Company's products will prove to be safe and
effective in clinical trials under United States or international regulatory
guidelines or that the Company will not encounter problems in clinical testing
that will cause a delay in the commercialization of the EnSite System. Moreover,
the clinical trials may identify significant technical or other obstacles to be
overcome prior to obtaining necessary regulatory or reimbursement approvals. In
addition, the Company's development of the EnSite System for diagnosing atrial
fibrillation is in its early stages. The Company received an investigational
device exemption ("IDE") from the FDA for a multi-center clinical study of the
EnSite System in diagnosing atrial fibrillation in August 1997, but to date has
conducted only limited clinical trials on patients for atrial fibrillation. The
Company has not yet applied for regulatory approval in international markets for
the use of the EnSite System in diagnosing atrial fibrillation. Securing
regulatory approval in the United States or in international markets for use of
the EnSite System in diagnosing atrial fibrillation will require extensive
clinical trials. If the EnSite System does not prove to be safe and effective in
clinical trials, the Company's business, financial condition and results of
operations will be materially adversely affected. See "Business--Government
Regulation."
    
 
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LACK OF REGULATORY APPROVAL
 
   
    The manufacture and sale of medical devices, including the EnSite System,
are subject to extensive regulation by numerous governmental authorities in the
United States, principally the FDA and corresponding state agencies, and in
other countries. In the United States, the Company's products are regulated as
medical devices and are subject to the FDA's premarket approval requirements,
which have not been satisfied. Securing FDA approvals requires the submission of
extensive clinical data and supporting information to the FDA. Although the
EnSite System has been used in limited clinical trials in the United States on
patients suffering from VT, under an IDE approved by the FDA, the Company cannot
file with the FDA a PMA application to market the EnSite System for diagnosing
VT in the United States until more extensive clinical trials are completed. The
process of obtaining FDA and other required regulatory approvals is lengthy,
expensive and uncertain and frequently requires from one to several years from
the date of FDA filing, if premarket approval is obtained at all. In addition,
the use of the EnSite System to diagnose SVT is in the initial stages of
clinical development. Though the Company has received an IDE approval from the
FDA to pursue clinical testing of the EnSite System for atrial fibrillation in
the United States, significant additional testing will be required to support a
subsequent PMA application.
    
 
    Sales of medical devices outside of the United States are subject to
international regulatory requirements that vary from country to country. The
time required to obtain approval for sale internationally may be longer or
shorter than that required for FDA approval, and the requirements may differ.
After mid-1998, the Company will be required to obtain the certifications
necessary to enable the CE Mark to be affixed to the Company's products in order
to sell its products in member countries of the European Union. The Company has
not obtained such certifications and there can be no assurance it will be able
to do so in a timely manner. In addition, significant costs and requests for
additional information may be encountered by the Company in its efforts to
obtain regulatory approvals. Any such events could substantially delay or
preclude the Company from marketing its products internationally.
 
    Regulatory approvals, if granted, may include significant limitations on the
indicated uses for which the product may be marketed. In addition, to obtain
such approvals, the FDA and certain foreign regulatory authorities may impose
numerous other requirements with which medical device manufacturers must comply.
FDA enforcement policy strictly prohibits the marketing of approved medical
devices for unapproved uses. In addition, product approvals could be withdrawn
for failure to comply with regulatory standards or the occurrence of unforeseen
problems following the initial marketing. The Company will be required to adhere
to applicable FDA regulations regarding Good Manufacturing Practices ("GMP") and
similar regulations in other countries, which include testing, control, and
documentation requirements. Ongoing compliance with GMP and other applicable
regulatory requirements will be monitored through periodic inspections by
federal and state agencies, including the FDA, and by comparable agencies in
other countries. Failure to comply with applicable regulatory requirements,
including the marketing of products for unapproved uses, could result in, among
other things, warning letters, fines, injunctions, civil penalties, recall or
seizure of products, total or partial suspension of production, refusal of the
government to grant premarket approval for devices, withdrawal of approvals and
criminal prosecution. Changes in existing regulations or adoption of new
governmental regulations or policies could prevent or delay regulatory approval
of the Company's products. Certain material changes to medical devices also are
subject to FDA review and approval.
 
    There can be no assurance that the Company will be able to obtain PMA
approval for the EnSite System for use in diagnosing VT and SVT, the
certifications necessary for affixation of the CE Mark on the Company's products
or other necessary regulatory approvals on a timely basis or at all. Delays in
receipt of or failure to receive such approvals, the loss of previously obtained
approvals, or failure to comply with existing or future regulatory requirements
would have a material adverse effect on the Company's business, financial
condition and results of operations. See "Business--Government Regulation."
 
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UNCERTAINTY OF AVAILABILITY OF TREATMENTS EMPLOYING ENSITE SYSTEM
 
    The Company has developed its EnSite System to diagnose VT and assist
electrophysiologists in selecting among treatment options. Current treatments
for VT include drugs, implantable defibrillators, surgery and, potentially,
catheter ablation. The Company believes that the EnSite System will enable
increased use of catheter ablation for treating complex VT. Because ablation
treatment for VT is a relatively new and to date an untested treatment, the long
term effects of ablation on patients are unknown. As a result, the long term
success of ablation therapy in treating VT will not be known for several years.
To date, no medical devices for treating VT patients in the United States
through catheter ablation have been approved by the FDA. Such catheter ablation
devices require PMA approval by the FDA, and there can be no assurance that any
such device will be approved by the FDA, or that any FDA approval will be
granted in the near future. Accordingly, there can be no assurance that the
catheter ablation market will develop in the near term or ever. Moreover, even
if medical devices for catheter ablation are approved by the FDA, there can be
no assurance that the market for treating VT through catheter ablation will
develop or that the EnSite System will prove useful in diagnosing VT for
treatment by catheter ablation products approved by the FDA. The Company is not
in the process of developing a catheter for ablation treatment and is entirely
dependent upon other medical device companies for the development of such
devices. If the medical devices for treating ventricular tachycardia through
catheter ablation are not approved by the FDA or, even with such approval, if a
market for treating ventricular tachycardia by catheter ablation does not
develop, the business, financial condition and results of operations of the
Company would be materially adversely affected. See
"Business--Background--Ventricular Tachycardia."
 
UNCERTAINTY OF MARKET ACCEPTANCE; TRAINING OF PHYSICIANS REQUIRED
 
    The commercial success of the EnSite System is dependent upon the number of
diagnostic procedures performed by electrophysiologists using the system. There
can be no assurance that the Company's EnSite System will gain any significant
degree of market acceptance among electrophysiologists, patients and health care
insurers and managed care providers. Electrophysiologists will not recommend
that diagnostic procedures be performed using the Company's products until such
time, if at all, as clinical data demonstrate the efficacy of such procedures as
compared to other diagnostic procedures currently available or under
development. See "Significant Competition; Rapid Technological Change." Even if
the clinical efficacy of procedures using the EnSite System is established,
electrophysiologists and other physicians may elect not to recommend the
procedures for any number of other reasons, including inadequate levels of
reimbursement. Broad use of the EnSite System will require training of
electrophysiologists, and the time required to complete such training could
adversely affect market acceptance. Failure of the Company's products to achieve
significant market acceptance would have a material adverse effect on the
Company's business, financial condition and results of operations. See
"--Uncertainty of Third-Party Reimbursement" and "Business--The EnSite System."
 
UNCERTAINTY OF ABILITY TO DIAGNOSE AND TREAT ATRIAL FIBRILLATION
 
   
    The Company intends to apply the EnSite System to the diagnosis of atrial
tachycardia, including atrial fibrillation; however, the Company has conducted
only limited clinical studies of its technology on patients suffering from
atrial tachycardia. Although the Company has received an IDE from to the FDA for
a multi-center clinical study of the EnSite System in diagnosing atrial
fibrillation, to date the Company has conducted only limited clinical trials on
patients for atrial fibrillation, and there can be no assurance that the Company
will be able to successfully extend its technology to the mapping of atrial
fibrillation or obtain regulatory approval to test and market any products
developed using such technology to map atrial fibrillation. In addition, the
Company has made and expects to continue to make significant research and
development expenditures in extending its technology to the diagnosis of atrial
fibrillation. There can be no assurance that the Company will realize any
benefit from these expenditures.
    
 
                                       6
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    Atrial fibrillation is a complex disease and the subject of continuing
research. The therapies presently available for atrial fibrillation are in the
developmental stage with no proven effectiveness. Even if the Company is
successful in extending its technology to provide products that are capable of
diagnosing atrial fibrillation, there can be no assurance that treatments for
atrial fibrillation will exist that will require the diagnostic capabilities of
any products developed by the Company. As a result, there can be no assurance
that a commercial market will ever develop for any product developed by the
Company for the diagnosis of atrial fibrillation. The Company is not currently
engaged and has no present intention to engage in researching or developing any
medical devices for the treatment of atrial fibrillation. See "Business--
Background--Supraventricular Tachycardia."
 
UNCERTAINTY OF ABILITY TO PENETRATE COMPLEX TACHYCARDIA PATIENT POPULATION
 
    The Company's EnSite System is designed to diagnose patients suffering from
complex tachycardia. The Company estimates that a majority of the four million
patients who suffer from tachycardia have complex forms of this disease.
Although the Company believes that the patients who suffer from complex
tachycardia are potential candidates for diagnosis using the Company's EnSite
System, there can be no assurance as to the number of complex tachycardia
patients that will be diagnosed using the Company's products due to a number of
factors, including patient preferences, the health and clinical history of the
particular patient, the access of the patient to electrophysiology labs
employing the EnSite System, the availability of alternative diagnostic
procedures, the availability of treatment options and the expense of the
diagnosis using the EnSite System vis-a-vis alternative diagnostic procedures.
Failure of the Company's products to achieve significant penetration of the
population of patients suffering from complex tachycardia could have a material
adverse effect on the Company's business, financial condition and results of
operations. See also "--Uncertainty of Availability of Treatments Employing the
EnSite System," "--Uncertainty of Market Acceptance; Training of Physicians
Required" and "--Uncertainty of Ability to Diagnose and Treat Atrial
Fibrillation."
 
HISTORY OF OPERATING LOSSES; ACCUMULATED DEFICIT; EXPECTATION OF FUTURE LOSSES
 
    The Company has generated no revenue and has sustained significant operating
losses each year since its inception. The Company expects such losses to
continue at least through 1999. There can be no assurance that the Company will
ever generate substantial operating revenues or achieve profitability. The
Company's ability to generate revenues from operations and achieve profitability
is dependent upon successful development, regulatory approval, manufacturing and
commercialization of the EnSite System and the Company's successful transition
from a development stage company to a manufacturing and sales company. See
"Management's Discussion and Analysis of Financial Condition and Results of
Operations" and "Business."
 
SIGNIFICANT COMPETITION; RAPID TECHNOLOGICAL CHANGE
 
    The cardiac medical device market is highly competitive and characterized by
rapid innovation and technological change. The Company's EnSite System for the
mapping of ventricular tachycardia is a new technology that must compete with
more established mapping procedures and devices such as single-point contact
catheters that are currently widely used to map tachycardia and which are
generally less expensive and, unlike EnSite catheters, are generally reused
after resterilization. Single-point contact diagnostic catheters have been
approved by the FDA for VT mapping. In addition, certain of the Company's
competitors are developing new approaches and new products for diagnosing
ventricular tachycardia and atrial fibrillation for which regulatory approval
has not been granted, including contact mapping systems using multi-electrode
basket contact catheters and single-point mapping technologies. There can be no
assurance that any of these competitors will not receive required regulatory
approval to market their products before the Company. Certain competitors have
integrated product lines that include products for both diagnosis and ablation
treatment, which may afford opportunities for product bundling and other
 
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marketing advantages. Many of the Company's competitors have an established
presence in the field of electrophysiology and established relationships with
electrophysiology labs. Many of these competitors have substantially greater
financial and other resources than the Company, including larger research and
development staffs and more experience and capabilities in conducting research
and development activities, testing products in clinical trials, obtaining
regulatory approvals, and manufacturing, marketing and distributing products.
There can be no assurance that the Company will succeed in developing and
marketing technologies and products that are more clinically efficacious or cost
effective than the more established products or the new approaches and products
developed and marketed by its competitors. Certain of the Company's competitors
may achieve patent protection, regulatory approval or product commercialization
more quickly than the Company, which may negatively impact the Company's ability
to compete. The failure of the Company to demonstrate the efficacy and cost
effectiveness of its products as compared to those of its competitors or the
failure to develop new technologies and products before its competitors would
have a material adverse effect on business, financial condition and results of
operations. See "Business--Competition."
 
    The medical device industry is subject to rapid technological innovation
and, consequently, the life cycle of any particular product is short. There can
be no assurance that alternative diagnostic systems or other discoveries and
developments with respect to mapping tachycardia will not render the Company's
products obsolete. Furthermore, the greater financial and other resources of
many of the Company's competitors may permit such competitors to respond more
rapidly than the Company to technological advances. See "Business--Competition."
 
DEPENDENCE ON PATENTS AND PROPRIETARY TECHNOLOGY
 
    The Company's success will depend in part on its ability to obtain patent
protection for its products and processes, to preserve its trade secrets and to
operate without infringing the proprietary rights of third parties. The patent
positions of medical device companies, including the Company, are uncertain and
involve complex and evolving legal and factual questions. There can be no
assurance that any pending or future patent applications will result in issued
patents, that any current or future patents will not be challenged, invalidated
or circumvented, that the scope of any of the Company's patents will exclude
competitors or that the rights granted thereunder will provide any competitive
advantage to the Company, that any of the Company's patents will be held valid
if subsequently challenged or that others will not claim rights in or ownership
of the patents and other proprietary rights held by the Company. Furthermore,
there can be no assurance that others will not independently develop similar
technologies or duplicate any technology by the Company or that the Company's
technology will not infringe patents or other rights owned by others. Moreover,
the Company cannot be certain that it was the first to make the inventions
covered by each of its issued patents and its pending patent applications, or
that it was the first to file patent applications for such inventions. In
addition, there can be no assurance that competitors, many of which have
substantial resources and have made substantial investments in competing
technologies, will not seek to apply for and obtain patents that will prevent,
limit or interfere with the Company's ability to make, use or sell its products
either in the United States or in international markets. Further, the laws of
certain foreign countries may not protect the Company's intellectual property
rights to the same extent as do the laws of the United States.
 
    There has been substantial litigation regarding patent and other
intellectual property rights in the medical device industry and competitors may
resort to intellectual property litigation as a means of competition.
Intellectual property litigation is complex and expensive and the outcome of
such litigation is difficult to predict. There can be no assurance that the
Company will not become subject to patent infringement claims or litigation in a
court of law, or interference proceedings declared by the United States Patent
and Trademark Office to determine the priority of inventions or an opposition to
a patent grant in a foreign jurisdiction. Litigation or regulatory proceedings,
which could result in substantial cost and uncertainty to the Company, may also
be necessary to enforce patent or other intellectual property
 
                                       8
<PAGE>
rights of the Company or to determine the scope and validity of other parties'
proprietary rights. There can be no assurance that the Company will have the
financial resources to assert patent infringement suits or to defend itself from
claims of invalidity. An adverse determination in any litigation could subject
the Company to significant liabilities to third parties, or require the Company
to seek licenses from or pay royalties to third parties that may be substantial.
Furthermore, there can be no assurance that the necessary licenses would be
available to the Company on satisfactory terms, if at all. Accordingly, an
adverse determination in a judicial or administrative proceeding or failure to
obtain necessary licenses could prevent the Company from manufacturing, selling
or using its proposed products, any of which would have a material adverse
effect on the Company's business, financial condition, results of operations and
prospects.
 
    In addition to patents, the Company relies on trade secrets and proprietary
knowledge, which it seeks to protect, in part, through confidentiality
agreements with employees, consultants and other parties. In particular, the
Company relies upon such means to protect the proprietary software used in the
EnSite System. There can be no assurance that the Company's proprietary
information or confidentiality agreements will not be breached, that the Company
will have adequate remedies for any breach, or that the Company's trade secrets
will not otherwise become known to or independently developed by competitors.
See "Business--Patents and Proprietary Rights."
 
LIMITED MANUFACTURING EXPERIENCE; SCALE-UP RISK
 
    The Company has only limited experience in manufacturing the EnSite catheter
and the patient interface unit of the EnSite System's clinical workstation. The
Company currently manufactures its catheters and patient interface units in
limited quantities for laboratory and clinical testing and intends to
manufacture the EnSite catheter for commercial sale. The Company has no
experience manufacturing its products in the volumes that will be necessary for
the Company to achieve significant commercial sales, and there can be no
assurance that reliable, high-volume manufacturing capacity can be established
or maintained at commercially reasonable costs. If the Company receives FDA or
foreign approval for its products, it will need to expend significant capital
resources and develop the necessary expertise to establish large-scale
manufacturing capabilities. Manufacturers often encounter difficulties in
scaling up production of new products, including problems involving production
yields, quality control and assurance, component supply shortages, shortages of
qualified personnel, compliance with FDA and foreign regulations, and the need
for further FDA or foreign regulatory approval of new manufacturing processes.
Any inability of the Company to establish and maintain large-scale manufacturing
capabilities would have a material adverse effect on the Company's business,
financial condition and results of operations.
 
   
    The Company's manufacturing facilities will be subject to periodic
inspection by United States and foreign regulatory authorities. In order to
manufacture products for sale in the United States, the Company's operations
must undergo GMP compliance inspections conducted by the FDA. To date, the
Company's facilities and manufacturing processes have not undergone any such
inspections. The Company will also be required to comply with ISO 9001 and 9002
and CE Mark standards in order to sell its products in Europe. The Company
received ISO 9001 certification for its quality system in August 1997. Any
failure of the Company to comply with GMP or ISO 9001 and 9002 and CE Mark
standards may result in the Company being required to take corrective actions,
such as modification of its manufacturing policies and procedures. In addition,
the Company may be required to cease all or part of its operations for some
period of time until it can demonstrate that appropriate steps have been taken
to comply with GMP or ISO 9001 and 9002 and CE Mark regulations. Although the
Company has received ISO 9001 certification, there can be no assurance that the
Company will be found in compliance with GMP or ISO 9001 and 9002 and CE Mark
standards in future audits by regulatory authorities or that the Company will
not experience difficulties in the course of developing its manufacturing
capability. A failure to comply with GMP or ISO 9001 and 9002 and CE Mark
standards, or to develop its manufacturing capability in compliance with such
standards, would prohibit the Company from manufacturing and distributing its
products and therefore have a material adverse effect on the Company's business,
financial condition and results of operations.
    
 
                                       9
<PAGE>
DEPENDENCE ON SOLE OR LIMITED SOURCE SUPPLIERS
 
    The Company purchases raw materials and certain key components of its
products, including the computer workstation and certain components for its
catheter, from sole, single or limited source suppliers. For certain of these
components, there are relatively few alternative sources of supply. The Company
currently has no agreements that would assure delivery of raw materials and
components from such suppliers. Establishing additional or replacement suppliers
for any of the numerous components used in the Company's products, if required,
may not be accomplished quickly and could involve significant additional costs.
The inability of any of the Company's suppliers to provide an adequate supply of
components in a timely manner, or the inability of the Company to locate
qualified alternative suppliers for materials and components at a reasonable
cost, could adversely affect the Company's business, financial condition and
results of operations. In the event the Company had to replace a single source
supplier, such replacement would be required to meet GMP and certain other
regulatory standards. See "Business--Manufacturing."
 
NEED TO MANAGE EXPANDING OPERATIONS
 
    In order to complete clinical trials in progress, prepare additional
products for clinical trials, and develop future products, the Company believes
that it will be required to expand its operations, particularly in the areas of
research and development, manufacturing, quality assurance and sales and
marketing. As the Company expands its operations in these areas, such expansion
will likely result in new and increased responsibilities for management
personnel. To accommodate any such growth and compete effectively, the Company
will be required to implement and improve information systems, procedures, and
controls, and to expand, train, motivate and manage its work force. The
Company's future success will depend to a significant extent on the ability of
its current and future management personnel to operate effectively, both
independently and as a group. There can be no assurance that the Company's
personnel, systems, procedures and controls will be adequate to support the
Company's future operations. Any failure to implement and improve the Company's
operational, financial and management systems or to expand, train, motivate or
manage employees as required by future growth, if any, would have a material
adverse effect on the Company's business, financial condition and results of
operations. See "--Dependence on Key Personnel; Need for Additional Personnel,"
"Business--Employees" and "Management."
 
LACK OF COMMERCIAL SALES AND MARKETING EXPERIENCE
 
    The Company has no experience marketing the EnSite System and has not yet
entered into any marketing or distribution arrangements for the system or hired
sales personnel. There can be no assurance that the Company will be able to
build and maintain a suitable sales force or enter into satisfactory marketing
arrangements with third parties when commercial potential develops, if ever, or
that its sales and marketing efforts will be successful. See "Business--Sales
and Marketing."
 
RISKS RELATING TO INTERNATIONAL OPERATIONS
 
   
    The Company plans to market the EnSite System through distributors in
international markets, subject to receipt of required foreign regulatory
approvals. Sales in foreign markets are initially expected to be the Company's
only source of revenue. In September 1997 the Company signed a seven-year
distribution agreement (the "Distribution Agreement") with Medtronic to market
the EnSite System for the electrophysiology markets in Europe, Japan and the
Middle East. The initial market release is expected to include two sites in
Germany, one in France, one in Italy and one in the United Kingdom. Under the
terms of the Distribution Agreement, Medtronic has been granted exclusive
distribution rights for the Company's products in Europe, Japan and the Middle
East and has been granted certain rights for distribution in other regions
outside North America. The Company retains all distribution rights in North
America. There can be no assurance that international distributors for the
Company's products will devote adequate resources to selling its products.
    
 
                                       10
<PAGE>
    Changes in overseas economic conditions, currency exchange rates, foreign
tax laws or tariffs or other trade regulations could have a material adverse
effect on the Company's ability to market its products internationally and
therefore on its business, financial condition and results of operations. The
Company's business is also expected to subject it and its representatives,
agents and distributors to laws and regulations of the foreign jurisdictions in
which they operate or the Company's products are sold. The Company may depend on
foreign distributors and agents for compliance and adherence to foreign laws and
regulations. The regulation of medical devices in a number of such
jurisdictions, particularly in the European Union, continues to develop and
there can be no assurance that new laws or regulations will not have an adverse
effect on the Company's business, financial condition and results of operations.
In addition, the laws of certain foreign countries do not protect the Company's
intellectual property rights to the same extent as do the laws of the United
States. See "Business--Sales and Marketing."
 
DEPENDENCE ON KEY PERSONNEL; NEED FOR ADDITIONAL PERSONNEL
 
    The success of the Company is dependent in large part upon the ability of
the Company to attract and retain key management and operating personnel.
Qualified individuals are in high demand and are often subject to competing
offers. In the future, the Company will need to add additional skilled personnel
in the areas of research and development, sales, marketing and manufacturing.
There can be no assurance that the Company will be able to attract and retain
the qualified personnel needed for its business. The loss of the services of one
or more members of the Company's research, manufacturing or management group or
the inability to hire additional personnel as needed would likely have a
material adverse effect on the Company's business and prospects.
 
FUTURE CAPITAL REQUIREMENTS; NO ASSURANCE FUTURE CAPITAL WILL BE AVAILABLE
 
    The Company may require substantial funds to meet its working capital
requirements for continued research and development, testing, regulatory
approval and full-scale commercial introduction of its EnSite System. In order
to meet its funding needs, the Company may be required to raise additional funds
through public or private financings, including the sale of equity or debt. Any
additional equity financings may be dilutive to current stockholders, and debt
financing, if available, may involve restrictive covenants. Adequate funds for
the Company's operations, whether from financial markets or from other sources,
may not be available when needed on terms attractive to the Company, if at all.
Insufficient funds may require the Company to delay, scale back or eliminate
some or all of its programs designed to facilitate the commercial introduction
of the EnSite System or prevent such commercial introduction altogether. See
"Management's Discussion and Analysis of Financial Condition and Results of
Operations--Liquidity and Capital Resources."
 
UNCERTAINTY OF THIRD-PARTY REIMBURSEMENT
 
    Sales of the Company's proposed products in most markets in the United
States and internationally will be dependent on availability of adequate
reimbursement for tachycardia diagnostic procedures from third-party payors,
such as government and private insurance plans, health maintenance organizations
and preferred provider organizations. In the United States, the Company's
products, if and when approved for commercial sale, would be purchased primarily
by health care providers which will then seek to be reimbursed by various third
party payors, such as Medicare, Medicaid and other government programs and
private insurance plans, for the health care services provided to their
patients. Third-party payors reimburse health care providers for medical
treatment based on a variety of methods, including a lump sum prospective
payment system based on a diagnosis related group or per diem, a blend between
the health care provider's reported costs and a fee schedule, a payment for all
or a portion of charges deemed reasonable and customary, or a negotiated per
capita fixed payment. Third-party payors are increasingly challenging the
pricing of medical products and procedures. Even if a procedure is eligible for
reimbursement, the level of reimbursement may not be adequate. Additionally,
payors may deny reimbursement if they determine that the device used in a
treatment was unnecessary, inappropriate or not cost-effective, experimental or
used for a non-approved indication.
 
                                       11
<PAGE>
    It is anticipated that the Company's EnSite catheter will be sold at a
premium in comparison to existing single point catheters used in current
diagnostic or mapping procedures, in addition to requiring an initial capital
outlay for the companion clinical workstation. Existing single point catheters,
unlike EnSite catheters, are generally reused after sterilization. In addition
to establishing the safety and efficacy of the EnSite System, and assuming no
increase in the level of reimbursement for cardiovascular procedures expected to
utilize the Company's products, the Company will be required to economically
justify the relative increased cost of utilizing the EnSite System by
satisfactorily demonstrating the enhanced benefits of the EnSite System to
health care providers and payors in terms of such factors as enhanced patient
procedural efficiencies, reduced radiation exposure and improved patient
outcomes.
 
    The commercial success of the Company's EnSite System may also be affected
by the availability of adequate reimbursement for treatments for complex VT,
including catheter ablation. To date, catheter ablation has not been approved by
the FDA for treatment of VT and is not a commonly prescribed treatment for VT.
The Company believes that the improved mapping technology of the EnSite System
may enable catheter ablation for treating complex VT.
 
    There can be no assurance that adequate levels of reimbursement will be
available to enable the Company to achieve or maintain market acceptance of its
products or maintain price levels which exceed the Company's costs of developing
and manufacturing its products. In addition, use of the Company's products will
also depend on the adequacy of third-party reimbursement for treatments that
would be used in connection with the Company's products, such as catheter
ablation treatment. There can be no assurance that adequate levels of
reimbursement for ablation treatment will be available to support the use of the
Company's products. Without adequate support from third-party payors, the market
for the Company's products may be severely limited. Moreover, the Company is
unable to predict what additional legislation or regulation, if any, relating to
the health care industry or third-party coverage and reimbursement may be
enacted in the future, or what effect such legislation or regulation would have
on the Company. There is significant uncertainty concerning third-party
reimbursement of medical devices, and there can be no assurance that third-party
reimbursement will be available in the future for the EnSite System or that any
third-party reimbursement that is obtained will be adequate. Any failure to
obtain third party reimbursement for diagnostic procedures using the Company's
products or treatment procedures that rely on the Company's products could have
a material adverse effect on the Company's business, financial condition and
results of operations. See "Business--Third-Party Reimbursement for the
Company's Products."
 
    The Company expects that there will be continued pressure on
cost-containment throughout the United States health care system. Reforms may
include mandated basic health care benefits, controls on health care spending
through limitations on the growth of private health insurance premiums and
Medicare and Medicaid spending, greater reliance on prospective payment systems,
the creation of large insurance purchasing groups and fundamental changes to the
health care delivery system. The Company anticipates that Congress and state
legislatures will continue to review and assess alternative health care delivery
systems and payment methodologies and public debate of these issues will likely
continue in the future. Due to uncertainties regarding the ultimate features of
reform initiatives and their enactment and implementation, the Company cannot
predict which, if any, of such reform proposals will be adopted, when such
proposals may be adopted or what impact they may have on the Company. See
"Business-- Third-Party Reimbursement for the Company's Products."
 
    Reimbursement systems in international markets vary significantly by country
and by region within some countries, and reimbursement approvals must be
obtained on a country-by-country basis. Many international markets have
government managed health care systems that control reimbursement for new
devices and procedures. In most markets there are private insurance systems as
well as government managed systems. There can be no assurance that reimbursement
for the Company's products will be available in international markets under
either government or private reimbursement systems. See "Business--Third-Party
Reimbursement for the Company's Products."
 
                                       12
<PAGE>
PRODUCT LIABILITY RISK
 
    The Company faces an inherent business risk of exposure to product liability
claims in the event that an electrophysiology patient is adversely affected by
its products. The Company currently carries a product liability insurance policy
covering the Company's clinical trial operations with an aggregate limit of $5
million, although there can be no assurance that the Company's existing
insurance coverage limits are adequate to cover the Company from any liabilities
it might incur in connection with the distribution of its products. Although the
Company expects to obtain product liability insurance coverage in connection
with the commercialization of the EnSite System, there can be no assurance that
such insurance will be available on commercially reasonable terms, or at all, or
that such insurance, even if obtained, would adequately cover any product
liability claim. A product liability or other claim with respect to uninsured
liabilities or in excess of insured liabilities could have a material adverse
effect on the business and prospects of the Company.
 
POSSIBLE VOLATILITY OF PRICE
 
    The trading prices of the Company's Common Stock could be subject to wide
fluctuations in response to quarter to quarter variations in the Company's
operating results, announcements by the Company or its competitors regarding the
results of regulatory approval filings or clinical trials or testing,
developments or disputes concerning proprietary rights, technological
innovations or new commercial products, governmental regulatory action,
third-party reimbursement decisions, general conditions in the medical
technology industry, or other events or factors, many of which are beyond the
Company's control. In addition, the stock market has experienced extreme price
and volume fluctuations, which have particularly affected the market prices of
many medical technology companies and which have often been unrelated to the
operating performance of such companies.
 
SHARES ELIGIBLE FOR FUTURE SALE; REGISTRATION RIGHTS
 
   
    Sales of significant amounts of Common Stock in the public market or the
perception that such sales will occur could adversely affect the market price of
the Common Stock or the future ability of the Company to raise capital through
an offering of its equity securities. Of the 8,934,441 shares of Common Stock
currently outstanding, 3,175,410 shares (including the 750,000 shares offered
hereby) are eligible for immediate sale in the public market without restriction
unless they are held by "affiliates" of the Company within the meaning of Rule
144 of the Securities Act of 1933, as amended (the "Securities Act"). The
remaining 5,759,031 shares of Common Stock are "restricted securities" as that
term is defined in Rule 144 under the Securities Act. Approximately 4,100,551 of
the restricted shares are eligible for sale, subject to compliance with the
volume limitations and other restrictions of Rule 144, and approximately 538,126
of the restricted shares may be eligible for immediate sale without restriction
pursuant to Rule 144(k). In addition, certain stockholders, beneficially holding
an aggregate of 4,705,603 shares of Common Stock, have the right, subject to
certain conditions, to include their shares in future registration statements
relating to the Company's securities and to cause the Company to register
certain Common Stock owned by them. See "Shares Eligible for Future Sale."
    
 
NO DIVIDENDS
 
   
    The Company has never paid or declared a dividend on its capital stock and
does not anticipate doing so for the foreseeable future. See "Dividend Policy."
    
 
                                USE OF PROCEEDS
 
    The Shares will be offered and sold by the Selling Stockholder for its own
account. The Company will not receive any proceeds from the sale of the Shares
pursuant to this Prospectus. The Company has agreed to pay the expenses of
registration of the Shares.
 
                                       13
<PAGE>
                              SELLING STOCKHOLDER
 
   
    The maximum number of Shares that may be sold by the Selling Stockholder
pursuant to this Prospectus is 750,000. As of the date of this Prospectus, the
Selling Stockholder owned an aggregate of 1,726,850 shares of the Common Stock
of the Company.
    
 
    The Selling Stockholder acquired the Shares in a private placement (the
"Private Placement") that was consummated concurrently with the Company's
Initial Public Offering of Common Stock on March 24, 1997. In connection with
the Private Placement, the Company granted to the Selling Stockholder demand and
incidental registration rights to require that the Company register under the
Securities Act the Shares of Common Stock purchased by the Selling Stockholder
in the Private Placement.
 
                              PLAN OF DISTRIBUTION
 
    The sale or transfer of all or a portion of the Shares offered hereby by the
Selling Stockholder or by its pledgees, donees or other applicable transferees
or successors in interest may be effected from time to time on one or more
exchanges, on the Nasdaq National Market, in the over-the-counter market, or
otherwise at prevailing market prices at the time of such sales, at prices
related to such prevailing prices, at fixed prices (that may be changed) or at
negotiated prices. The Selling Stockholder may effect such transactions by
selling directly to purchasers in negotiated transactions, to dealers acting as
principals or through one or more brokers, in an exchange distribution in
accordance with the rules of such exchange, or any combination of these methods
of sale. In addition, Shares may be transferred in connection with call options,
short sales, loans or pledges of shares, hedging transactions or similar
transactions that may be effected by the Selling Stockholder directly or with or
through broker-dealers. As of the date of this Prospectus, the Company is not
aware of any agreement, arrangement or understanding between any broker or
dealer and the Selling Stockholder.
 
    Dealers or brokers may receive compensation in the form of discounts,
concessions or commissions from the Selling Stockholder. The Company and the
Selling Stockholder may agree to indemnify such brokers or dealers against
certain liabilities, including liabilities under the Securities Act.
 
    The Selling Stockholder is not restricted as to the price or prices at which
it may sell its Shares. Sales of such Shares at less than the market price could
adversely affect the market price of the Common Stock. Moreover, the Selling
Stockholder is not restricted as to the number of Shares which may be sold at
any one time, and it is possible that a significant number of Shares could be
sold at the same time, which could also adversely affect the market price of the
Common Stock.
 
    Pursuant to agreements with the Selling Stockholder, the Company will pay
substantially all of the expenses incident to this registration of the Shares.
Under certain registration rights agreements entered into with the Company, the
Selling Stockholder will be indemnified by the Company against certain civil
liabilities, including certain liabilities under the Securities Act.
 
    The Selling Stockholder will pay all selling commissions, transfer taxes and
related charges in connection with the offer and sale of the Shares.
 
                                       14
<PAGE>
                          PRICE RANGE OF COMMON STOCK
 
    The Company consummated its initial public offering of Common Stock on March
24, 1997 at a price of $9.00 per share. The Company's Common Stock is quoted on
the Nasdaq National Market under the symbol "ECSI." The following table sets
forth the high and low prices of the Company's Common Stock for the periods
indicated as reported on the Nasdaq National Market.
 
   
<TABLE>
<CAPTION>
PERIOD                                                                         HIGH        LOW
- ---------------------------------------------------------------------------  ---------  ---------
<S>                                                                          <C>        <C>
1997
  First quarter (commencing March 24, 1997)................................  $    9.25  $    9.00
  Second Quarter...........................................................  $   10.00  $    6.88
  Third Quarter............................................................  $   15.00  $    9.63
  Fourth Quarter...........................................................  $   14.00  $    9.50
</TABLE>
    
 
   
    On December 31, 1997, the last reported sales price for the Company's Common
Stock on the Nasdaq National Market was $10.13 per share. At December 31, 1997,
there were approximately 130 record holders of the Company's Common Stock.
    
 
                                DIVIDEND POLICY
 
    The Company has never declared or paid any cash dividends on its capital
stock since its inception. The Company currently intends to invest any earnings
in the development and expansion of its business and does not intend to pay
dividends in the foreseeable future. The payment of dividends, if any, in the
future will be at the discretion of the Board of Directors and will depend on
the Company's earnings, financial condition, capital requirements and other
relevant factors.
 
                                       15
<PAGE>
                            SELECTED FINANCIAL DATA
                    (in thousands, except per share amounts)
 
   
The following selected financial data of the Company are qualified by reference
to and should be read in conjunction with Management's Discussion and Analysis
of Financial Condition and Results of Operations and the Financial Statements
and the Notes thereto included elsewhere herein. The statement of operations
data for the years ended December 31, 1994, 1995 and 1996, and the balance sheet
data at December 31, 1995 and 1996 are derived from, and are qualified by
reference to, the audited Financial Statements included elsewhere in this
Prospectus and should be read in conjunction with those Financial Statements and
Notes thereto. The statement of operations data for the nine months ended
September 30, 1997 and 1996, and for the period from May 21, 1992 (inception) to
September 30, 1997, and the balance sheet data at September 30, 1997, are
derived from unaudited financial statements included elsewhere in this
Prospectus, and include, in the opinion of management of the Company, all
adjustments (consisting only of normal recurring adjustments) necessary for a
fair presentation of the financial position and results of operations of the
Company for such periods. The results for the nine month period ended September
30, 1997 are not necessarily indicative of the results to be expected for the
entire year ending December 31, 1997 or any future period. The statement of
operations data for the period from May 21, 1992 (inception) to December 31,
1992 and for the year ended December 31, 1993 and the balance sheet data at
December 31, 1992, 1993 and 1994 are derived from audited financial statements
not included herein.
    
 
   
<TABLE>
<CAPTION>
                          PERIOD FROM
                          MAY 21, 1992                                                         FOR THE               PERIOD FROM
                          (INCEPTION)                                                     NINE MONTHS ENDED          MAY 21, 1992
                               TO                YEAR ENDED DECEMBER 31,            ------------------------------  (INCEPTION) TO
                          DECEMBER 31,  ------------------------------------------  SEPTEMBER 30,   SEPTEMBER 30,   SEPTEMBER 30,
                              1992        1993       1994       1995       1996          1996            1997            1997
                          ------------  ---------  ---------  ---------  ---------  --------------  --------------  --------------
<S>                       <C>           <C>        <C>        <C>        <C>        <C>             <C>             <C>
STATEMENT OF OPERATIONS
  DATA:
Operating expenses:
  Research and
    development.......... $        16   $     686  $   3,352  $   3,639  $   4,425  $       3,037   $       4,405   $      16,523
  General and
    administrative.......          56         285        857      1,088      1,911          1,179           1,991           6,189
  Sales and marketing....          --          39        282        123        374            137             517           1,334
                                -----   ---------  ---------  ---------  ---------        -------         -------   --------------
Operating loss...........         (72)     (1,010)    (4,491)    (4,850)    (6,710)        (4,353)         (6,913)        (24,046)
Interest income
  (expense), net.........          --           5         83        116        229            170             782           1,216
                                -----   ---------  ---------  ---------  ---------        -------         -------   --------------
  Net loss............... $       (72)  $  (1,005) $  (4,408) $  (4,734) $  (6,481) $      (4,183)  $      (6,131)  $     (22,830)
                                -----   ---------  ---------  ---------  ---------        -------         -------   --------------
                                -----   ---------  ---------  ---------  ---------        -------         -------   --------------
Pro forma net loss per
  share (1)..............                                                $   (1.12) $       (0.74)  $       (0.78)  $       (5.60)
                                                                         ---------        -------         -------   --------------
                                                                         ---------        -------         -------   --------------
Pro forma weighted
  average shares
  outstanding (1)........                                                    5,809          5,623           7,891           4,078
                                                                         ---------        -------         -------   --------------
                                                                         ---------        -------         -------   --------------
</TABLE>
    
 
   
<TABLE>
<CAPTION>
                                                                            DECEMBER 31,
                                                       -------------------------------------------------------  SEPTEMBER 30,
                                                          1992        1993       1994       1995       1996         1997
                                                          -----     ---------  ---------  ---------  ---------  -------------
<S>                                                    <C>          <C>        <C>        <C>        <C>        <C>
BALANCE SHEET DATA:
Cash and cash equivalents............................   $       2   $   4,719  $     305  $   1,864  $   6,157    $   5,971
Working capital (deficit)............................         (35)      4,675       (195)     1,417      5,549       24,076
Total assets.........................................           2       4,934      1,013      2,595      7,200       26,911
Long-term debt and capital lease obligations, less
  current portion....................................          --          --         12        160        302          483
Deficit accumulated during the development stage.....         (72)     (1,001)    (5,409)   (10,143)   (16,623)     (22,754)
Total stockholders' equity (deficiency) (2)..........         (35)      4,884        476      1,916      6,214       25,058
</TABLE>
    
 
- ------------------------
 
   
(1)  Computed in accordance with APB 15 and SAB 83 after giving effect to the
     conversion of all series of convertible preferred stock into common stock.
    
 
(2) The Company has not declared or paid any dividend for any of the periods
    presented. See "Dividend Policy."
 
                                       16
<PAGE>
                    MANAGEMENT'S DISCUSSION AND ANALYSIS OF
                 FINANCIAL CONDITION AND RESULTS OF OPERATIONS
 
    The following discussion of the financial condition and results of
operations of the Company should be read in conjunction with the Financial
Statements and the Notes thereto included elsewhere in this Prospectus. This
Prospectus contains, in addition to historical information, forward-looking
statements that involve risks and uncertainties. The Company's actual results
could differ materially from the results discussed in the forward-looking
statements. Factors that could cause or contribute to such differences include
those discussed below, as well as those discussed elsewhere in this Prospectus.
See "Risk Factors."
 
GENERAL
 
    ESI is a development stage company incorporated on May 21, 1992, in
Minnesota and reincorporated in Delaware on January 30, 1995. ESI is engaged in
the development of the EnSite diagnostic catheter and clinical workstation for
use by electrophysiologists in diagnosing and mapping abnormal heart rhythms
known as tachycardia.
 
   
    From inception through September 30, 1997, the Company has incurred losses
totaling $22.8 million, consisting of $16.5 million in research and development
expenses, $6.2 million in general and administrative expenses and $1.3 million
in sales and marketing expenses, offset by $1.2 million in net interest income.
The Company's activities have consisted of research and product development,
initial clinical trials, fund raising and development of the manufacturing
processes and marketing strategies needed to support the commercial introduction
of the Company's products. The Company expects cumulative net losses to increase
through 1999 because of anticipated spending necessary to complete the design
and development of its products, obtain regulatory approvals, introduce its
products in international markets, and establish and maintain its U.S. sales and
marketing organization. The Company anticipates that sales in certain
international markets will precede sales in the United States.
    
 
RESULTS OF OPERATIONS FOR THE YEARS ENDED DECEMBER 31, 1994, 1995 AND 1996
 
    GENERAL.  Net losses increased to $6.5 million during 1996 from $4.7 million
during 1995 and $4.4 million during 1994.
 
    RESEARCH AND DEVELOPMENT EXPENSES.  Research and development expenses
increased to $4.4 million during 1996 from $3.6 million during 1995 and $3.4
million during 1994. The increases were due primarily to the addition of
employees in software development and applied research and associated costs, as
well as the cost of prototypes of the workstation. Research and development
expenses include engineering salaries, catheter manufacturing and consulting
expenses, clinical trials, software maintenance and depreciation.
 
    GENERAL AND ADMINISTRATIVE EXPENSES.  General and administrative expenses
increased to $1.9 million during 1996 from $1.1 million during 1995 and $857,000
during 1994. The increases were due to the establishment of a quality assurance
department in mid-1995 and increases in rent and associated expenses related to
expansion of the Company's physical facility.
 
    SALES AND MARKETING EXPENSES.  Sales and marketing expenses were $374,000
during 1996, up from $123,000 during 1995 and $282,000 during 1994. The decrease
during 1995 is primarily the result of reduced utilization of external
consultants. The increase in 1996 was due primarily to the addition of employees
and increases in associated expenses.
 
    DEFERRED COMPENSATION.  Deferred compensation amortization of $773,271 was
recorded as an expense during 1996. This expense was allocated among research
and development, general and administrative and sales and marketing, based upon
the amount of deferred compensation associated with employees in those
respective departments.
 
                                       17
<PAGE>
    OTHER INCOME.  Other income increased during 1996 to $229,000, from $116,000
during 1995 and $83,000 during 1994. The increases generally reflect increased
interest earned on increased average levels of cash and securities held by the
Company resulting from the proceeds of the sale of the Company's Preferred Stock
in 1996 and Common Stock in 1997. (See Note 5 of Notes to Financial Statements.)
 
   
RESULTS OF OPERATIONS FOR THE THREE MONTHS AND THE NINE MONTHS ENDED SEPTEMBER
  30, 1997 AND 1996
    
 
   
    GENERAL.  Net losses increased to $2,182,974 for the three months ended
September 30, 1997, from $1,421,665 for the same period in 1996. The net losses
for the nine months ended September 30, 1997 and 1996 were $6,130,807 and
$4,182,669, respectively.
    
 
   
    RESEARCH AND DEVELOPMENT EXPENSES.  Research and development expenses
increased to $1,665,674 or 61% for the three month period ended September 30,
1997, from $1,036,260 during the same period in 1996. For the nine months ended
September 30, 1997, research and development expenses were $4,404,723, an
increase of $1,367,721 or 45%, from $3,037,002 for the nine months ended
September 30, 1996. The increase in each period is attributable to increases in
clinical trial expenses, personnel costs related to hiring additional
engineering staff and amortization of deferred compensation. The Company
believes that research and development expenditures will increase in the future
as the Company expands clinical research activity and increases personnel to
support product development.
    
 
   
    GENERAL AND ADMINISTRATIVE EXPENSES.  General and administrative expenses
were $758,569 and $434,242 for the three months ended September 30, 1997 and
1996, respectively. For the nine months ended September 30, 1997 and 1996,
general and administrative expenses were $1,989,828 and $1,179,084,
respectively, an increase of $810,744 or 69%. The increase in both periods was
due to increases in personnel, regulatory activities and expenses in quality
assurance associated with attaining ISO certification. In addition, the Company
incurred expenses related to expansion of the Company's facility and
amortization of deferred compensation. Administrative costs associated with
being a publicly held company, such as costs attributable to certain insurance
policies and investor relations materials, contributed to the increase for the
three months ended September 30, 1997, from the same period in 1996.
    
 
   
    SALES AND MARKETING EXPENSES.  Sales and marketing expenses increased to
$113,509 during the three months ended September 30, 1997, from $65,525 during
the same period in 1996. Total sales and marketing expenses for the nine months
ended September 30, 1997 and 1996, were $517,134 and $136,508, respectively.
This increase is due to the establishment of a marketing department. The Company
expects continued increases in sales and marketing expenses due to expanded
marketing activity including market release in Europe, participation at medical
industry conferences and seminars and market research activities.
    
 
   
    INTEREST INCOME.  Interest income was $380,447 and $125,607 for the three
months ended September 30, 1997 and 1996, respectively. Interest income for the
nine months ended September 30, 1997 and 1996 was $845,917 and $210,607,
respectively. The increase was due to the higher cash, cash equivalents and
short-term investment balances from the Company's equity offerings completed
during the quarter ended March 31, 1997.
    
 
LIQUIDITY AND CAPITAL RESOURCES
 
    On March 24, 1997, the Company received net proceeds of approximately $18.8
million from an initial public offering of 2,250,000 shares of its Common Stock
and approximately $6.3 million from a concurrent private placement to Medtronic
of 750,000 shares of its Common Stock.
 
   
    The Company's operations since inception have been funded by net proceeds
from the sales of Common and Preferred Stock totaling approximately $47 million
through September 30, 1997. As of September 30, 1997 and December 31, 1996, the
Company had cash and cash equivalents and short-term investments of
approximately $25.1 million and $6.2 million, respectively. For the nine months
ended
    
 
                                       18
<PAGE>
   
September 30, 1997, the Company used $5.2 million for operations and $224,000
for capital expenditures. Also, the Company acquired an additional $612,000 of
capital equipment financed through capital leases.
    
 
    The Company believes that its existing cash and cash equivalents and
borrowings available under the equipment lease line of credit discussed above
will be sufficient to fund the operations of the Company through the next two
years. The Company's future liquidity and capital requirements will depend on
numerous factors, including the timing of regulatory actions regarding the
Company's products, the results of clinical trials and competition, the extent
to which the Company's EnSite System gains market acceptance and the costs and
timing of expansion of sales, marketing and manufacturing activities. However,
the Company may be required to raise additional capital. There can be no
assurance that such capital will be available on acceptable terms, or at all.
See "Risk Factors--Future Capital Requirements; No Assurance Future Capital Will
Be Available."
 
                                       19
<PAGE>
                                    BUSINESS
 
THE COMPANY
 
    Endocardial Solutions, Inc. ("ESI" or the "Company") designs, develops, and
manufactures a minimally invasive diagnostic system that diagnoses, within the
span of a few heartbeats, tachycardia, a potentially fatal abnormal heart
rhythm. The Company believes that its proprietary EnSite catheter and clinical
workstation (together, the "EnSite System") is a powerful new diagnostic tool
that will enable electrophysiologists to rapidly and comprehensively map
tachycardia and improve the selection of patient treatment options. The Company
has conducted limited clinical trials of the EnSite System in the United States
and the United Kingdom on patients for ventricular tachycardia and
supraventricular (atrial) tachycardia. The Company anticipates that these and
additional clinical trials will be used to support a pre-market approval ("PMA")
application to obtain approval to market the EnSite System for the treatment of
ventricular tachycardia in the United States.
 
BACKGROUND
 
    The heart consists of four chambers: the ventricles, the lower two chambers,
and the atria, the upper two chambers. A normal heartbeat is the result of
electrical impulses generated at the sinoatrial node, the heart's natural
pacemaker located near the top of the right atrium. These impulses form a wave
of electrical activation that travels down the atria, causing them to contract
and fill the ventricles, the heart's primary pumping chambers, with blood. After
a brief delay in the atrioventricular node, located between the chambers, the
electrical activation wave enters the ventricles and produces a coordinated
contraction of the ventricles that pumps blood throughout the body's circulatory
system. The following diagrams illustrate the four chambers of the heart and the
pathway of electrical conduction within the heart.
 
                             [ILLUSTRATION]
 
    When defects in the heart tissue interfere with the normal formation or
conduction of the heart's electrical activity, abnormal heart rhythms, known as
cardiac arrhythmias, develop. Cardiac arrhythmias have numerous causes,
including congenital defects, tissue damage due to heart attacks or
arteriosclerosis (the deposition of fatty substances in the inner layer of the
arteries) and other diseases, that accelerate, delay or redirect the
transmission of electrical activity, thereby disrupting the normal coordinated
contractions of the chambers. Arrhythmias characterized by an abnormally fast
heart rate (more than 100 beats per minute) are known as tachycardia.
 
    Tachycardia fall into two categories, ventricular tachycardia (VT) and
supraventricular tachycardia (SVT). VT are tachycardia that originate in the
ventricles. SVT originate in the atria or at the junction
 
                                       20
<PAGE>
between the atria and the ventricles. Approximately four million people in the
United States suffer from some form of tachycardia.
 
    VENTRICULAR TACHYCARDIA
 
    CHARACTERISTICS OF VENTRICULAR TACHYCARDIAS.  Ventricular tachycardia, which
afflicts approximately one million Americans, is a potentially life-threatening
condition caused either by abnormally rapid impulse formation or by slow
ventricular conduction which interferes with the heart's normal electrical
activity and causes abnormally frequent contractions of the ventricles. Rapid
ventricular contractions often result in significantly reduced cardiac output
due to inefficient blood pumping. As a result, the body receives an inadequate
supply of oxygen, which can cause dizziness, unconsciousness, cardiac arrest and
death. VT conditions tend to become more serious over time. Individuals with VT
are at risk of imminent death due to its unpredictable nature.
 
    Many VT result from heart attacks caused by coronary artery disease. When a
heart attack occurs due to a blockage in one or more coronary arteries, a
portion of the heart muscle (most often in the left ventricle) dies. As a
result, irregular borders consisting of intermixed healthy and scar tissue are
formed and VT typically originate at these sites. As the average age of the U.S.
population increases, it is expected that the number of persons who suffer heart
attacks and are at risk of VT will also increase.
 
    VT is a highly complex and transient form of cardiac arrythmia which varies
significantly from patient to patient. A small percentage of ventricular
tachycardia patients have simple forms of the disease which are focused on a
single anatomic site within the ventricle. The Company estimates, however, that
of the one million patients that suffer from VT, the majority suffer from
complex VTs that (i) have multiple sites of aberrant electrical activity, (ii)
prevent sufficient cardiac output, making them dangerous to induce in the
patient (which is required for diagnosis) and (iii) are nonsustained and,
consequently, are only detectable for several heartbeats. See "Risk
Factors--Uncertainty of Ability to Penetrate Complex Tachycardia Patient
Population."
 
    DIAGNOSING VENTRICULAR TACHYCARDIA.  Patients suspected of suffering from VT
are initially screened by a cardiologist by means of external cardiac
monitoring, typically in the form of an electrocardiogram or Holter recording,
which captures electrical activity from surface leads placed on the patient's
chest for 24 hours. When further testing is warranted, the patient is referred
to a cardiac electrophysiologist for a cardiac electrophysiology ("EP") study.
 
    An EP study evaluates the electrical integrity of the heart by stimulating
multiple intra-cardiac sites and recording the electrical response. During an EP
study a patient's clinical tachycardia is induced in a controlled setting in
order to diagnose the tachycardia and select an appropriate treatment or
combination of treatments. EP studies using currently available technology are
lengthy and tedious procedures which consist of probing the interior of the left
ventricle with single-point contact catheters, causing significant discomfort
for the patient. In order to analyze the information generated by single-point
contact catheters for the purpose of prescribing treatment, electrophysiologists
review the signals measured by these catheters as multiple rows of waveforms
displayed on a computer screen. Two or more catheters are often used to provide
more information to the electrophysiologist and thereby aid in identifying the
sites of origin of tachycardia. The electrophysiologist generally constructs a
mental image of the sites of the VT within the heart's chamber by calculating
the relative timing of electrical activation among the waveforms displayed on
the computer screen. The electrophysiologist then estimates the site or sites of
origin (which correspond to the physical positions of the catheters) through
two-dimensional fluoroscopic (x-ray) projections. As the tachycardia becomes
more complex, the electrophysiologist's reconstruction of the heart's electrical
activity and location of the sites of origin becomes more difficult.
 
    The limited number of patients suffering from simple forms of VT have been
effectively diagnosed using existing single-point contact catheter technology
with diagnostic procedures that can be time consuming, tedious and invasive.
However, single-point contact catheters have limited utility in diagnosing
 
                                       21
<PAGE>
complex ventricular tachycardia. The limited data produced in point-by-point
mapping often does not provide the electrophysiologist with sufficient
diagnostic power for a complete understanding of the ventricular tachycardia.
Moreover, when attempted, diagnosing complex ventricular tachycardia with
single-point, contact catheters can take from six to twelve hours and requires
significant use of fluoroscopy to guide the catheter, which exposes both the
patient and the medical staff to radiation.
 
    In an effort to address the diagnostic shortcomings of single-point contact
catheters, there are currently under development several "basket" contact
catheters measuring multiple points of electrical activity simultaneously. These
basket catheters will require contact with the heart's surface for measurement
of electrical activity, and the Company believes that these catheters will
suffer from many of the shortcomings of single-point contact catheters.
 
    TREATMENTS FOLLOWING DIAGNOSIS OF VENTRICULAR TACHYCARDIA.  The Company's
EnSite System is designed for the diagnosis of tachycardia. The Company does not
currently design products for the treatment of this disease. However, the
Company believes that the EnSite System will provide electrophysiologists with a
diagnostic tool to improve their ability to select among available tachycardia
treatment options.
 
    Once a patient's VT is diagnosed, the electrophysiologist chooses among the
various treatment options available. Noncurative treatments include
antiarrhythmic drugs and implantable defibrillators, both of which attempt to
ameliorate the patient's condition and reduce the risks associated with the VT
but do not eliminate the cause of the tachycardia. Historically, the only
curative treatment available for VT was open heart surgery, but it has been
rarely used due to its high morbidity and mortality. More recently, however,
catheter ablation, a potentially curative treatment currently under development,
has been used in a limited number of cases for complex VT. Often
electrophysiologists prescribe a combination of drugs, defibrillators and
ablation for the treatment of VT.
 
    The table below describes the principal treatment options for VT.
 
<TABLE>
<CAPTION>
                                                                           IMPLANTABLE
                                                   ANTIARRHYTHMIC         DEFIBRILLATION           CATHETER
                                                   DRUG TREATMENT            DEVICES               ABLATION
                                                ---------------------  --------------------  ---------------------
<S>                                             <C>                    <C>                   <C>
Result of Treatment...........................  Non-curative           Non-curative          Potentially Curative
 
Invasiveness..................................  Non-invasive           Invasive              Minimally invasive
 
Approximate Cost..............................  $16,000 initially      $55,000               $16,000 (one-time
                                                and                    (approximately        cost)
                                                $8,000 per year        five to seven year
                                                                       device life)
</TABLE>
 
    Antiarrhythmic drugs, which are prescribed to chemically suppress the
arrhythmic activity, have to date been the most common treatment of VT.
Antiarrhythmic drugs are not curative and can result in considerable side
effects limiting the effectiveness of the drugs and the ability of patients to
use them over long periods of time.
 
    Automatic implantable cardioverter defibrillators ("ICDs"), which detect and
stop a tachycardia once it has started by pacing or by applying high energy
pulses, have also become a common treatment for VT. The useful life of an ICD is
approximately five to seven years, at the end of which time the ICD is generally
replaced in another surgical procedure. Many ICD patients also receive
antiarrhythmic drug therapy in an attempt to minimize the frequency of VT
episodes.
 
    There is increasing interest in the United States and Europe in using
catheter ablation to treat VT. Catheter ablation is a minimally invasive and
potentially curative treatment in which a radio frequency current is emitted
from a catheter to selectively destroy the heart tissue responsible for the
abnormal electrical activity. The use of catheter ablation to date has been
limited due to the inability of single-point
 
                                       22
<PAGE>
contact catheters to effectively map complex VT cases. Although catheter
ablation is not yet commonly prescribed to treat VT and the devices have not yet
been approved by the FDA for marketing in the United States for treatment of VT,
it is the subject of increasing technological research and development. The
Company believes catheter ablation could become a more commonly used treatment
for VT with advances in diagnostic technology such as that being developed by
the Company.
 
    SUPRAVENTRICULAR TACHYCARDIA
 
    Approximately three million of the four million people in the United States
who suffer from tachycardia have some form of SVT. Supraventricular tachycardia
is an abnormally rapid beating of the atria which may reduce the amount of blood
pumped into the ventricles, and, consequently, from the ventricles to the rest
of the body. Although SVT can be debilitating, causing chest palpitations,
fatigue and dizziness, it is generally not life-threatening. The principal types
of SVT are Wolff-Parkinson-White syndrome (WPW), Atrioventricular Nodal
Re-entrant Tachycardia (AVNRT), and atrial fibrillation and flutter.
 
    Approximately one million people in the United States suffer from WPW or
AVNRT. The tachycardia associated with WPW and AVNRT are generally easy to
diagnose and locate due to their more simple, single-site nature and predictable
location within the atria. WPW and AVNRT have been effectively treated by
catheter ablation with available contact catheters.
 
    Approximately two million people in the United States suffer from atrial
fibrillation or atrial flutter. Atrial fibrillation is characterized by a
disorganized and chaotic conduction of electrical activation, which results in
ineffective pumping of the atria. Under these conditions, blood tends to pool
and clot, increasing the risk of stroke. The American Heart Association
estimates that approximately 15 percent of all strokes in the United States are
caused by atrial fibrillation. The incidence of atrial fibrillation is linked to
aging and thus is expected to increase as the average age of the United States
population increases. See "Risk Factors--Uncertainty of Ability to Penetrate
Complex Tachycardia Patient Population."
 
    Typically, diagnosis of atrial fibrillation is easily discerned through an
electrocardiogram recording. Beyond initial detection, electrophysiologists have
had limited success in mapping atrial fibrillation using current single-point
technology due to its highly complex and chaotic nature. The inability to
effectively map and understand the origins of atrial fibrillation has hindered
the development of treatments for the disease.
 
    Antiarrhythmic drugs and anticoagulation therapy are the most commonly
prescribed treatments for atrial fibrillation, but they are not curative and
have undesirable side effects. The only known curative treatment for atrial
fibrillation is a costly and rarely performed open heart surgical procedure
known as the surgical maze procedure. The incisions made in this surgery
electrically isolate the atria into regions that can no longer maintain
fibrillation. In addition, an atrial defibrillator is under development for
detecting and controlling atrial fibrillation with low energy shocks.
 
    Catheters have been approved for ablation treatments in the atria; however,
due to the limited understanding of atrial fibrillation, to date they have not
proven effective. Catheters are under development for potentially curative
ablation of atrial fibrillation. One type of catheter under development is
designed to create linear lesions along the interior wall of the atrium to
electrically isolate regions of the chamber in a manner similar to the surgical
maze procedure. Other emerging methods are aimed at more localized ablation
treatment based on a hypothesis that atrial fibrillation is maintained in an
electrically localized region of the chamber, requiring detailed mapping.
 
    The Company believes that the complexity of atrial fibrillation and the
search for effective and curative treatments, including catheter ablation, will
require a diagnostic mapping technology that provides much greater resolution
and diagnostic capabilities than currently available technology.
 
                                       23
<PAGE>
THE ESI SOLUTION
 
    The Company is developing its proprietary EnSite System to address the need
for more rapid, comprehensive and cost-effective diagnosis of complex forms of
VT and SVT. The high resolution, three-dimensional, color display generated by
the EnSite System is designed to provide electrophysiologists greater diagnostic
capabilities than single-point contact catheter mapping devices currently
available. The EnSite System will provide electrophysiologists with a real time,
virtual image of the electrical activity of the heart without contacting the
heart's surface. The EnSite System displays more than 3,000 points of electrical
activity using the Company's proprietary algorithms. Diagnosis will be enhanced
by the "virtual electrogram" function of the EnSite System workstation that
allows electrophysiologists to instantaneously view the electrical activity at
any of the more than 3,000 points displayed by selecting a specified point on
the workstation's three-dimensional color map of the heart with the
workstation's mouse pointer. In addition, the locator function of the EnSite
System workstation will also enhance diagnosis and treatment by providing
electrophysiologists with real-time feedback as to the precise location of
auxiliary catheters introduced into the heart.
 
    The Company believes that its EnSite System for mapping tachycardia has the
following benefits over currently available single-point contact catheters:
 
    - ENHANCED DIAGNOSTIC CAPABILITY. The diagnostic power of the EnSite System
      is designed to enable electrophysiologists to make more informed decisions
      in choosing optimal treatment for tachycardia patients. The high
      resolution, three-dimensional color map generated by the EnSite System
      should greatly enhance electrophysiologists' diagnostic capabilities
      through the system's ability to capture and display a significantly
      greater amount of electrical data than can be generated with currently
      available contact catheters.
 
    - ABILITY TO MAP COMPLEX TACHYCARDIAS. ESI believes that its technology will
      enable electrophysiologists to map complex forms of VT and SVT in the
      majority of patients who cannot be mapped effectively using currently
      available technology.
 
    - REDUCED PROCEDURAL TIME. Currently available single-point contact
      catheters can require several hours of overall procedural time to diagnose
      simple tachycardia and can require between six and twelve hours to
      diagnose complex tachycardia. The Company believes that the EnSite System
      can reduce the overall procedure time significantly, greatly increasing
      the number of patients who may be candidates for diagnosis using cardiac
      mapping technology.
 
    - REDUCED RADIATION EXPOSURE. The Company believes that the speed with which
      its technology can map the heart's electrical activity and locate
      auxiliary catheters will reduce the amount of time that patients and
      medical staff are exposed to radiation from fluoroscopy, the effects of
      which are cumulative.
 
    - REDUCED COSTS. The Company believes that the EnSite System will reduce the
      costs associated with treating complex tachycardia by significantly
      reducing the amount of time required to locate and diagnose abnormal heart
      rhythms and by enabling electrophysiologists to select potentially less
      costly treatment for patients.
 
STRATEGY
 
    The Company's strategy is to establish the EnSite System as the leading
diagnostic tool for diagnosing tachycardia in the more than 700
electrophysiology laboratories in the United States and those in Europe and
Japan. The key elements of the Company's strategy are as follows:
 
    - DEMONSTRATE SAFETY AND CLINICAL EFFICACY. The EnSite System represents a
      new technology for mapping tachycardia. In order to gain acceptance of
      this technology in electrophysiology labs, the Company must demonstrate
      the safety and effectiveness of the EnSite System through successful
      clinical trials. The Company has conducted clinical trials on VT patients
      in the United States and the United Kingdom using the EnSite System. The
      Company will file results of its studies and other product information
      with the FDA and the appropriate bodies in Europe in order to seek the
 
                                       24
<PAGE>
      required approvals for marketing in the United States and Europe. In
      addition, the Company will also seek to demonstrate the clinical efficacy
      of the EnSite System through the publication of the results of its studies
      and clinical trials and articles on its technology in medical journals.
 
    - FOCUS ON VENTRICULAR TACHYCARDIAS. The Company believes that the patient
      population that suffers from complex VT that are difficult to map using
      currently available technology presents a significant market opportunity
      for the Company's EnSite System. ESI intends to focus on the ability of
      its technology to provide improved speed, increased accuracy and
      cost-effectiveness in mapping VT. This improved mapping power should
      benefit electrophysiologists in performing diagnostic procedures and
      prescribing treatments for an expanded patient population.
 
   
    - EXTEND TECHNOLOGY TO ATRIAL FIBRILLATION AND FLUTTER. The Company believes
      that the EnSite System can be extended from mapping VT to mapping atrial
      tachycardia, including atrial fibrillation and flutter, both of which
      share similar complex characteristics, such as multiple sites of origin in
      unpredictable locations. The Company has conducted studies of its
      technology for mapping atrial tachycardia in the United Kingdom, and in
      August 1997 the Company received an IDE from the FDA for the use of the
      EnSite System in the right atrium.
    
 
    - LEVERAGE RELATIONSHIPS WITH LEADING ELECTROPHYSIOLOGISTS. The Company has
      established a Scientific Advisory Board whose members are among the
      world's leading electrophysiologists. Many of these board members have
      been highly involved in the development of the Company's technology and
      products and will be critical to successful development, testing, approval
      and marketing of the Company's technology and products. The Company
      intends to utilize its Scientific Advisory Board members to assist in
      gaining market acceptance of its products.
 
THE ENSITE SYSTEM
 
    The Company's EnSite System consists of the EnSite catheter and clinical
workstation that together form an integrated system. The EnSite System is
designed to map ventricular and atrial tachycardia.
 
    THE ENSITE CATHETER
 
    The EnSite catheter is a non-contact, single-use, multi-electrode array,
percutaneous catheter, designed for use with the EnSite clinical workstation.
The EnSite catheter's multi-electrode array senses electrical activity generated
from the endocardial wall while floating in the heart chamber. The array area of
the EnSite catheter is comprised of an inflatable polyurethane balloon within a
mechanically expandable multi-electrode array. The multi-electrode array
contains a wire braid consisting of 64 braided wires. A handle and cable
connector are located at the proximal end of the catheter to allow the physician
to position the distal end of the catheter, deploy the multi-electrode array and
make electrical connection from the array to the patient interface unit of the
EnSite System's workstation.
 
    The EnSite catheter is inserted percutaneously over a standard guidewire
into a selected chamber of the heart. When positioned, the wire braid is
mechanically expanded and the balloon residing under the wire braid in the array
area of the catheter is inflated with a radiopaque solution to form an
ellipsoidal, multi-electrode array. When deployed, the array is small enough to
permit the normal functioning of the heart. In addition to the EnSite catheter,
a standard single-point diagnostic catheter is inserted in a chamber of the
heart in order to facilitate establishing the chamber's spatial boundaries. The
multi-electrode braid array collects data used to compute more than 3,000 points
of the heart chamber's electrical activity in the span of a few heartbeats by
gathering a large amount of the electrical conduction information from the
entire chamber and transmitting this information through the wire braid back
down the catheter shaft to the EnSite System's clinical workstation.
 
    THE ENSITE CLINICAL WORKSTATION
 
    The EnSite System's clinical workstation consists of the Company's
proprietary patient interface unit and a Silicon Graphics-based workstation and
other third-party peripherals, such as a color monitor, a printer and an optical
disk drive. The patient interface unit is designed to amplify and digitize the
electrical
 
                                       25
<PAGE>
information transmitted by the EnSite catheter. The patient interface unit also
accepts information generated by other auxiliary sensors, including as many as
32 standard contact catheter electrodes, which allows the electrophysiologist to
monitor clinical events or capture additional data for simultaneous display on
the workstation. The workstation is programmed with software containing the
Company's proprietary algorithms, which process the electrical information
transmitted by the EnSite catheter and reconstruct the heart's geometric layout
and the distribution of electrical activity. The heart and the electrical
activity is displayed on the workstation as high resolution, three-dimensional
isopotential or isochronal color maps. The maps can be viewed as a snapshot in
time or as an animated playback at adjustable rates of speed. The maps can also
be viewed from any perspective in space and may be zoomed in and out to
facilitate rapid diagnosis and treatment of the tachycardia, including
identifying the optimal site or sites for ablation.
 
    The electrical activity displayed on the workstation's three-dimensional map
can also be displayed as time-waveforms, called "Virtual Electrograms," at
multiple selected sites on the endocardium. Virtual Electrograms are produced by
the Company's software contained in the workstation. The electrophysiologist can
instantaneously select any of the more than 3,000 sites and waveforms to be
displayed by pointing and clicking with the workstation's mouse pointer at the
desired location on the map of the heart. The Virtual Electrogram function
provides the equivalent of positioning a standard contact catheter at the same
site on the endocardium--but without the need for actual physical contact.
 
    The EnSite System's workstation also generates a locator signal that can be
emitted from selected electrodes on standard EP catheters introduced into the
heart along with the EnSite catheter. The locator signal provides
electrophysiologists with an interactive method for locating and positioning
auxiliary catheters. The locator function is designed to allow
electrophysiologists to diagnose and treat complex tachycardia with
significantly less use of fluoroscopy than is currently required when using
presently available single-point contact catheters. The locator signal is
detected and displayed on the workstation's three-dimensional map to provide
real-time feedback to the electrophysiologist as to the precise location of the
catheter and to assist in guiding the catheter (or catheters) to a specific site
on the endocardium.
 
    The EnSite System is designed to function as a complete, integrated
electrophysiology laboratory system to provide a wide range of accurate and
versatile diagnostic tools in one product. In addition to displaying high
resolution, graphical, three-dimensional maps, the EnSite System provides
multi-channel recording from standard EP electrode catheters and standard
waveform displays. The Company intends to develop and market periodic software
upgrades and new applications for use with the EnSite System.
 
RESEARCH AND DEVELOPMENT
 
   
    To date, the Company's primary activity has been research, development and
testing of the EnSite catheter and the clinical workstation. Virtually all of
the Company's research and development activity is performed internally by the
Company's team of 26 scientists, engineers and technicians, in consultation with
the Company's Scientific Advisory Board and outside consultants. The Company's
research and development team is divided among five groups: software
engineering, applied research, hardware engineering, clinical engineering and
catheter engineering. In addition, various members of the research and
development team support the design and development of the manufacturing
processes used in fabricating the EnSite catheter.
    
 
    Among the research and development goals the Company is now pursuing are
completing necessary clinical tests, optimizing the functionality of the EnSite
System, finalizing the design of the EnSite System in anticipation of commercial
distribution, and extending the use of the system to diagnosing atrial
tachycardia. The Company expects that its future research and development
objectives will include developing new mapping and catheter configurations and
software upgrades to enhance the capabilities and ease-of-use of the EnSite
System as well as supporting the Company's manufacturing personnel in refining
manufacturing processes, improvements and scale-up in connection with the
commercialization of the EnSite System. The Company incurred research and
development expenses of approximately $3.4 million, $3.6 million and $4.4
million for the fiscal years ended December 31, 1994, 1995 and 1996,
 
                                       26
<PAGE>
   
respectively and $4.4 million for the nine months ended September 30, 1997. The
Company anticipates that it will continue to make significant investments in
research and development.
    
 
MANUFACTURING
 
    The Company manufactures its EnSite catheters in its 3,200 square foot
clean-room facility at its headquarters in St. Paul, Minnesota. The Company also
performs final assembly and system level testing of all hardware and software
components for the EnSite System clinical workstation at this facility.
 
    The manufacturing process for the EnSite catheter involves a number of steps
and component parts. The Company assembles and tests each catheter individually
prior to sterilization and packaging, which it conducts in accordance with the
requirements of the FDA. The Company has designed its manufacturing processes to
utilize automation to the extent appropriate in order to increase production
volume and reduce costs.
 
    The manufacturing of the EnSite System clinical workstation, including the
patient interface unit, involves the assembly, integration and testing of
components purchased from third parties. The Company purchases the basic
computer workstation from Silicon Graphics, and ESI software engineers program
the workstation with its proprietary software, including advanced mathematical
algorithms.
 
    The Company purchases the raw materials and various component parts for the
EnSite System from a number of suppliers. The Company has adopted rigorous
quality control measures to ensure that the component parts it purchases meet
its specifications and standards. Certain of the components are purchased from
sole source suppliers, including the computer workstation. There are relatively
few alternative sources of supply for these components, and it may be difficult
for the Company to locate additional suppliers for these components.
 
   
    The Company is implementing a manufacturing quality program designed to meet
all domestic and international standards for manufacturing medical devices. The
Company will be required to meet the requirements of the FDA's good
manufacturing practices ("GMP") in order to distribute its products in the
United States and the requirements for ISO 9001 and 9002 and CE Mark
certification in order to distribute products in Europe. The Company received
ISO 9001 certification for its quality system in August 1997. As part of meeting
such requirements, the Company's facilities and manufacturing processes will be
subject to inspection and audit. If the Company fails to satisfy the GMP
requirements or obtain ISO 9001 and 9002 and CE Mark certification, it may be
required to alter its manufacturing processes. Moreover, any such failure could
have a material adverse effect on the Company's ability to market its products,
which could adversely affect its business and results of operations. The
Company's suppliers will be required to satisfy GMP standards.
    
 
SALES AND MARKETING
 
   
    The Company intends to employ a direct sales force in the United States and
to use distributors for international markets. In September 1997 the Company
signed a seven-year distribution agreement (the "Distribution Agreement") with
Medtronic to market the EnSite System for the electrophysiology markets in
Europe, Japan and the Middle East. The initial market release is expected to
include two sites in Germany, one in France, one in Italy and one in the United
Kingdom. Under the terms of the Distribution Agreement, Medtronic has been
granted exclusive distribution rights for the Company's products in Europe,
Japan and the Middle East and has been granted certain rights for distribution
in other regions outside North America. The Company retains all distribution
rights in North America. See "Certain Transactions."
    
 
    The Company intends to direct its sales and marketing efforts at prominent
domestic and international electrophysiology laboratories that perform the
majority of electrophysiology procedures. The Company believes that prominent
electrophysiology labs are generally more likely to keep abreast of and utilize
new technologies such as the EnSite System for diagnosing and treating
tachycardia. After the Company establishes a presence in major medical centers
housing such electrophysiology labs, it then intends to broaden its sales and
marketing efforts to include the growing number of smaller, community-
 
                                       27
<PAGE>
based electrophysiology labs. As part of its strategy to gain the awareness of
and acceptance by electrophysiology laboratories, the Company has focused on and
intends to continue to focus on developing peer reviewed journal articles
authored by leading experts in electrophysiology, sponsoring publication of
papers based on research covering the performance and benefits of the EnSite
System and conducting informational seminars. In addition, as part of its
marketing program the Company expects to hold technical seminars and training
sessions to educate physicians and its direct sales force and distributors in
the use of the Company's products.
 
   
    The Company believes that it will receive approval to sell its products in
international markets before it gains approval in the United States. See
"--Government Regulation" below. The Company plans to commence selling the
EnSite System in Europe promptly following obtaining the approval of the
European authorities to distribute its products within the countries comprising
the European Union, which the Company currently anticipates should occur
sometime during the second quarter of 1998. There can be no assurance, however,
that the Company will obtain such approval at such time, if at all.
    
 
PATENTS AND PROPRIETARY RIGHTS
 
    The Company's success will depend in part on its ability to obtain patent
protection for its products and processes, to preserve its trade secrets and to
operate without infringing or violating the proprietary rights of third parties.
The Company actively pursues patent protection in the United States and foreign
jurisdictions for each of the areas of invention embodied in the EnSite System,
and will actively pursue patent protection for proprietary aspects of its
technology in the future. As of the date of this Prospectus, the Company has two
U.S. patent applications pending by which it is seeking to obtain protection for
certain enhancements currently embodied in the EnSite System, relating to the
catheter, catheter localization techniques and user interface elements. The
Company also has three issued U.S. patents which relate to the technology
underlying the EnSite System and development-stage versions of the system. One
of these patents covers the catheter of the EnSite System and its
development-stage versions. The remaining two patents are directed to
measurement methodologies used in the development-stage versions of the EnSite
System. The Company has also filed and has pending several foreign patent
applications directed to various aspects of the technology underlying the EnSite
System.
 
    The Company, like other firms that engage in the development and marketing
of medical devices, must address issues and risks relating to patents and trade
secrets. The coverage sought in a patent application can be denied or
significantly reduced before or after the patent is issued. Consequently there
can be no assurance that any of the Company's pending or future U.S. or foreign
patent applications will result in issued patents, that the scope of any patent
protection will exclude competitors or provide competitive advantages to the
Company, that any of the Company's current or future U.S. or foreign patents
will not be challenged, circumvented by competitors or others or that such
patents will be found to be valid or sufficiently broad to protect the Company's
technology. Since patent applications are secret until patents are issued in the
United States or corresponding applications are published in other countries,
and since publication of discoveries in the scientific or patent literature
often lags behind actual discoveries, the Company cannot be certain that it was
the first to make the inventions covered by each of its pending patent
applications, or that it was the first to file patent applications for such
inventions. In addition, there can be no assurance that competitors, many of
which have substantial resources and have made substantial investments in
competing technologies, will not seek to apply for and obtain patents that will
prevent, limit or interfere with the Company's ability to make, use or sell its
products either in the United States or in international markets. Further, the
laws of certain foreign countries may not protect the Company's intellectual
property rights to the same extent as do the laws of the United States.
 
                                       28
<PAGE>
    In addition to patents, the Company relies on trade secrets and proprietary
knowledge, which it seeks to protect, in part, through appropriate
confidentiality and proprietary information agreements. In particular, the
Company relies upon such means to protect the proprietary software used in the
EnSite System. The confidentiality and proprietary information agreements
generally provide that all confidential information developed or made known to
individuals by the Company during the course of the relationship with the
Company is to be kept confidential and not disclosed to third parties, except in
specific circumstances. The agreements also generally provide that all
inventions conceived by the individual in the course of rendering services to
the Company shall be the exclusive property of the Company. There can be no
assurance that proprietary information or confidentiality agreements with
employees, consultants and others will not be breached, that the Company will
have adequate remedies for any breach, or that the Company's trade secrets will
not otherwise become known to or independently developed by competitors.
 
    There has been substantial litigation regarding patent and other
intellectual property rights in the medical device industry and companies in the
medical device industry have employed intellectual property litigation to gain a
competitive advantage. There can be no assurance that the Company will not
become subject to patent infringement claims or litigation in a court of law, or
interference proceedings declared by the United States Patent and Trademark
Office (USPTO) to determine the priority of inventions or an opposition to a
patent grant in a foreign jurisdiction. The defense and prosecution of
intellectual property suits, USPTO interference or opposition proceedings and
related legal and administrative proceedings are both costly and time-consuming
and could result in substantial uncertainty to the Company. Litigation or
regulatory proceedings, which could result in substantial cost and uncertainty
to the Company, may also be necessary to enforce patent or other intellectual
property rights of the Company or to determine the scope and validity of other
parties' proprietary rights. Any litigation, opposition or interference
proceedings will result in substantial expense to the Company and significant
diversion of effort by the Company's technical and management personnel. There
can be no assurance that the Company will have the financial resources to defend
its patents from infringement or claims of invalidity. The Company is not
currently a party to any patent or other litigation. An adverse determination in
any litigation could subject the Company to significant liabilities to third
parties, require the Company to seek licenses from or pay royalties to third
parties or prevent the Company from manufacturing, selling or using its proposed
products, any of which could have a material adverse effect on the Company's
business and prospects. See "Risk Factors-- Dependence on Patents and
Proprietary Technology."
 
COMPETITION
 
    The Company believes that its competitive success will depend primarily upon
its ability to demonstrate the clinical efficacy of the EnSite System;
effectively create market awareness and acceptance of the system while
maintaining its proprietary nature; and manufacture and deliver the system on a
timely basis. The tachycardia diagnostic mapping field of the medical device
industry has attracted a high level of interest both from companies with an
established presence in the field of electrophysiology and from more recently
formed companies. The Company's competitors include companies that offer
standard, single-point contact diagnostic catheters, and companies that are
developing multi-point, basket contact catheters for diagnosing tachycardia that
use multiple electrodes to provide more data points for the measurement of the
heart's electrical activity. Basket contact catheters have not to date received
regulatory approval for diagnosing tachycardia. The Company believes that these
basket contact catheters under development can currently measure multiple points
of electrical activity in the heart. The Company is also aware of other medical
device companies that are developing alternatives to single-point contact
catheter mapping technology.
 
    The Company believes that participants in the market for mapping tachycardia
compete on the basis of clinical effectiveness, ease of use, cost and on the
basis of acceptance by health care professionals. Competition is also affected
by the length of time required for products to be developed and receive
regulatory approval. The medical device industry is characterized by rapid and
significant technological
 
                                       29
<PAGE>
change. As a result, the Company's success will depend in part on its ability to
respond quickly to medical and technological changes through the development and
introduction of new products.
 
    Many of the Company's competitors and potential competitors have
substantially greater capital resources, research and development staffs and
facilities than the Company. In addition, most of the Company's competitors and
potential competitors have substantially greater experience than the Company in
researching and developing new products, testing products in clinical trials,
obtaining regulatory approvals and manufacturing and marketing medical devices.
There can be no assurance that the Company will succeed in developing and
marketing technologies and products that are clinically more efficacious and
cost-effective than the more established diagnostic products or the new
approaches and products developed and marketed by its competitors. Moreover,
there can be no assurance that the Company will succeed in developing new
technologies and products that are available prior to its competitors' products.
The failure by the Company to demonstrate the efficacy and cost-effective
advantages of its products over those of its competitors could have a material
adverse effect on the Company's business and results of operations. See "Risk
Factors--Significant Competition; Rapid Technological Change."
 
THIRD-PARTY REIMBURSEMENT FOR THE COMPANY'S PRODUCTS
 
    In the United States, health care providers, including hospitals and
physicians, that purchase medical products for treatment of their patients
generally rely on third-party payors, principally federal Medicare, state
Medicaid and private health insurance plans, to reimburse all or a part of the
costs and fees associated with the procedures performed using these products.
The Company's success will be dependent upon, among other things, the ability of
health care providers to obtain satisfactory reimbursement from third-party
payors for medical procedures in which the Company's products are used. If FDA
approval is received, third-party reimbursement would depend upon decisions by
the Health Care Financing Administration for Medicare, as well as by individual
health maintenance organizations and private insurers and other payors.
Third-party payors determine whether to reimburse for a particular procedure
and, if so, will reimburse health care providers for medical treatment based on
a variety of methods, including a lump sum prospective payment system based on a
diagnosis related group or per diem, a blend between the health care provider's
reported costs and a fee schedule, a payment for all or a portion of charges
deemed reasonable and customary, or a negotiated per capita fixed payment. Third
party payors are increasingly challenging the pricing of medical products and
procedures. Even if a procedure is eligible for reimbursement, the level of
reimbursement may not be adequate. Additionally, payors may deny reimbursement
if they determine that the device used in the treatment was unnecessary,
inappropriate or not cost-effective, experimental or used for a non-approved
indication.
 
    It is anticipated that the Company's EnSite catheter will be sold at a
premium in comparison to existing single point catheters used in current
diagnostic or mapping procedures, in addition to requiring an initial capital
outlay for the companion clinical workstation. Existing single point catheters,
unlike the EnSite catheter, are generally reused after sterilization. In
addition to establishing the safety and efficacy of the EnSite System, and
assuming no increase in the level of reimbursement for cardiovascular procedures
expected to utilize the Company's products, the Company will be required to
economically justify the relative increased cost of utilizing the EnSite System
by satisfactorily demonstrating the enhanced benefits of the EnSite System to
health care providers and payors in terms of such factors as enhanced patient
procedural efficiencies, reduced radiation exposure and improved patient
outcomes.
 
    Medicare coverage is generally available for items and related services
involving devices that have been classified by the FDA as
"non-experimental/investigational" (Category B) devices and that are furnished
in accordance with the FDA-approved IDE governing clinical trials. Based on the
Company's IDE approval from the FDA for the EnSite System, the system has been
classified as a Category B device. Even with items or services involving
Category B devices, however, Medicare coverage may be denied if any other
coverage requirements are not met, for example, if the treatment is not
medically necessary for the specific patient. There can be no assurance that the
Company's systems will be covered when they are
 
                                       30
<PAGE>
used in clinical trials and, if covered, whether the payment amounts for their
use will be considered to be adequate by health care providers. If the devices
are not covered or the payments are considered to be inadequate, the Company may
need to bear additional costs to sponsor such trials, and such costs could have
a material adverse effect on the Company's business, financial condition and
results of operation.
 
    Capital costs for medical equipment purchased by hospitals are currently
reimbursed under Medicare separately from medical procedure payments. Recent
federal Medicare legislation has called for these capital costs to be reimbursed
on a prospective payment system. During a transition period due to end in 2000,
each hospital's capital expenditures will be based in part on its own historical
capital costs and in part on the prospective payment system. There can be no
assurance that the movement to a prospective payment system will not cause
hospitals to reduce their expenditure payments for equipment such as the EnSite
clinical workstation.
 
    Reimbursement systems in international markets vary significantly by country
and by region within some countries, and reimbursement approvals must be
obtained on a country-by-country basis. Many international markets have
government managed health care systems that control reimbursement for new
products and procedures. In most markets, there are private insurance systems as
well as government managed systems. Market acceptance of the Company's products
will depend on the availability and level of reimbursement in international
markets targeted by the Company. There can be no assurance that the Company will
obtain reimbursement in any country within a particular time, for a particular
time, for a particular amount, or at all.
 
    Regardless of the type of reimbursement system, the Company believes that
physician advocacy of the Company's products will be required to obtain
reimbursement. The Company believes that less invasive procedures generally
provide less costly overall therapies as compared to conventional drug, surgery
and other treatments. The Company anticipates that hospital administrators and
physicians would justify the use of the Company's products by the attendant cost
savings and clinical benefits that the Company believes would be derived from
the use of its products. However, there can be no assurance that this will be
the case. Accordingly, reimbursement for the Company's products may not be
available in the United States or in international markets under either
government or private reimbursement systems, and health care providers may not
advocate reimbursement for procedures using the Company's products. Failure by
hospitals and other users of the Company's products to obtain reimbursement from
third-party payors, or changes in government and private third-party payors'
policies toward reimbursement for procedures employing the Company's products,
would have a material adverse effect on the Company's business, financial
condition and results of operations. Moreover, the Company is unable to predict
what additional legislation or regulation, if any, relating to the health care
industry or third-party coverage and reimbursement may be enacted in the future,
or what effect such legislation or regulation would have on the Company.
 
    Political, economic and regulatory influences are subjecting the health care
industry in the United States to increased scrutiny. The Company anticipates
that Congress, state legislatures and the private sector will continue to review
and assess alternative health care delivery and payment systems. Potential
approaches that have been considered include mandated basic health care
benefits, controls on health care spending through limitations on the growth of
private health insurance premiums and Medicare and Medicaid spending, greater
reliance on prospective payment systems, the creation of large insurance
purchasing groups, price controls and other fundamental changes to the health
care delivery system. Legislative debate is expected to continue in the future,
and market forces are expected to demand reduced costs. In this regard, a
federal advisory panel recently recommended to Congress that the Medicare
reimbursement rate to hospitals remain unchanged in 1998. The Company cannot
predict what impact the adoption of any federal or state health care reform
measures, future private sector reform or market forces may have on its
business. See "Risk Factors--Uncertainty of Third-Party Reimbursement."
 
                                       31
<PAGE>
GOVERNMENT REGULATION
 
    UNITED STATES
 
    The Company's EnSite System is regulated in the United States as a medical
device by the FDA under the Federal Food, Drug, and Cosmetic Act ("FDC Act") and
requires premarket approval by the FDA prior to commercialization. In addition,
certain material changes or modifications to medical devices also are subject to
FDA review and approval. Pursuant to the FDC Act, the FDA regulates the
research, testing, manufacture, safety, labeling, storage, record keeping,
advertising, distribution and production of medical devices in the United
States. Noncompliance with applicable requirements can result in warning
letters, fines, injunctions, civil penalties, recall or seizure of products,
total or partial suspension of production, failure of the government to grant
premarket approval for devices, and criminal prosecution. Medical devices are
classified into one of three classes, Class I, II or III, on the basis of the
controls deemed by the FDA to be necessary to reasonably ensure their safety and
effectiveness. Class I devices are subject to general controls (E.G., labeling,
premarket notification and adherence to GMPs). Class II devices are subject to
general controls and to special controls (E.G., performance standards,
postmarket surveillance, patient registries, and FDA guidelines). Generally,
Class III devices are those which must receive premarket approval by the FDA to
ensure their safety and effectiveness (E.G., life-sustaining, life-supporting
and implantable devices, or new devices which have not been found substantially
equivalent to legally marketed devices), and require clinical testing to ensure
safety and effectiveness and FDA approval prior to marketing and distribution.
The FDA also has the authority to require clinical testing of Class I and Class
II devices. A PMA application must be filed if the proposed device is not
substantially equivalent to a legally marketed predicate device or if it is a
Class II device for which the FDA has called for such applications.
 
    If human clinical trials of a device are required and if the device presents
a "significant risk," the manufacturer or the distributor of the device is
required to file an IDE application prior to commencing human clinical trials.
The IDE application must be supported by data, typically including the results
of animal and, possibly, mechanical testing. If the IDE application is approved
by the FDA, human clinical trials may begin at a specific number of
investigational sites with a maximum number of patients, as approved by the FDA.
Sponsors of clinical trials are permitted to sell those devices distributed in
the course of the study provided such costs do not exceed recovery of the costs
of manufacture, research, development and handling. The clinical trials must be
conducted under the auspices of an independent institutional review board
("IRB") established pursuant to FDA regulations.
 
   
    The Company conducted clinical trials of its EnSite Systems on patients with
ventricular tachycardia in the United Kingdom in late 1995, 1996 and 1997 under
an authorization of the Medical Devices Agency ("the MDA") of the British
government. The Company submitted its IDE application to the FDA in May 1996
based on the results of the initial four patient trial plus extensive
pre-clinical testing. Based on consultation with the FDA, and to further support
its IDE submission, the Company conducted nine additional ventricular patient
trials and submitted this data in November 1996 in an amendment to the IDE
application. In December 1996, the FDA granted the Company an IDE to conduct in
the United States a limited clinical trial of the EnSite System for left
ventricular tachycardia mapping in five patients at one institution. The Company
conducted in early 1997 a limited five patient clinical study authorized under
the IDE. Based on the results of those trials, the FDA approved testing of the
EnSite System on an additional ten patients. The Company had completed 13 of the
15 clinical trials in June 1997 when the FDA authorized full-scale testing of
the EnSite System in 71 patients at up to five institutions in the United
States. The Company anticipates that these clinical trials will be used to
support a PMA application to obtain approval to market the EnSite System in the
United States.
    
 
   
    The Company conducted an initial study of its technology for mapping atrial
tachycardia in seven patients in the United Kingdom during the second half of
1996. The Company submitted an IDE application to the FDA in June 1997 for use
of the EnSite System in the right atrium, and received an
    
 
                                       32
<PAGE>
   
IDE approval in August 1997. The Company believes that significant testing of
the EnSite System for SVTs will be required to support a PMA application.
    
 
    A PMA application must be supported by extensive data, including preclinical
and clinical trial data, as well as extensive literature to prove the safety and
effectiveness of the device. Following receipt of a PMA application, if the FDA
determines that the application is sufficiently complete to permit a substantive
review the FDA will "file" the application. Under the FDC Act, the FDA has 180
days to review a PMA application, although the review of such an application
more often occurs over a protracted time period, and generally takes
approximately two years or more from the date of filing to complete.
 
    The PMA application approval process can be expensive, uncertain and
lengthy. A number of devices for which premarket approval has been sought have
never been approved for marketing. The review time is often significantly
extended by the FDA, which may require more information or clarification of
information already provided in the filing. During the review period, an
advisory committee likely will be convened to review and evaluate the
application and provide recommendations to the FDA as to whether the device
should be approved. In addition, the FDA will inspect the manufacturing facility
to ensure compliance with the FDA's GMP requirements prior to approval of an
application. If granted, the approval of the PMA application may include
significant limitations on the indicated uses for which a product may be
marketed.
 
    The Company plans to file a PMA application with the FDA for approval to
sell the EnSite System commercially in the United States when the clinical
studies are completed. There can be no assurance that the Company will be able
to obtain necessary PMA application approvals to market the EnSite System, or
any other products, on a timely basis, if at all, and delays in receipt or
failure to receive such approvals the loss of previously received approvals, or
failure to comply with existing or future regulatory requirements could have a
material adverse effect on the Company's business, financial condition and
results of operations.
 
    The Company is also required to register as a medical device manufacturer
with the FDA and state agencies, and to list its products with the FDA. As such,
the Company will be inspected by both the FDA for compliance with the FDA's GMP
and other applicable regulations. These regulations require that the Company
manufacture its products and maintain its documents in a prescribed manner with
respect to manufacturing, testing and control activities. Further, the Company
is required to comply with various FDA requirements for design, safety,
advertising and labeling. The Company has not yet undergone an FDA GMP
inspection.
 
    The Company is required to provide information to the FDA on death or
serious injuries alleged to have been associated with the use of its medical
devices, as well as product malfunctions that would likely cause or contribute
to death or serious injury if the malfunction were to recur. In addition, the
FDA prohibits an approved device from being marketed for unapproved
applications. If the FDA believes that a company is not in compliance with the
law, it can institute proceedings to detain or seize products, issue a recall,
enjoin future violations and assess civil and criminal penalties against the
company, its officers and its employees. Failure to comply with the regulatory
requirements could have a material adverse effect on the Company's business,
financial condition and results of operations.
 
    The advertising of most FDA-regulated products is subject to both FDA and
Federal Trade Commission jurisdiction. The Company also is subject to regulation
by the Occupational Safety and Health Administration and by other governmental
entities.
 
    Regulations regarding the manufacture and sale of the Company's products are
subject to change. The Company cannot predict what impact, if any, such changes
might have on its business, financial condition or results of operations.
 
                                       33
<PAGE>
    INTERNATIONAL
 
    International sales of the Company's products are subject to the regulatory
agency product registration requirements of each country. The regulatory review
process varies from country to country. There can be no assurance that such
approvals will be obtained on a timely basis or at all.
 
   
    The Company received ISO 9001 certification in August 1997, and is in the
process of implementing policies and procedures which are intended to allow the
Company to receive ISO 9002 qualification of its processes. The ISO 9000 series
of standards for quality operations have been developed to ensure that companies
know the standards of quality to which they must adhere to receive
certification. The European Union has promulgated rules which require that
medical products receive by mid-1998 the right to affix the CE Mark, an
international symbol of adherence to quality assurance standards and compliance
with applicable European medical device directives. ISO 9000 certification is
one of the CE Mark certification requirements. Failure to receive the right to
affix the CE Mark will prohibit the Company from selling its products in member
countries of the European Union. There can be no assurance that the Company will
be successful in meeting certification requirements.
    
 
PRODUCT LIABILITY AND INSURANCE
 
    The development, manufacture and sale of medical products entail significant
risk of product liability claims and product failure claims. The Company has
conducted only limited clinical trials and does not yet have, and will not have
for a number of years, sufficient clinical data to allow the Company to measure
the risk of such claims with respect to its products. The Company faces an
inherent business risk of financial exposure to product liability claims in the
event that the use of its products results in personal injury or death. The
Company also faces the possibility that defects in the design or manufacture of
the Company's products might necessitate a product recall. There can be no
assurance that the Company will not experience losses due to product liability
claims or recalls in the future. The Company currently maintains product
liability insurance with coverage limits of $5 million per occurrence and $5
million annually in the aggregate and there can be no assurance that the
coverage limits of the Company's insurance policies will be adequate. In
addition, the Company will require increased product liability coverage if any
potential products are successfully commercialized. Such insurance is expensive,
difficult to obtain and may not be available in the future on acceptable terms,
or at all. Any claims against the Company, regardless of their merit or eventual
outcome, could have a material adverse effect upon the Company's business,
financial condition and results of operations.
 
EMPLOYEES
 
   
    The Company had a total of 61 full-time employees as of November 30, 1997.
Of this number, 26 persons were engaged in research and development or clinical
activities, 8 were involved in regulatory and quality assurance, 16 were
involved with manufacturing and 11 were involved with administration, sales and
marketing and support functions. No employee of the Company is covered by a
collective bargaining agreement. In addition to its full-time workforce, the
Company has consulting or other contractual relationships with four other
individuals. The Company expects to add such new employees as are necessary to
expand its manufacturing capacity for future commercial production.
    
 
FACILITIES
 
   
    The Company leases approximately 17,500 square feet in St. Paul, Minnesota.
The facility is leased through March 1999. The Company believes that this
facility will be adequate to meet its needs through the full commercial
introduction of its planned products.
    
 
LEGAL PROCEEDINGS
 
    The Company is not currently a party to any legal proceedings.
 
                                       34
<PAGE>
                                   MANAGEMENT
 
EXECUTIVE OFFICERS AND DIRECTORS
 
    The names, ages and positions of the executive officers, key management
personnel and directors of the Company as of the date hereof are listed below.
 
   
<TABLE>
<CAPTION>
NAME                                      AGE  POSITION
- ----------------------------------------  ---  ----------------------------------------------------
<S>                                       <C>  <C>
James W. Bullock........................  41   President, Chief Executive Officer and Director
Frank J. Callaghan......................  44   Vice President, Research and Development
Richard J. Omilanowicz..................  45   Vice President, Manufacturing
Graydon E. Beatty.......................  41   Chief Technical Officer and Director
Andrew Balo.............................  50   Director of Regulatory, Clinical Affairs and Quality
                                                 Assurance
Patrick J. Wethington...................  29   Director of Marketing
Leota L. Pearson........................  38   Controller
James E. Daverman (1)(2)................  48   Director
Robert G. Hauser, M.D...................  58   Director
Ronald H. Kase (1)......................  39   Director
Steven R. LaPorte.......................  47   Director
Peter H. McNerney (1)(2)................  47   Director
</TABLE>
    
 
- ------------------------
 
(1) Member of the Compensation Committee of the Board of Directors.
 
(2) Member of the Audit Committee of the Board of Directors.
 
    JAMES W. BULLOCK has been President, Chief Executive Officer and a Director
of the Company since May 1994. In addition, Mr. Bullock served as the Chief
Financial Officer of the Company from May 1994 until May 1996. From April 1992
until joining the Company, Mr. Bullock served as President and Chief Operating
Officer of Stuart Medical, Inc., a cardiac monitoring start-up company. From
April 1990 to April 1992, Mr. Bullock served as Vice President of Sales and
Marketing of the Stackhouse Division of Bird Medical Technologies, a medical
device company. From 1978 to 1990, Mr. Bullock served in a variety of marketing
and sales management positions, most recently as Vice President of Sales, for
the Pharmaseal Division of Baxter International Inc., a medical products
company.
 
   
    FRANK J. CALLAGHAN has been Vice President of Research and Development of
the Company since November 1995. From 1987 until joining the Company, Mr.
Callaghan served as a Director of Research and Development at Telectronics
Pacing Systems, Inc., a manufacturer of cardiac rhythm management devices. From
1983 to 1987 Mr. Callaghan served in several capacities, including Manager,
Systems Technology, at Cordis Corporation, a manufacturer of angiographic and
implantable devices.
    
 
    RICHARD J. OMILANOWICZ has been Vice President of Manufacturing of the
Company since November 1994. From May 1993 until joining the Company, Mr.
Omilanowicz served as General Manager of McKechnie Plastic Components, a custom
injection molding company. From 1980 to May 1993, Mr. Omilanowicz served in
several capacities at the Pharmaseal Division of Baxter International Inc., most
recently as Director of Research, Development and Engineering.
 
    GRAYDON E. BEATTY is a founder of the Company and has been Chief Technical
Officer of the Company since May 1995 and a Director since August 1992. Since
the Company's inception in May 1992, Mr. Beatty has served in several technical
and management positions. In addition, from May 1992 until December 1993, Mr.
Beatty served as a consultant with GMN Consulting, an engineering consulting
firm, and as a consulting engineer of AngeMed, a division of Angeion Corp., a
cardiovascular device Company, from February 1992 to September 1992. Mr. Beatty
was Senior Development Engineer of Bio-Medical Design Group, Inc., an
electrophysiology system developer, from December 1991 to May 1992. From 1989 to
 
                                       35
<PAGE>
December 1991, Mr. Beatty served as Principal Research Engineer at Cardiac
Pacemakers, Inc., a cardiovascular device company.
 
   
    ANDREW K. BALO has been Vice President of Regulatory, Clinical and Quality
of the Company since October 1997. From September 1995 until joining the
Company, Mr. Balo served as Vice President, Regulatory/Clinical/Technical
Services at Pacesetter, Cardiac Rhythm Management Division of St. Jude Medical,
Inc. From July 1992 to September 1995, Mr. Balo served as Vice President
Regulatory/Clinical/ Quality of St. Jude Medical, a manufacturer of mechanical
and tissue heart valves. From 1978 to 1992, Mr. Balo served in a variety of
regulatory, clinical and quality management positions, most recently as Vice
President of Regulatory and Quality for the Operating Room Division of Baxter
International, a medical products company.
    
 
    PATRICK J. WETHINGTON has been Director of Marketing of the Company since
November 1996. From March 1994 to October 1996, Mr. Wethington was the marketing
manager for tachycardia products for Guidant/CPI's implantable cardioverter
defibrillator pulse generator and endocardial lead business. From June 1992 to
March 1994, Mr. Wethington served as a field clinical representative for
Guidant/CPI's cardiac rhythm management products. From September 1990 to June
1992, Mr. Wethington served as a sales and marketing consultant for several
businesses, including 3M, Dayton Hudson Corp. and Syner Service Corporation.
 
    LEOTA L. PEARSON has been Controller of the Company since July 1994. From
November 1993 until joining the Company, Ms. Pearson served as Controller of
General Litho Services, Inc., a printing company. Ms. Pearson completed her MBA
in June 1993. From 1983 to May 1990, Ms. Pearson served as Controller of
Orthomet, Inc., a manufacturer and distributor of orthopedic devices. Ms.
Pearson is a Certified Public Accountant.
 
    JAMES E. DAVERMAN has been a Director of the Company since July 1994. Mr.
Daverman has served as a Managing General Partner and is a founder of Marquette
Venture Partners, a venture capital investment firm, since January 1987. Mr.
Daverman is a director of Colla Genex Pharmaceuticals, Inc., a pharmaceutical
company.
 
    ROBERT G. HAUSER, M.D., has been a Director of the Company since October
1995. Dr. Hauser has been a cardiologist at the Minneapolis Heart Institute
since September 1992, and has served as President of the Cardiovascular Services
Division of Abbott Northwestern Hospital since May 1995 and Executive Director
of the Minneapolis Heart Institute since July 1994. From 1988 to July 1992, Dr.
Hauser served as President and Chief Executive Officer of Cardiac Pacemakers,
Inc., a cardiovascular device company.
 
    RONALD H. KASE has been a Director of the Company since March 1993. Mr. Kase
joined New Enterprise Associates, a venture capital investment firm, in January
1991 and is a limited partner of New Enterprise Associates V, Limited
Partnership. Mr. Kase also serves as a director of several privately held health
care companies.
 
    STEVEN R. LAPORTE has been a Director of the Company since September 1996.
Mr. LaPorte has served as Vice President and General Manager of Medtronic
CardioRhythm, an affiliate of Medtronic, since January 1994. From 1989 to
January 1994, Mr. LaPorte served as Vice President of Operations for the
Neurological Division of Medtronic, and from 1979 to 1989, as a project manager
and then Director of the Corporate Information Services division of Medtronic.
 
    PETER H. MCNERNEY has been a Director of the Company since January 1995. Mr.
McNerney has been a partner with Coral Ventures, a venture capital investment
firm, since July 1992. From 1989 to June 1992, Mr. McNerney was Managing Partner
of the Kensington Group, a health care management consulting company. Mr.
McNerney serves as a director of Biomira, Inc., a cancer immuno therapy company,
Optical Sensors, Inc., an automated blood gas sensor company, and Aksys, Ltd., a
home hemodyalisis company.
 
                                       36
<PAGE>
    The Company's Board of Directors is divided into three classes as nearly
equal in number as possible, with each class serving a three-year term. One of
the three classes of the Board of Directors is elected each year. The terms of
the Company's current Board of Directors expire as follows: Mr. Beatty and Mr.
Bullock, 1998; Dr. Hauser, Mr. McNerney and Mr. LaPorte, 1999; and Mr. Daverman
and Mr. Kase, 2000.
 
    Messrs. Kase, Daverman, McNerney and LaPorte were elected to the Board of
Directors as designees of various series of Preferred Stock pursuant to
agreements with the Company that terminated upon the consummation of the
Company's initial public offering of common stock in March 1997. The Company is
not aware of any present intention on the part of any of these individuals to
terminate his service as a director.
 
COMMITTEES
 
    The Board of Directors has established a Compensation Committee and an Audit
Committee. The Compensation Committee makes recommendations concerning executive
salaries and incentive compensation for employees of the Company, subject to
ratification by the full Board of Directors, and administers the Company's 1993
Long-Term Incentive and Stock Option Plan (the "Stock Option Plan"), the
Directors' Stock Option Plan (the "Directors' Plan") and the Company's 1997
Employee Stock Purchase Plan.
 
    The Audit Committee reviews the results and scope of the audit and other
services provided by the Company's independent auditors, as well as the
Company's accounting principles and its system of internal controls, and reports
the results of its review to the full Board of Directors and to management.
 
DIRECTORS' COMPENSATION
 
    For their services to the Company, outside directors receive stock options
under the Directors' Plan and each director is reimbursed for expenses actually
incurred in attending meetings of the Board of Directors and its committees. One
existing non-employee director has been granted options to purchase Common Stock
under the Directors' Plan. See "--Stock Plans."
 
LIMITATION OF LIABILITY
 
    The Company has adopted provisions in its Amended and Restated Certificate
of Incorporation that eliminate to the fullest extent permissible under Delaware
General Corporation Law the liability of its directors to the Company or its
stockholders for monetary damages. Such limitation of liability does not affect
the availability of equitable remedies such as injunctive relief or rescission.
The Company's amended Bylaws provide that the Company shall indemnify its
directors, officers, agents and employees to the fullest extent permitted by
Delaware General Corporation Law, including in circumstances in which
indemnification is otherwise discretionary under Delaware General Corporation
Law.
 
    At present, there is no pending litigation or proceeding involving a
director, officer, employee or other agent of the Company in which
indemnification would be required or permitted. The Company is not aware of any
threatened litigation or proceeding that may result in a claim for such
indemnification.
 
EXECUTIVE COMPENSATION
 
    SUMMARY COMPENSATION
 
    The following table sets forth the cash and noncash compensation for 1996
awarded to or earned by the Chief Executive Officer and all other executive
officers of the Company whose salary and bonus earned in 1996 exceeded $100,000
(the "Named Executive Officers"):
 
                                       37
<PAGE>
                           SUMMARY COMPENSATION TABLE
 
<TABLE>
<CAPTION>
                                                                                       LONG-TERM
                                                                                     COMPENSATION
                                                                                     -------------
                                                                                        AWARDS
                                                                                     -------------
                                                                                      SECURITIES
                                                               ANNUAL COMPENSATION    UNDERLYING
                                                              ---------------------    OPTIONS/       ALL OTHER
NAME AND PRINCIPAL POSITION                                     SALARY      BONUS     SARS(#)(1)    COMPENSATION
- ------------------------------------------------------------  ----------  ---------  -------------  -------------
<S>                                                           <C>         <C>        <C>            <C>
James W. Bullock............................................  $  180,000  $  20,000      285,000      $      --
  President, Chief Executive Officer and Director
 
Frank J. Callaghan..........................................     120,000      7,698       70,000         50,735(2)
  Vice President, Research and Development
 
Richard J. Omilanowicz......................................     119,954         --       70,000             --
  Vice President, Manufacturing
 
Graydon E. Beatty...........................................     110,000         --       25,000             --
  Chief Technical Officer and Director
</TABLE>
 
- ------------------------
 
(1) Represents options granted pursuant to the Company's Stock Option Plan.
 
(2) Represents reimbursement of relocation expenses.
 
    OPTION GRANTS
 
    The following table summarizes options granted during the year ended
December 31, 1996 to the Named Executive Officers.
 
               OPTION GRANTS DURING YEAR ENDED DECEMBER 31, 1996
 
<TABLE>
<CAPTION>
                                                                                                           POTENTIAL REALIZABLE
                                                                                                             VALUE AT ASSUMED
                                                              % OF TOTAL                                  ANNUAL RATES OF STOCK
                                                                OPTIONS                                     PRICE APPRECIATION
                                                              GRANTED TO       EXERCISE                     FOR OPTION TERM(4)
                                                  OPTIONS      EMPLOYEES         PRICE       EXPIRATION   ----------------------
NAME                                            GRANTED(1)    IN 1996(2)     PER SHARE(3)       DATE        5%($)       10%($)
- ----------------------------------------------  -----------  -------------  ---------------  -----------  ----------  ----------
<S>                                             <C>          <C>            <C>              <C>          <C>         <C>
James W. Bullock..............................      70,000          23.9%      $    2.40       06/05/06   $  105,654  $  267,749
Frank J. Callaghan............................      10,000           3.4%           5.00       12/30/06       31,445      76,687
Richard J. Omilanowicz........................      12,500           4.3%           5.00       12/30/06       39,306      99,609
Graydon E. Beatty.............................          --            --              --             --           --          --
</TABLE>
 
- ------------------------
 
(1) Each option represents the right to purchase one share of Common Stock. The
    options shown in this column are all incentive stock options granted
    pursuant to the Stock Option Plan. The options granted to Messrs. Bullock,
    Callaghan and Omilanowicz, for 70,000, 10,000 and 12,500 shares,
    respectively, become exercisable on a monthly basis over forty-eight months
    beginning six months following such grant. To the extent not already
    exercisable, the options generally become exercisable in the event of a
    merger in which the Company is not the surviving corporation, a transfer of
    all of the Company's stock, a sale of substantially all of the Company's
    assets or a dissolution or liquidation of the Company.
 
(2) In 1996, the Company granted employees options to purchase an aggregate of
    292,500 shares of Common Stock.
 
(3) The exercise price may be paid in cash, or in the case of Mr. Bullock, in
    cash, by promissory note or in shares of Common Stock with a market value as
    of the date of grant equal to the exercise price or a combination of any of
    the above.
 
                                       38
<PAGE>
(4) The compounding assumes a ten year exercise period for all options grants.
    The 5% and 10% assumed annual rates of compounded stock price appreciation
    are mandated by rules of the Securities and Exchange Commission and do not
    represent the Company's estimate or projection of the Company's future
    Common Stock prices. These amounts represent certain assumed rates of
    appreciation only. Actual gains, if any, on stock option exercises are
    dependent on the future performance of the Common Stock and overall stock
    market conditions. The amounts reflected in the table may not necessarily be
    achieved.
 
    OPTION VALUES
 
    The following table summarizes the value of options held at December 31,
1996 by the Named Executive Officers. No options held by such executive officers
were exercised during 1996.
 
                 AGGREGATED OPTION VALUES AT DECEMBER 31, 1996
 
<TABLE>
<CAPTION>
                                                    NUMBER OF SECURITIES
                                                         UNDERLYING                 VALUE OF UNEXERCISED
                                                   UNEXERCISED OPTIONS AT           IN-THE-MONEY OPTIONS
                                                      DECEMBER 31, 1996            AT DECEMBER 31, 1996(1)
                                                -----------------------------   -----------------------------
NAME                                            EXERCISABLE    UNEXERCISABLE    EXERCISABLE    UNEXERCISABLE
- ----------------------------------------------  ------------   --------------   ------------   --------------
<S>                                             <C>            <C>              <C>            <C>
James W. Bullock..............................      121,875          163,125    $  1,299,188   $   1,594,713
Frank J. Callaghan............................       16,250           53,750         173,225         586,375
Richard J. Omilanowicz........................       23,524           46,476         249,791         434,259
Graydon E. Beatty.............................       22,500            2,500         243,000          27,000
</TABLE>
 
- ------------------------
 
(1) Value based on the difference between the fair market value of the shares of
    Common Stock at December 31, 1996 ($11.00), as determined by the Board of
    Directors, and the exercise price of the options.
 
EMPLOYMENT AGREEMENTS AND CHANGE-IN-CONTROL AGREEMENTS
 
    The Company has employment agreements and change-in-control agreements with
the following executive officers.
 
    On December 28, 1994, the Company entered into an agreement with Mr. Bullock
providing for an annual salary of $170,000, benefits consistent with the
Company's employment policies and an annual minimum salary increment of five
percent on each of the first three anniversaries of the commencement of
employment. Pursuant to the agreement, the Company granted to Mr. Bullock an
option to purchase 165,000 shares of the Company's Common Stock at an exercise
price of $0.34 per share, to be vested monthly over a period of 48 months. In
addition, the agreement provides for severance pay, in the event of his
termination without cause, equal to 12 months' salary prior to completion of one
year of service, nine months' salary prior to completion of two years of
service, six months' salary prior to completion of three years of service and
three months' salary prior to completion of four years of service, and no
severance pay thereafter.
 
                                       39
<PAGE>
   
COMPENSATION COMMITTEE INTERLOCKS AND INSIDER PARTICIPATION
    
 
    Mr. Kase, Mr. McNerney and Mr. Daverman served as members of the Company's
Compensation Committee during 1995. Mr. Kase is a limited partner in New
Enterprise Associates V, Limited Partnership. New Enterprise Associates V,
Limited Partnership is affiliated with ONSET Enterprise Associates, L.P.,
Chemicals & Materials Enterprise Associates, Limited Partnership and Catalyst
Ventures. Mr. Daverman is the Managing General Partner of Marquette Venture
Partners II, L.P. and MVP II Affiliates Fund, L.P. Mr. McNerney is a Partner of
Coral Partners IV, Limited Partnership. See "Principal Stockholders."
 
    In March 1993, the Company sold 775,000 shares of Series A Preferred Stock
(convertible into an aggregate of 387,500 shares of Common Stock) to New
Enterprise Associates V, Limited Partnership Catalyst Ventures, ONSET Enterprise
Associates, L.P. and Chemicals & Materials Enterprise Associates pursuant to
preferred stock purchase agreements on substantially similar terms as were sold
to non-affiliated purchasers. See "Certain Transactions."
 
    In October 1993 and November 1993, the Company borrowed an aggregate of
$250,000 from Series A Preferred Stockholders, payable in January 1994 or
convertible into Series B Preferred Stock at a price equal to the price paid per
share by investors purchasing Series B Preferred Stock. In December 1993, the
investors exercised the conversion option, and the Company issued 147,058 shares
of Series B Preferred Stock (convertible into an aggregate of 73,529 shares of
Common Stock). See "Certain Transactions."
 
    From December 1993 through March 1995, the Company sold 6,682,506 shares of
Series B Preferred Stock (convertible into an aggregate of 3,341,253 shares of
Common Stock) to New Enterprise Associates V, Limited Partnership, ONSET
Enterprise Associates, L.P., Chemicals & Materials Enterprise Associates,
Limited Partnership, Catalyst Ventures, Sprout Capital VI, L.P., DLJ Capital
Corporation, Marquette Venture Partners II, L.P., MVP II Affiliates Fund, L.P.
and Coral Partners IV, Limited Partnership pursuant to preferred stock purchase
agreements on substantially similar terms as were sold to non-affiliated
purchasers. See "Certain Transactions."
 
STOCK PLANS
 
    STOCK OPTION PLAN
 
    Pursuant to the 1993 Long-Term Stock Option Plan (the "Stock Option Plan"),
directors, officers, other employees and consultants of the Company may receive
options to purchase Common Stock. The Stock Option Plan provides for the grant
of both incentive stock options intended to qualify for preferential tax
treatment under Section 422 of the Internal Revenue Code of 1986, as amended
("Incentive Stock Options"), and nonqualified stock options that do not qualify
for such treatment. Only employees of the Company, including officers and
directors who are employees of the Company, are eligible to receive Incentive
Stock Options. The exercise price of all incentive stock options granted under
the Stock Option Plan must equal or exceed the fair market value of the Common
Stock at the time of grant. The Stock Option Plan also provides for grants of
stock appreciation rights, restricted stock awards and performance awards. The
Stock Option Plan is administered by the Compensation Committee.
 
   
    A total of 1,500,000 shares of Common Stock have been reserved for issuance
under the Stock Option Plan. As of September 30, 1997, the Company had
outstanding options to purchase an aggregate of (i) 853,361 shares, at a
weighted average exercise price of $2.35 per share, pursuant to the Stock Option
Plan and (ii) no shares granted outside of the Stock Option Plan.
    
 
    DIRECTORS' PLAN
 
    The Company's Directors' Stock Option Plan (the "Directors' Plan") provides
for the automatic grant of nonstatutory stock options to purchase 10,000 shares
of Common Stock to nonemployee directors at the time of their election as
director, and an option to purchase 5,000 shares of Common Stock on the date of
 
                                       40
<PAGE>
each subsequent annual shareholder meeting, subject to certain limitations.
Options granted on the date an individual is elected as a director of the
Company become vested and thereby exercisable with respect to 33 1/3% of the
shares on the date of such election, 33 1/3% of such shares on the twelve month
anniversary date after such election and 33 1/3% of such shares on the date of
the second twelve month anniversary date after such election; provided, however,
that an unvested portion of such option grant shall only vest so long as the
nonemployee director remains a director on the date such portion vests, and that
vested options shall terminate seven years after the date a director ceases to
be a director of the Company or on the date of termination of the option,
whichever occurs earlier. Options granted on the date of each annual meeting of
shareholders become exercisable six months after the date of grant. The option
price for nonemployee directors is equal to the fair market value of a share of
Common Stock as of the date of grant. The Company has reserved a total of
200,000 shares of Common Stock for issuance under the Director's Plan, all of
which are currently available for future grant.
 
    EMPLOYEE STOCK PURCHASE PLAN
 
   
    The Company's 1997 Employee Stock Purchase Plan (the "Stock Purchase Plan")
covers an aggregate of 200,000 shares of Common Stock. The Stock Purchase Plan
is intended to qualify as an employee stock purchase plan within the meaning of
Section 423 of the Code. All employees that have met the service eligibility
requirements will be eligible to participate in the Stock Purchase Plan.
Participating employees will be able to direct the Company to make payroll
deductions of one to fifteen percent of their compensation during a purchase
period for the purchase of shares under the Stock Purchase Plan. The purchase
period for any offering, with the exception of the initial offering period, will
be no more than three months. The Stock Purchase Plan provides participating
employees with the right, subject to certain limitations, to purchase the
Company's Common Stock at a price equal to 85% of the lesser of the fair market
value of the Company's Common Stock on the first day or the last day of the
applicable purchase period, except that the price on the first day of the
initial purchase period is $9.00, the price per share at which the shares of the
Common Stock were first sold to the public in the Company's initial public
offering of Common Stock. The Stock Purchase Plan will terminate on such date as
the Board of Directors may determine, or automatically as of the date on which
all of the shares the Company has reserved for purchase under the Stock Purchase
Plan have been sold.
    
 
                                       41
<PAGE>
                              CERTAIN TRANSACTIONS
 
    Since March 1993, the Company has sold shares of Preferred Stock and Common
Stock as follows: in March 1993, the Company issued 775,000 shares of Series A
Preferred Stock at a price of $1.00 per share; in December 1993, the Company
issued 2,882,354 shares of Series B Preferred Stock at a price of $1.70 per
share; in December 1993 (as described below), the Company issued 147,058 shares
of Series B Preferred Stock in connection with the conversion of loans in the
aggregate amount of $250,000 made by certain Series A Preferred Stockholders to
the Company; in January 1995 and in March 1995, the Company issued 3,588,388 and
64,706 shares of Series B Preferred Stock, respectively, at a price of $1.70 per
share; in April 1996, the Company issued 1,953,700 shares of Series C Preferred
Stock at a price of $5.12 per share; and in March 1997 the Company issued
2,250,000 shares of Common Stock at a price of $9.00 per share in an initial
public offering and 750,000 shares of Common Stock to the Selling Stockholder in
a concurrent private placement. Each share of the Company's Preferred Stock
converted into one-half share of Common Stock upon completion of the Company's
initial public offering, as a result of the one-for-two reverse stock split of
the Common Stock. Certain of these shares were sold or issued to the Company's
five percent stockholders and entities affiliated with directors. The Company
sold such securities pursuant to stock purchase agreements on substantially
similar terms as were sold to nonaffiliated purchasers. The following table
summarizes the Series A, Series B and Series C Preferred Stock and Common Stock
purchased by the Company's five percent stockholders and entities affiliated
with directors, and their affiliates:
 
<TABLE>
<CAPTION>
                                            COMMON STOCK ISSUED UPON
                                          CONVERSION OF PREFERRED STOCK
                                         -------------------------------
STOCKHOLDERS                             SERIES A   SERIES B   SERIES C    COMMON
- ---------------------------------------  ---------  ---------  ---------  ---------
<S>                                      <C>        <C>        <C>        <C>
New Enterprise Associates V, Limited
  Partnership and affiliated entities
  (1)..................................    362,500  1,419,118         --         --
Marquette Venture Partners II, L.P. and
  MVP II Affiliates Fund, L.P..........         --    735,294         --         --
Sprout Capital VI, L.P. and DLJ Capital
  Corporation..........................         --    482,347         --         --
Coral Partners IV, Limited
  Partnership..........................         --    441,177         --         --
Medtronic Asset Management, Inc........         --         --    976,850    750,000
</TABLE>
 
- ------------------------
 
(1) Includes shares held by ONSET Enterprise Associates, L.P., Catalyst Ventures
    and Chemicals & Materials Enterprise Associates, Limited Partnership.
 
    The investors in all of the above transactions have rights to require the
Company to register shares pursuant to the Securities Act. See "Shares Eligible
for Future Sale."
 
    Mr. Kase, a director of the Company, is a limited partner in New Enterprise
Associates V, Limited Partnership.
 
    Mr. Daverman, a director of the Company, is the Managing General Partner and
founder of Marquette Venture Partners II, L.P. and MVP II Affiliates Fund, L.P.
 
    Mr. McNerney, a director of the Company, is a partner of Coral Management
Partners IV, the General Partner of Coral Partners IV, Limited Partnership.
 
    Mr. LaPorte, a director of the Company, is Vice President and General
Manager of Medtronic CardioRhythm, an affiliate of Medtronic.
 
    The Company paid $694,000, $475,000 and $59,000 in 1994, 1995 and 1996,
respectively, to Novel Biomedical, Inc. in connection with research and
development activities performed for the Company. The owner of Novel Biomedical,
Inc., Jonathan Kagan, is a founder and stockholder of the Company.
 
                                       42
<PAGE>
    On October 29, 1993 and November 29, 1993, the Company borrowed a total of
$250,000 from certain Series A Preferred stockholders through the issuance of
promissory notes. The promissory notes earned interest at a rate of 7.00% and
were convertible into shares of Series B Preferred Stock at a price equal to the
price paid per share by investors purchasing Series B Preferred Stock. The notes
were converted into 147,058 shares of Series B Preferred Stock on December 23,
1993.
 
   
    In April 1996, the Company entered into an Investment Agreement (the
"Investment Agreement") with a wholly-owned subsidiary of Medtronic, pursuant to
which the Company sold to Medtronic 1,953,700 shares of the Company's Series C
Preferred Stock for a purchase price of $10 million. See "Principal
Stockholders." Each share of Series C Preferred Stock issued to Medtronic
automatically converted to one-half share of Common Stock upon completion of the
Company's initial public offering, as a result of the one-for-two reverse stock
split of the Common Stock. Pursuant to the Investment Agreement, the Company has
granted Medtronic a right of first offer with respect to the exclusive
distribution of the EnSite System and related products in territories outside of
North America. Pursuant to such right of first offer, the Company and Medtronic
entered into a seven-year distribution agreement in September 1997 to market the
EnSite System in Europe, Japan and the Middle East. See "Business--Sales and
Marketing." The Company also granted Medtronic certain rights to have the shares
of Common Stock issued upon conversion of the Series C Preferred Stock
registered under the federal securities laws. Medtronic currently owns 1,726,850
shares of Common Stock of the Company, which represents approximately 19.3% of
the Company's outstanding Common Stock. See "Selling Stockholder" and "Principal
Stockholders."
    
 
                                       43
<PAGE>
                             PRINCIPAL STOCKHOLDERS
 
    The following table sets forth certain information regarding beneficial
ownership of the Common Stock, as of the date hereof by: (i) each person who is
known by the Company to beneficially own more than five percent of the Common
Stock, (ii) each of the Company's directors, (iii) each of the Named Executive
Officers and (iv) all directors and executive officers of the Company as a
group:
 
   
<TABLE>
<CAPTION>
                                                                SHARES
                                                              BENEFICIALLY PERCENTAGE OF OUTSTANDING
NAME AND ADDRESS                                               OWNED(1)          SHARES OWNED
- ------------------------------------------------------------  -----------  -------------------------
<S>                                                           <C>          <C>
Medtronic Asset Management, Inc. ...........................   1,726,850                19.3%
  7000 Central Avenue NE
  Minneapolis, MN 55432
Entities affiliated with New Enterprise Associates V,          1,319,853                14.8
  Limited Partnership (2) ..................................
  2490 Sand Hill Road
  Menlo Park, CA 94025
Marquette Venture Partners II, L.P. (3) ....................     735,294                 8.2
  520 Lake Cook Road, Suite 450
  Deerfield, IL 60015
Sprout Capital VI, L.P. (4) ................................     482,347                 5.4
  3000 Sand Hill Road
  Building 4, Suite 270
  Menlo Park, CA 94025-7114
ONSET Enterprises, L.P. (5) ................................     461,765                 5.2
  2490 Sand Hill Road
  Menlo Park, CA 94025
Coral Partners IV, .........................................     441,177                 4.9
  Limited Partnership
  60 South Sixth Street Suite 3510
  Minneapolis, MN 55402
Graydon E. Beatty (6).......................................     275,000                 3.1
James W. Bullock (7)........................................     170,938                 1.9
James E. Daverman (8).......................................     745,294                 8.3
Robert G. Hauser, M.D. (7)..................................      16,667                   *
Ronald H. Kase (9)..........................................      10,000                   *
Steven R. LaPorte (10)......................................      10,000                   *
Peter H. McNerney (11)......................................     451,177                 5.0
Frank J. Callaghan (7)......................................      32,084                   *
Richard J. Omilanowicz (7)..................................      37,682                   *
All executive officers and directors as a group (10            5,247,310                58.7
  persons)(12)..............................................
</TABLE>
    
 
- ------------------------
 
 *  Less than 1%.
 
(1) Beneficial ownership is determined in accordance with rules of the
    Securities and Exchange Commission, and includes generally voting power
    and/or investment power with respect to securities. Shares of Common Stock
    subject to options or warrants currently exercisable or exercisable within
    60 days of the date hereof ("Currently Exercisable Options") are deemed
    outstanding for computing the percentage benefically owned by the person
    holding such options but are not deemed outstanding for computing the
    percentage beneficially owned by any other person. Except as indicated by
    footnote, the Company believes that the persons named in this table, based
    on information provided by such persons, have sole voting and investment
    power with respect to the shares of Common Stock indicated.
 
                                       45
<PAGE>
(2) Represents 947,794 shares held by New Enterprises Associates V, Limited
    Partnership, 233,824 shares held by Chemicals & Materials Enterprise
    Associates, Limited Partnership and 138,236 shares held by Catalyst
    Ventures.
 
(3) Includes 20,426 shares held by MVP II Affiliates Fund, L.P.
 
(4) Includes 65,986 shares held by DLJ Capital Corporation.
 
(5) An affiliate of New Enterprise Associates.
 
(6) Includes 24,584 shares issuable pursuant to Currently Exercisable Options.
 
(7) Represents shares issuable pursuant to Currently Exercisable Options.
 
(8) Includes 735,294 shares beneficially owned by Marquette Venture Partners II,
    L.P. and MVP II Affiliates Fund, L.P. with respect to which Mr. Daverman has
    voting and investment power. See Note 4 above. Mr. Daverman is a Managing
    General Partner of Marquette Venture Partners II, L.P. Mr. Daverman
    disclaims beneficial ownership of these shares, except to the extent of his
    proportionate interest in Marquette Venture Partners II, L.P.
 
(9) Excludes shares beneficially owned by entities affiliated with New
    Enterprise Associates. See Notes 2 and 5. Mr. Kase is a limited partner of
    New Enterprise Associates V, Limited Partnership. Mr. Kase disclaims
    beneficial ownership of these shares, except to the extent of his
    proportionate interest in New Enterprise Associates V, Limited Partnership.
 
(10) Excludes shares beneficially owned by Medtronic Asset Management, Inc. Mr.
    LaPorte is Vice President and General Manager of Medtronic CardioRhythm, an
    affiliate of Medtronic. Mr. LaPorte disclaims beneficial ownership of these
    shares.
 
(11) Includes 441,177 shares beneficially owned by Coral Partners IV, Limited
    Partnership with respect to which Mr. McNerney has voting and investment
    power. Mr. McNerney is a partner of Coral Management Partners IV, the
    General Partner of Coral Partners IV, Limited Partnership. Mr. McNerney
    disclaims beneficial ownership of these shares, except to the extent of his
    proportionate interest in Coral Partners IV, Limited Partnership.
 
   
(12) See Notes 6, 7, 8, 9, 10 and 11 above.
    
 
                                       46
<PAGE>
                          DESCRIPTION OF CAPITAL STOCK
 
   
    The total number of shares of all classes of stock which the Company has
authority to issue is 40,000,000 shares of Common Stock, $.01 par value, and
10,000,000 shares of undesignated preferred stock, $.01 par value. As of
December 31, 1997, there were 8,934,441 shares of Common Stock outstanding,
which were held of record by 130 stockholders, and no shares of undesignated
preferred stock outstanding.
    
 
COMMON STOCK
 
    The holders of Common Stock are entitled to one vote for each share held of
record on all matters submitted to a vote of stockholders. There is no
cumulative voting for the election of directors so that holders of more than 50%
of the outstanding Common Stock of the Company can elect all directors. Subject
to preferences that may be applicable to any outstanding preferred stock,
holders of Common Stock are entitled to receive ratably such dividends as may be
declared by the Board of Directors of the Company out of funds legally available
therefor and in liquidation proceedings. Holders of Common Stock have no
preemptive or subscription rights and there are no redemption rights with
respect to such shares. The outstanding shares of Common Stock are fully paid
and nonassessable.
 
PREFERRED STOCK
 
    The Company's Board of Directors is authorized, without further stockholder
action, to issue preferred stock in one or more series and to fix the voting
rights, liquidation preferences, dividend rights, repurchase rights, conversion
rights, redemption rights and terms, including sinking fund provisions, and
certain other rights and preferences, of the preferred stock.
 
    Although there is no current intention to do so, the Board of Directors of
the Company may, without stockholder approval, issue shares of a class or series
of preferred stock with voting and conversion rights which could adversely
affect the voting power or dividend rights of the holders of Common Stock and
may have the effect of delaying, deferring or preventing a change in control of
the Company.
 
WARRANTS AND OPTIONS
 
    The Company has issued a warrant to purchase 5,000 shares of Common Stock at
an exercise price of $.10 per share to Tikkun Resource Development. Such warrant
is currently exercisable for 2,500 shares of Common Stock at an exercise price
of $.20 per share and expires in November 2003.
 
    The Company has issued, in connection with equipment leasing arrangements, a
warrant to purchase 46,607 shares of its Common Preferred Stock at an exercise
price of $3.40 per share and a warrant to purchase 7,500 shares of its Common
Stock at an exercise price of $10.24 per share. Such warrants are currently
exercisable and expire in November 2004 and August 2006, respectively.
 
   
    As of September 30, 1997, the Company had issued options to purchase a total
of 853,361 shares of Common Stock at a weighted average exercise of $2.35 per
share. See "Management--Stock Plans."
    
 
    The above described warrants and all options granted under the Stock Option
Plan provide for antidilution adjustments in the event of certain mergers,
consolidations, reorganizations, recapitalizations, stock dividends, stock
splits or other changes in the corporate structure of the Company.
 
PROVISIONS OF THE COMPANY'S AMENDED AND RESTATED CERTIFICATE OF INCORPORATION
  AND AMENDED BYLAWS AND THE DELAWARE GENERAL CORPORATION LAW
 
    The existence of authorized but unissued preferred stock, described above,
and certain provisions of the Company's Amended and Restated Certificate of
Incorporation and Amended Bylaws and Delaware law, described below, could have
an antitakeover effect. These provisions are intended to provide
 
                                       47
<PAGE>
management flexibility, to enhance the likelihood of continuity and stability in
the composition of the Company's Board of Directors and in the policies
formulated by the Board of Directors and to discourage an unsolicited takeover
of the Company if the Board of Directors determines that such a takeover is not
in the best interests of the Company and its stockholders. However, these
provisions could have the effect of discouraging certain attempts to acquire the
Company which could deprive the Company's stockholders of opportunities to sell
their shares of Common Stock at prices higher than prevailing market prices.
 
    Pursuant to the Amended Bylaws, the Board of Directors of the Company is
divided into three classes serving staggered three-year terms. As a result, at
least two shareholders' meetings will generally be required for shareholders to
effect a change in control of the Board of Directors.
 
    The Company is subject to the "Business Combination" provisions of the
Delaware General Corporation Law. In general, such provisions prohibit a
publicly held Delaware corporation from engaging in various "business
combination" transactions with any "interested stockholder" for a period of
three years after the date of the transaction in which the person became an
"interested stockholder," unless (i) the transaction is approved by the Board of
Directors prior to the date the interested stockholder obtained such status,
(ii) upon consummation of the transaction which resulted in the stockholder
becoming an "interested stockholder," the "interested stockholder" owned at
least 85% of the voting stock of the corporation outstanding at the time the
transaction commenced, excluding for purposes of determining the number of
shares outstanding those shares owned by (a) persons who are directors and also
officers and (b) employee stock plans in which employee participants do not have
the right to determine confidentially whether shares held subject to the plan
will be tendered in a tender or exchange offer, or (iii) on or subsequent to
such date the "business combination" is approved by the board of directors and
authorized at an annual or special meeting of stockholders by the affirmative
vote of at least 66 2/3% of the outstanding voting stock which is not owned by
the "interested stockholder." A "business combination" is defined to include
mergers, asset sales and other transactions resulting in a financial benefit to
a stockholder. In general, an "interested stockholder" is a person who, together
with affiliates and associates, owns (or within three years, did own) 15% or
more of a corporation's voting stock. The Company's stockholders which owned 15%
of the corporation's voting stock on the date of this prospectus are not
interested stockholders subject to the "Business Combination" provisions of the
Delaware General Corporation Law. The statute could prohibit or delay mergers or
other takeover or change in control attempts with respect to the Company and,
accordingly, may discourage attempts to acquire the Company.
 
TRANSFER AGENT AND REGISTRAR
 
    The Transfer Agent and Registrar with respect to the Common Stock is Norwest
Bank Minnesota, National Association.
 
                                       48
<PAGE>
                        SHARES ELIGIBLE FOR FUTURE SALE
 
    Future sales of substantial amounts of Common Stock in the public market
could adversely affect the prevailing market price and impair the Company's
ability to raise additional funds.
 
   
    As of December 31, 1997, the Company had outstanding an aggregate of
8,934,441 shares of Common Stock. Of the total outstanding shares of Common
Stock, 3,175,410 shares (including the 750,000 shares offered hereby) are freely
tradeable without restriction or further registration under the Securities Act,
unless held by "affiliates" of the Company, as that term is defined in Rule 144
under the Securities Act (whose sales would be subject to certain volume
limitations and other restrictions described below).
    
 
   
    The remaining 5,759,031 shares of Common Stock are "restricted securities"
as that term is defined in Rule 144 under the Securities Act. Approximately
4,100,551 of the restricted shares are eligible for sale, subject to compliance
with the volume limitations and other restrictions of Rule 144, and
approximately 538,126 of the restricted shares are eligible for immediate sale
without restriction pursuant to Rule 144(k).
    
 
   
    In general, under Rule 144, as in effect upon expiration of the contractual
restrictions described above, if at least one year has elapsed from the date
that shares of Common Stock were acquired from the Company or an affiliate of
the Company, then the holder is entitled to sell in "brokers' transactions" or
to market makers, within any three-month period commencing 90 days after the
date of this Prospectus, a number of shares that does not exceed the greater of
(i) one percent of the then outstanding shares of Common Stock (89,334 shares as
of December 31, 1997) or (ii) generally, the average weekly trading volume in
the Common Stock during the four calendar weeks preceding the filing of a Form
144 with respect to such sale, subject to certain other limitations and
restrictions. In addition, a person who is not deemed to have been an affiliate
of the Company at any time during the three months preceding a sale, and who has
beneficially owned the shares proposed to be sold for at least two years, would
be entitled to sell such shares under Rule 144(k) without regard to the
requirements described above.
    
 
   
    The Company has previously filed registration statements under the
Securities Act covering 1,500,000, 200,000 and 200,000 shares of Common Stock
reserved for issuance under the Stock Option Plan, the Stock Purchase Plan and
the Directors' Plan, respectively. See "Management--Stock Plans."
    
 
   
    In addition, the holders of approximately 4,705,603 shares of Common Stock
(the "Registrable Securities") are entitled to certain rights to cause the
Company to register the sale of such shares under the Securities Act. If the
Company proposes to register any of its securities under the Securities Act for
its own account, holders of Registrable Securities are entitled to notice of
such registration and are entitled to include Registrable Securities therein,
provided, among other conditions, that the underwriters of any such offering
have the right to limit the number of shares included in such registration. The
holders of the Registrable Securities may require the Company to prepare and
file a registration statement under the Securities Act at its expense (a "Demand
Registration"), and the Company is required to use its best efforts to effect
such Demand Registration, subject to certain conditions and limitations. Holders
of Registrable Securities with an aggregate proposed offering price of not less
than $500,000 may require the Company to file not more than two additional
registration statements on Form S-3 under the Securities Act, subject to certain
conditions and limitations. Registration of such shares would result in such
shares becoming freely tradeable without restriction under the Securities Act
(except for shares purchased by affiliates of the Company) immediately upon the
effectiveness of such registration.
    
 
    The Company can make no prediction as to the effect, if any, that sales of
shares of Common Stock or the availability of Common Stock for sale will have on
the market price prevailing from time to time. Nevertheless, sales of
substantial amounts of the Common Stock in the public markets or the perception
that such sales will occur could adversely affect the market price or the future
ability to raise capital through an offering of its equity securities. See "Risk
Factors--Shares Eligible for Future Sale; Registration Rights."
 
                                       49
<PAGE>
                               VALIDITY OF SHARES
 
    The validity of the securities offered hereby will be passed upon for the
Company by Dorsey & Whitney LLP, Minneapolis, Minnesota.
 
                                    EXPERTS
 
    The financial statements as of December 31, 1995 and 1996, and for each of
the three years in the period ended December 31, 1996, and the period from May
21, 1992 (inception) to December 31, 1996, included in this Prospectus have been
audited by Ernst & Young LLP, independent auditors, as set forth in their report
thereon appearing elsewhere herein and in the Registration Statement, and such
financial statements are included in reliance upon such report given upon the
authority of such firm as experts in accounting and auditing.
 
                             AVAILABLE INFORMATION
 
    The Company is subject to the informational requirements of the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), and in accordance
therewith files reports, proxy statements and other information with the
Securities and Exchange Commission (the "Commission"). Such reports, proxy
statements and other information filed by the Company can be inspected and
copied at the public reference facilities of the Commission at 450 Fifth Street,
N.W., Washington, D.C. 20549, and at the Commission's regional offices at 7
World Trade Center, Suite 1300, New York, New York 10048 and CitiCorp Center,
500 West Madison Street, Suite 1400, Chicago, Illinois 60661. Copies of such
materials can be obtained from the Public Reference Section of the Commission at
450 Fifth Street, N.W., Washington, D.C. 20549, at prescribed rates. The
Commission also maintains a World Wide Web site which provides on-line access to
registration statements, reports, proxy and information statements and other
information regarding registrants that file electronically with the Commission
at the address "http://www.sec.gov." This Prospectus does not contain all the
information set forth in the Registration Statement and exhibits thereto which
the Company has filed with the Commission under the Securities Act of 1933, as
amended (the "Securities Act"), and to which reference is hereby made.
 
                                       50
<PAGE>
                          ENDOCARDIAL SOLUTIONS, INC.
 
                         INDEX TO FINANCIAL STATEMENTS
 
<TABLE>
<CAPTION>
                                                                                                               PAGE
                                                                                                             ---------
<S>                                                                                                          <C>
Report of Independent Auditors.............................................................................     F-2
 
Balance Sheets.............................................................................................     F-3
 
Statements of Operations...................................................................................     F-4
 
Statement of Changes in Stockholders' Equity...............................................................     F-5
 
Statements of Cash Flows...................................................................................     F-8
 
Notes to Financial Statements..............................................................................     F-9
</TABLE>
 
                                      F-1
<PAGE>
                         REPORT OF INDEPENDENT AUDITORS
 
Board of Directors and Stockholders
Endocardial Solutions, Inc.
 
    We have audited the accompanying balance sheets of Endocardial Solutions,
Inc. (a development stage company) as of December 31, 1995 and 1996, and the
related statements of operations, changes in stockholders' equity and cash flows
for each of the three years in the period ended December 31, 1996, and for the
period from May 21, 1992 (inception) to December 31, 1996. These financial
statements are the responsibility of the Company's management. Our
responsibility is to express an opinion on these financial statements based on
our audits.
 
    We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.
 
    In our opinion, the financial statements referred to above present fairly,
in all material respects, the financial position of Endocardial Solutions, Inc.
at December 31, 1995 and 1996, and the results of its operations and its cash
flows for each of the three years in the period ended December 31, 1996, and for
the period from May 21, 1992 (inception) to December 31, 1996, in conformity
with generally accepted accounting principles.
 
                                          Ernst & Young LLP
 
Minneapolis, Minnesota
January 9, 1997
 
                                      F-2
<PAGE>
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                                 BALANCE SHEETS
 
<TABLE>
<CAPTION>
                                                            DECEMBER 31,
                                                      ------------------------   SEPTEMBER
                                                         1995         1996       30, 1997
                                                      -----------  -----------  -----------
                                                                                (UNAUDITED)
<S>                                                   <C>          <C>          <C>
                                          ASSETS
Current assets:
  Cash and cash equivalents.........................  $ 1,863,788  $ 6,157,491  $ 5,971,430
  Short-term investments............................      --           --        19,153,144
  Inventories.......................................      --           --            88,613
  Prepaid expenses and other current assets.........       72,211       75,053      232,948
                                                      -----------  -----------  -----------
Total current assets................................    1,935,999    6,232,544   25,446,135
Furniture and equipment.............................      944,136    1,496,404    2,320,145
Less accumulated depreciation.......................      381,067      656,695      973,955
                                                      -----------  -----------  -----------
                                                          563,069      839,709    1,346,190
Deposits............................................       47,034       81,709       81,709
Patents, less accumulated amortization
  (1995--$22,019; 1996--$37,339 and September 30,
  1997--$50,069)....................................       48,851       46,164       36,886
                                                      -----------  -----------  -----------
Total assets........................................  $ 2,594,953  $ 7,200,126  $26,910,920
                                                      -----------  -----------  -----------
                                                      -----------  -----------  -----------
 
                           LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
  Accounts payable..................................  $   233,761  $   265,856  $   598,498
  Accrued salaries and expenses.....................       77,585      164,766      374,243
  Current portion of long-term debt and capital
    lease obligations...............................      207,173      252,955      397,528
                                                      -----------  -----------  -----------
Total current liabilities...........................      518,519      683,577    1,370,269
Long-term debt and capital lease obligations........      160,470      302,291      482,690
Stockholders' equity:
  Undesignated Preferred Stock, par value...........
    $.01 per share:
      Authorized shares--10,000,000
      Issued and outstanding shares--none...........      --           --           --
  Convertible Preferred Stock, Series A through D,
    par value $.01 per share:
    Authorized shares--1995--7,574,096;
      1996--9,527,796; September 30, 1997--None
    Issued and outstanding shares--June 30,
      1997--None; December 31, 1996--9,411,206;
      September 30, 1997--None......................       74,575       94,112      --
  Common Stock, $.01 par value:
    Authorized shares--1995 and 1996--17,000,000;
      September 30, 1997--40,000,000................
    Issued and outstanding shares--1995--1,028,563;
      1996--1,053,428; September
      30,1997--8,898,047............................       10,286       10,534       88,980
  Additional paid-in capital........................   11,973,840   23,444,359   48,131,838
  Deficit accumulated during the development
    stage...........................................  (10,142,737) (16,623,338) (22,754,145)
  Deferred compensation.............................      --          (711,409)    (408,712)
                                                      -----------  -----------  -----------
Total stockholders' equity..........................    1,915,964    6,214,258   25,057,961
                                                      -----------  -----------  -----------
Total liabilities and stockholders' equity..........  $ 2,594,953  $ 7,200,126  $26,910,920
                                                      -----------  -----------  -----------
                                                      -----------  -----------  -----------
</TABLE>
 
                            See accompanying notes.
 
                                      F-3
<PAGE>
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                            STATEMENTS OF OPERATIONS
 
   
<TABLE>
<CAPTION>
                                                                                                                 PERIOD FROM
                                                                                     NINE MONTHS ENDED           MAY 21, 1992
                                       YEAR ENDED DECEMBER 31,                         SEPTEMBER 30,            (INCEPTION)TO
                           ------------------------------------------------   -------------------------------   SEPTEMBER 30,
                                1994             1995             1996             1996             1997             1997
                           --------------   --------------   --------------   --------------   --------------   --------------
                                                                               (UNAUDITED)      (UNAUDITED)      (UNAUDITED)
<S>                        <C>              <C>              <C>              <C>              <C>              <C>
Operating expenses:
  Research and
    development..........  $    3,351,600   $    3,638,868   $    4,424,905   $   3,037,002    $   4,404,723    $  16,523,045
  General and
    administrative.......         858,527        1,087,905        1,911,242       1,179,084        1,991,554        6,189,111
  Sales and marketing....         281,564          122,848          373,348         136,508          517,134        1,334,112
                           --------------   --------------   --------------   --------------   --------------   --------------
Operating loss...........      (4,491,691)      (4,849,621)      (6,709,495)     (4,352,594)      (6,913,411)     (24,046,268)
Other income (expense):
  Interest income........          89,592          198,878          293,585         210,607          845,917        1,436,233
  Interest expense.......          (6,132)         (82,993)         (64,691)        (40,682)         (63,313)        (220,341)
                           --------------   --------------   --------------   --------------   --------------   --------------
                                   83,460          115,885          228,894         169,925          782,604        1,215,892
                           --------------   --------------   --------------   --------------   --------------   --------------
Net loss for the period
  and deficit accumulated
  during development
  stage..................  $   (4,408,231)  $   (4,733,736)  $   (6,480,601)  $  (4,182,669)   $  (6,130,807)   $ (22,830,376)
                           --------------   --------------   --------------   --------------   --------------   --------------
                           --------------   --------------   --------------   --------------   --------------   --------------
Net loss per share:
  Primary................           (3.12)           (3.33)           (4.53)          (2.93)            (.96)          (10.83)
                           --------------   --------------   --------------   --------------   --------------   --------------
                           --------------   --------------   --------------   --------------   --------------   --------------
  Fully diluted..........           (1.33)            (.95)           (1.12)           (.74)            (.78)           (5.60)
                           --------------   --------------   --------------   --------------   --------------   --------------
                           --------------   --------------   --------------   --------------   --------------   --------------
Weighted average number
  of common shares
  outstanding
  Primary................       1,411,168        1,422,757        1,429,239       1,427,655        6,373,191        2,108,184
                           --------------   --------------   --------------   --------------   --------------   --------------
                           --------------   --------------   --------------   --------------   --------------   --------------
  Fully diluted..........       3,313,374        4,999,298        5,809,225       5,623,156        7,890,739        4,077,520
                           --------------   --------------   --------------   --------------   --------------   --------------
                           --------------   --------------   --------------   --------------   --------------   --------------
</TABLE>
    
 
                            See accompanying notes.
 
                                      F-4
<PAGE>
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
                  STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY
<TABLE>
<CAPTION>
                                            SERIES A PREFERRED          SERIES B              SERIES C
                                                  STOCK             PREFERRED STOCK        PREFERRED STOCK
                                          ----------------------  --------------------  ---------------------
                                           SHARES      AMOUNT      SHARES     AMOUNT     SHARES      AMOUNT
                                          ---------  -----------  ---------  ---------  ---------  ----------
<S>                                       <C>        <C>          <C>        <C>        <C>        <C>
Balance at May 21, 1992 (inception).....     --       $  --          --      $  --         --      $   --
  Original issuance of Common Stock at
    $.01 per share......................     --          --          --         --         --          --
  Sale of Common Stock at $.12 per share
    at various dates throughout the
    period..............................     --          --          --         --         --          --
  Net loss..............................     --          --          --         --         --          --
                                          ---------  -----------  ---------  ---------  ---------  ----------
Balance at December 31, 1992............     --          --          --         --         --          --
  Sale of Common Stock at $.60 per share
    in January 1993.....................     --          --          --         --         --          --
  Recapitalization resulting from
    election of C Corporation status....     --          --          --         --         --          --
  Sale of Series A Preferred Stock at
    $1.00 per share in March 1993.......    775,000       7,750      --         --         --          --
  Sale of Series B Preferred Stock at
    $1.70 in December 1993, net of
    offering costs......................     --          --       2,882,354     28,823     --          --
  Conversion of notes payable to Series
    B Preferred Stock at $1.70 per share
    in December 1993....................     --          --         147,058      1,471     --          --
  Exercise of stock options.............     --          --          --         --         --          --
  Net loss..............................     --          --          --         --         --          --
                                          ---------  -----------  ---------  ---------  ---------  ----------
Balance at December 31, 1993 (brought
  forward)..............................    775,000       7,750   3,029,412     30,294     --          --
 
<CAPTION>
                                                                                  DEFICIT
                                                                                ACCUMULATED
                                                COMMON STOCK        ADDITIONAL   DURING THE
                                          ------------------------   PAID-IN    DEVELOPMENT     DEFERRED
                                            SHARES       AMOUNT      CAPITAL       STAGE      COMPENSATION     TOTAL
                                          ----------   -----------  ----------  ------------  -------------  ----------
<S>                                       <C>          <C>          <C>         <C>           <C>            <C>
Balance at May 21, 1992 (inception).....      --        $  --       $   --       $   --        $   --        $   --
  Original issuance of Common Stock at
    $.01 per share......................     750,000        7,500       --           --            --             7,500
  Sale of Common Stock at $.12 per share
    at various dates throughout the
    period..............................     250,000        2,500       27,500       --            --            30,000
  Net loss..............................      --           --           --          (72,321)       --           (72,321)
                                          ----------   -----------  ----------  ------------  -------------  ----------
Balance at December 31, 1992............   1,000,000       10,000       27,500      (72,321)       --           (34,821)
  Sale of Common Stock at $.60 per share
    in January 1993.....................      10,000          100        5,900       --            --             6,000
  Recapitalization resulting from
    election of C Corporation status....      --           --          (76,228)      76,228        --            --
  Sale of Series A Preferred Stock at
    $1.00 per share in March 1993.......      --           --          767,250       --            --           775,000
  Sale of Series B Preferred Stock at
    $1.70 in December 1993, net of
    offering costs......................      --           --        4,863,208       --            --         4,892,031
  Conversion of notes payable to Series
    B Preferred Stock at $1.70 per share
    in December 1993....................      --           --          248,529       --            --           250,000
  Exercise of stock options.............         937            9          198       --            --               207
  Net loss..............................      --           --           --       (1,004,677)       --        (1,004,677)
                                          ----------   -----------  ----------  ------------  -------------  ----------
Balance at December 31, 1993 (brought
  forward)..............................   1,010,937       10,109    5,836,357   (1,000,770)       --         4,883,740
</TABLE>
 
                                      F-5
<PAGE>
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
            STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (CONTINUED)
<TABLE>
<CAPTION>
                                            SERIES A PREFERRED          SERIES B              SERIES C
                                                  STOCK             PREFERRED STOCK        PREFERRED STOCK
                                          ----------------------  --------------------  ---------------------
                                           SHARES      AMOUNT      SHARES     AMOUNT     SHARES      AMOUNT
                                          ---------  -----------  ---------  ---------  ---------  ----------
<S>                                       <C>        <C>          <C>        <C>        <C>        <C>
Balance at December 31, 1993 (carried
  forward)..............................    775,000   $   7,750   3,029,412  $  30,294     --      $   --
  Exercise of stock options.............     --          --          --         --         --          --
  Net loss..............................     --          --          --         --         --          --
                                          ---------  -----------  ---------  ---------  ---------  ----------
Balance at December 31, 1994............    775,000       7,750   3,029,412     30,294     --          --
  Sale of Series B Preferred Stock at
    $1.70 per share in January and March
    1995, net of offering costs.........     --          --       3,653,094     36,531     --          --
  Value of warrants granted in
    connection with lease agreement.....     --          --          --         --         --          --
  Exercise of stock options.............     --          --          --         --         --          --
  Net loss..............................     --          --          --         --         --          --
                                          ---------  -----------  ---------  ---------  ---------  ----------
Balance at December 31, 1995............    775,000       7,750   6,682,506     66,825     --          --
  Sale of Series C Preferred Stock at
    $5.12 per share in April 1996, net
    of offering costs...................     --          --          --         --      1,953,700     19,537
  Value of warrants granted in
    connection with lease agreements....     --          --          --         --         --          --
  Exercise of stock options.............     --          --          --         --         --          --
  Deferred compensation related to stock
    options.............................     --          --          --         --         --          --
  Amortization of deferred
    compensation........................     --          --          --         --         --          --
  Net loss..............................     --          --          --         --         --          --
                                          ---------  -----------  ---------  ---------  ---------  ----------
Balance at December 31, 1996 (brought
  forward)..............................    775,000       7,750   6,682,506     66,825  1,953,700     19,537
 
<CAPTION>
                                                                                  DEFICIT
                                                                                ACCUMULATED
                                                COMMON STOCK        ADDITIONAL   DURING THE
                                          ------------------------   PAID-IN    DEVELOPMENT     DEFERRED
                                            SHARES       AMOUNT      CAPITAL       STAGE      COMPENSATION     TOTAL
                                          ----------   -----------  ----------  ------------  -------------  ----------
<S>                                       <C>          <C>          <C>         <C>           <C>            <C>
Balance at December 31, 1993 (carried
  forward)..............................   1,010,937    $  10,109   $5,836,357   $(1,000,770)  $   --        $4,883,740
  Exercise of stock options.............       3,750           38          787       --            --               825
  Net loss..............................      --           --           --       (4,408,231)       --        (4,408,231)
                                          ----------   -----------  ----------  ------------  -------------  ----------
Balance at December 31, 1994............   1,014,687       10,147    5,837,144   (5,409,001)       --           476,334
  Sale of Series B Preferred Stock at
    $1.70 per share in January and March
    1995, net of offering costs.........      --           --        6,116,721       --            --         6,153,252
  Value of warrants granted in
    connection with lease agreement.....      --           --           15,846       --            --            15,846
  Exercise of stock options.............      13,876          139        4,129       --            --             4,268
  Net loss..............................      --           --           --       (4,733,736)       --        (4,733,736)
                                          ----------   -----------  ----------  ------------  -------------  ----------
Balance at December 31, 1995............   1,028,563       10,286   11,973,840  (10,142,737)       --         1,915,964
  Sale of Series C Preferred Stock at
    $5.12 per share in April 1996, net
    of offering costs...................      --           --        9,972,008       --            --         9,991,545
  Value of warrants granted in
    connection with lease agreements....      --           --            7,680       --            --             7,680
  Exercise of stock options.............      24,865          248        6,151       --            --             6,399
  Deferred compensation related to stock
    options.............................      --           --        1,484,680       --         (1,484,680)      --
  Amortization of deferred
    compensation........................      --           --           --           --            773,271      773,271
  Net loss..............................      --           --           --       (6,480,601)       --        (6,480,601)
                                          ----------   -----------  ----------  ------------  -------------  ----------
Balance at December 31, 1996 (brought
  forward)..............................   1,053,428       10,534   23,444,359  (16,623,338)      (711,409)   6,214,258
</TABLE>
 
                                      F-6
<PAGE>
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
            STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY (CONTINUED)
   
<TABLE>
<CAPTION>
                                            SERIES A PREFERRED          SERIES B              SERIES C
                                                  STOCK             PREFERRED STOCK        PREFERRED STOCK
                                          ----------------------  --------------------  ---------------------
                                           SHARES      AMOUNT      SHARES     AMOUNT     SHARES      AMOUNT
                                          ---------  -----------  ---------  ---------  ---------  ----------
<S>                                       <C>        <C>          <C>        <C>        <C>        <C>
Balance at December 31, 1996 (carried
  forward)..............................    775,000   $   7,750   6,682,506  $  66,825  1,953,700  $  19,537
  Initial public offering at $9.00 per
    share in March 1997, net of offering
    costs...............................     --          --          --         --         --          --
  Conversion of Preferred Stock to
    Common Stock........................   (775,000)     (7,750)  (6,682,506)   (66,825) (1,953,700)   (19,537)
  Exercise of stock options.............     --          --          --         --         --          --
  Amortization of deferred
    compensation........................     --          --          --         --         --          --
  Net loss..............................     --          --          --         --         --          --
                                          ---------  -----------  ---------  ---------  ---------  ----------
Balance at September 30, 1997
  (unaudited)...........................     --       $  --          --      $  --         --      $   --
                                          ---------  -----------  ---------  ---------  ---------  ----------
                                          ---------  -----------  ---------  ---------  ---------  ----------
 
<CAPTION>
                                                                                  DEFICIT
                                                                                ACCUMULATED
                                                COMMON STOCK        ADDITIONAL   DURING THE
                                          ------------------------   PAID-IN    DEVELOPMENT     DEFERRED
                                            SHARES       AMOUNT      CAPITAL       STAGE      COMPENSATION     TOTAL
                                          ----------   -----------  ----------  ------------  -------------  ----------
<S>                                       <C>          <C>          <C>         <C>           <C>            <C>
Balance at December 31, 1996 (carried
  forward)..............................   1,053,428    $  10,534   $23,444,359 ($16,623,338)  $  (711,409)  $6,214,258
  Initial public offering at $9.00 per
    share in March 1997, net of offering
    costs...............................   3,000,000       30,000   24,604,261       --            --        24,634,261
  Conversion of Preferred Stock to
    Common Stock........................   4,705,602       47,057       47,055       --            --            --
  Exercise of stock options.............     139,071        1,389       36,163       --            --            37,552
  Amortization of deferred
    compensation........................      --           --           --           --            302,697      302,697
  Net loss..............................      --           --           --       (6,130,807)       --        (6,130,807)
                                          ----------   -----------  ----------  ------------  -------------  ----------
Balance at September 30, 1997
  (unaudited)...........................   8,898,047    $  88,980   $48,131,838 ($22,754,145)  $  (408,712)  $25,057,961
                                          ----------   -----------  ----------  ------------  -------------  ----------
                                          ----------   -----------  ----------  ------------  -------------  ----------
</TABLE>
    
 
                            See accompanying notes.
 
                                      F-7
<PAGE>
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
 
                            STATEMENTS OF CASH FLOWS
 
<TABLE>
<CAPTION>
                                                                                                        PERIOD FROM
                                                                                                       MAY 21, 1992
                                                                                NINE MONTHS ENDED       (INCEPTION)
                                              YEAR ENDED DECEMBER 31,             SEPTEMBER 30,             TO
                                         ----------------------------------  ------------------------  SEPTEMBER 30,
                                            1994        1995        1996        1996         1997          1997
                                         ----------  ----------  ----------  -----------  -----------  -------------
                                                                             (UNAUDITED)  (UNAUDITED)   (UNAUDITED)
<S>                                      <C>         <C>         <C>         <C>          <C>          <C>
OPERATING ACTIVITIES
Net loss...............................  $(4,408,231) $(4,733,736) $(6,480,601) $(4,182,669) $(6,130,807)  $(22,830,376)
Adjustments to reconcile net loss to
  net cash used in operating
  activities:
      Depreciation and amortization....     128,741     242,684     291,712      195,581      339,145     1,034,506
      Amortization of deferred
        compensation...................      --          --         773,271      --           302,697     1,075,968
      Value of warrants granted in
        connection with lease
        agreements.....................      --          15,846       7,680      --           --             23,526
      Loss on disposal of equipment....       8,689      --             784          784        1,726        11,199
      Changes in operating assets and
        liabilities:
        Inventories....................      --          --          --          --           (88,613)      (88,613)
        Prepaid expenses and other
          assets.......................     (22,176)    (90,927)    (37,517)     (22,879)    (157,894)     (314,657)
        Accounts payable...............     432,013    (232,539)     32,095      108,864      332,642       598,498
        Accrued salaries and
          expenses.....................      25,150      36,438      87,181       (3,578)     209,477       374,243
                                         ----------  ----------  ----------  -----------  -----------  -------------
Net cash used in operating
  activities...........................  (3,835,814) (4,762,234) (5,325,395)  (3,903,897)  (5,191,627)  (20,115,706)
INVESTING ACTIVITIES
Purchases of short-term investments....      --          --          --          --       (26,898,144)  (26,898,144)
Maturities of short-term investments...      --          --          --          --         7,745,000     7,745,000
Purchases of furniture and equipment...    (593,611)   (146,286)   (553,816)    (122,853)    (224,425)   (1,231,882)
Patent expenditures....................     (22,306)    (28,553)    (12,634)      (4,519)      (3,479)      (86,982)
Proceeds from sale of equipment........       3,612      --          --          --             1,958         5,570
                                         ----------  ----------  ----------  -----------  -----------  -------------
Net cash used in investing
  activities...........................    (612,305)   (174,839)   (566,450)    (127,372) (19,379,090)  (20,466,438)
 
FINANCING ACTIVITIES
Proceeds from notes payable............      --         504,629     409,125      --           --            706,974
Principal payments on notes payable and
  capital lease obligations............     (17,321)   (166,241)   (221,522)    (153,918)    (287,156)     (692,241)
Proceeds from (offering costs related
  to) issuance of common stock.........         825       4,268       6,403        4,813   24,671,812    24,718,558
Proceeds from issuance of preferred
  stock................................      --       6,153,252   9,991,542    9,991,542      --         21,820,283
                                         ----------  ----------  ----------  -----------  -----------  -------------
Net cash (used in) provided by
  financing activities.................     (16,496)  6,495,908  10,185,548    9,842,437   24,384,656    46,553,574
                                         ----------  ----------  ----------  -----------  -----------  -------------
(Decrease) increase in cash and cash
  equivalents..........................  (4,464,615)  1,558,835   4,293,703    5,811,168     (186,061)    5,971,430
Cash and cash equivalents at beginning
  of period............................   4,769,568     304,953   1,863,788    1,863,788    6,157,491       --
                                         ----------  ----------  ----------  -----------  -----------  -------------
Cash and cash equivalents at end of
  period...............................  $  304,953  $1,863,788  $6,157,491  $ 7,674,956  $ 5,971,430   $ 5,971,430
                                         ----------  ----------  ----------  -----------  -----------  -------------
                                         ----------  ----------  ----------  -----------  -----------  -------------
 
SUPPLEMENTAL DISCLOSURE OF NON-CASH
  INVESTING AND FINANCING ACTIVITIES
Purchase of equipment through capital
  lease obligations....................  $   47,655  $   --      $  409,125  $   --       $   612,128   $ 1,068,907
                                         ----------  ----------  ----------  -----------  -----------  -------------
                                         ----------  ----------  ----------  -----------  -----------  -------------
Conversion of note payable for Series B
  Preferred Stock......................  $  250,000  $   --      $   --      $   --       $   --        $   --
                                         ----------  ----------  ----------  -----------  -----------  -------------
                                         ----------  ----------  ----------  -----------  -----------  -------------
</TABLE>
 
                            See accompanying notes.
 
                                      F-8
<PAGE>
   
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
    
 
   
                         NOTES TO FINANCIAL STATEMENTS
    
 
   
             (UNAUDITED WITH RESPECT TO SEPTEMBER 30, 1997 AND THE
             NINE-MONTH PERIODS ENDED SEPTEMBER 30, 1996 AND 1997)
    
 
   
1.  DESCRIPTION OF BUSINESS
    
 
   
    Endocardial Solutions, Inc. (the "Company") designs, develops and
manufactures a minimally invasive and integrated diagnostic system that locates
and facilitates treatment of cardiac tachyarrhythmias. Tachyarrhythmias are
abnormal heart rhythms caused by disorders interfering with the normal
electrical activity of the heart, which, if undetected and untreated, can cause
palpitations, dizziness and fainting, or sudden cardiac death. The Company is
developing products to diagnose ventricular tachycardia, a widespread, complex
and serious form of tachyarrhythmia, and intends to utilize its technology to
produce products to diagnose atrial arrhythmias, including atrial fibrillation.
The Company believes that its proprietary technology will enable physicians to
rapidly and accurately map the heart's electric activity and locate the abnormal
heart rhythms through three-dimensional imaging.
    
 
   
2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
    
 
   
    CASH AND CASH EQUIVALENTS
    
 
   
    The Company considers all highly liquid investments with a maturity of three
months or less when purchased to be cash equivalents. At December 31, 1996, the
Company's investments in government securities approximated market value, with
no resulting unrealized gains and losses recognized.
    
 
   
    FURNITURE AND EQUIPMENT
    
 
   
    Furniture and equipment are recorded at cost. Depreciation is provided using
the straight-line method over the estimated useful lives of the assets ranging
from 3 to 7 years.
    
 
   
    PATENTS
    
 
   
    Patent costs are being amortized on a straight-line basis over five years.
The Company periodically reviews its patents for impairment in value. Any
adjustment from the analysis is charged to operations.
    
 
   
    INCOME TAXES
    
 
   
    Income taxes are accounted for under the liability method. Deferred income
taxes are provided for temporary differences between financial reporting and tax
bases of assets and liabilities.
    
 
   
    USE OF ESTIMATES
    
 
   
    The preparation of financial statements in conformity with generally
accepted accounting principles requires management to make estimates and
assumptions that affect the amounts reported in the financial statements and
accompanying notes. Actual results could differ from those estimates.
    
 
   
    STOCK-BASED COMPENSATION
    
 
   
    The Company follows Accounting Principles Board Opinion No. 25, ACCOUNTING
FOR STOCK ISSUED TO EMPLOYEES ("APB 25"), and related interpretations in
accounting for its stock options. Under APB 25, when the exercise price of stock
options equals the market price of the underlying stock on the date of grant, no
compensation expense is recognized.
    
 
                                      F-9
<PAGE>
   
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
    
 
   
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
    
 
   
             (UNAUDITED WITH RESPECT TO SEPTEMBER 30, 1997 AND THE
             NINE-MONTH PERIODS ENDED SEPTEMBER 30, 1996 AND 1997)
    
 
   
2.  SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (CONTINUED)
    
   
    In October 1995, the Financial Accounting Standards Board issued Statement
of Financial Accounting Standards No. 123, ACCOUNTING FOR STOCK-BASED
COMPENSATION ("Statement 123"). The Company adopted the disclosure only
provisions of Statement 123. Accordingly, the Company has made pro forma
disclosures of what net loss and loss per share would have been had the
provisions of Statement 123 been applied to the Company's stock options.
    
 
   
    IMPAIRMENT OF LONG-LIVED ASSETS
    
 
   
    The Company will record impairment losses on long-lived assets used in
operations when indicators of impairment are present and the undiscounted cash
flows estimated to be generated by those assets are less than the assets'
carrying amount.
    
 
   
    NET LOSS PER SHARE
    
 
   
    Net loss per share is computed using the weighted average number of shares
of common stock outstanding during the periods presented. Pursuant to Securities
and Exchange Commission Staff Accounting Bulletin No. 83 ("SAB No. 83"), shares
convertible into common stock issued by the Company at prices less than the
initial offering price during the 12 months immediately preceding the initial
public offering, plus stock options and warrants granted at exercise prices less
than the initial public offering price during the same period, have been
included in the determination of shares used in calculating the net loss per
share, using the treasury method, as if they were outstanding for all periods
presented.
    
 
   
    In February 1997, the Financial Accounting Standards Board ("FASB") issued
FASB Statement No. 128, "EARNINGS PER SHARE" ("Statement"). This Statement
replaces the presentation of primary earnings per share ("EPS") with basic EPS
and also requires dual presentation of basic and diluted EPS for entities with
complex capital structures. This Statement is effective for financial statements
for periods ending after December 15, 1997. For the nine months ended September
30, 1997, there is no difference between basic loss per share under Statement
No. 128 and loss per share as reported.
    
 
   
    INTERIM FINANCIAL INFORMATION
    
 
   
    The accompanying financial statements as of September 30, 1997 and for the
nine-month periods ended September 30, 1996 and 1997 are unaudited. In the
opinion of the management of the Company, these financial statements reflect all
adjustments, consisting only of normal and recurring adjustments necessary for a
fair presentation of the consolidated financial statements. The results of
operations for the nine-month period ended September 30, 1997 are not
necessarily indicative of the results that may be expected for the full year
ending December 31, 1997.
    
 
   
3.  INITIAL PUBLIC OFFERING
    
 
   
    On March 24, 1997, the Company received net proceeds of $18,832,500 from an
initial public offering of 2,250,000 shares of its common stock and $6,277,500
from a concurrent private placement of 750,000 shares of its common stock at
$9.00 per share. Also on March 24, 1997, all outstanding shares of the
    
 
                                      F-10
<PAGE>
   
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
    
 
   
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
    
 
   
             (UNAUDITED WITH RESPECT TO SEPTEMBER 30, 1997 AND THE
             NINE-MONTH PERIODS ENDED SEPTEMBER 30, 1996 AND 1997)
    
 
   
3.  INITIAL PUBLIC OFFERING (CONTINUED)
    
   
Company's preferred stock were automatically converted into an aggregate of
4,705,602 shares of common stock following the 1-for-2 reverse stock split.
    
 
   
4.  LONG-TERM DEBT AND CAPITAL LEASE OBLIGATIONS
    
 
   
    During January 1995, the Company executed a two-year and a three-year loan
agreement for approximately $245,000 and $259,000, respectively. The two-year
and three-year loan agreements accrue interest at 11.5% and 10.5% per annum,
respectively, and are payable in monthly installments of $11,377 and $8,358
including interest, respectively. The total amount payable under the loan
agreements as of December 31, 1995 and 1996 was approximately $368,000 and
$160,000, respectively.
    
 
   
    In October 1996, the Company entered into an equipment lease agreement with
a venture leasing company which provides lease financing of up to $1.0 million
under a lease line of credit for the acquisition of furniture, fixtures and
research and development equipment. As of December 31, 1996, the Company used
$409,000 of the line of credit which is included under capital lease obligations
on the Company's balance sheets. The line of credit expires on July 15, 1997,
and as of December 31, 1996, there remained $591,000 available under this
agreement.
    
 
   
    The Company leases certain research and development equipment under leases
which are accounted for as capital leases for financial statement purposes. The
cost of furniture and equipment in the accompanying balance sheets includes the
following amounts under capital leases:
    
 
   
<TABLE>
<CAPTION>
                                                                             DECEMBER 31,
                                                                         ---------------------
                                                                           1995        1996
                                                                         ---------  ----------
<S>                                                                      <C>        <C>
Research and development equipment.....................................  $  47,655  $  456,780
Less accumulated amortization..........................................     22,700      69,096
Net assets under capital leases........................................  $  24,955  $  387,684
</TABLE>
    
 
   
    Future minimum lease payments under capital leases and principal maturities
of long-term debt consisted of approximately the following as of December 31,
1996:
    
 
   
<TABLE>
<CAPTION>
                                                            CAPITAL     LONG-TERM
                                                             LEASES       DEBT        TOTAL
                                                           ----------  -----------  ----------
<S>                                                        <C>         <C>          <C>
Year ending December 31:
  1997...................................................  $  154,699   $ 122,091   $  276,790
  1998...................................................     154,699      38,378      193,077
  1999...................................................     136,434      --          136,434
                                                           ----------  -----------  ----------
Total minimum payments...................................     445,832     160,469      606,301
Less amount representing interest........................      51,055      --           51,055
                                                           ----------  -----------  ----------
Present value of net minimum payments....................     394,777     160,469      555,246
Less current portion.....................................     130,864     122,091      252,955
                                                           ----------  -----------  ----------
Long-term obligations, net of current portion............  $  263,913   $  38,378   $  302,291
                                                           ----------  -----------  ----------
                                                           ----------  -----------  ----------
</TABLE>
    
 
                                      F-11
<PAGE>
   
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
    
 
   
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
    
 
   
             (UNAUDITED WITH RESPECT TO SEPTEMBER 30, 1997 AND THE
             NINE-MONTH PERIODS ENDED SEPTEMBER 30, 1996 AND 1997)
    
 
   
4.  LONG-TERM DEBT AND CAPITAL LEASE OBLIGATIONS (CONTINUED)
    
   
    Interest paid for the years ended December 31, 1994, 1995 and 1996 was
$6,132, $82,993 and $64,691, respectively.
    
 
   
5.  OPERATING LEASES
    
 
   
    The Company leases its office facility and certain equipment under operating
lease agreements which expire on various dates through 1999. Under the office
facility agreement, the Company is required to pay a base rent plus certain
operating expenses. Rent expense was $87,152, $275,311 and $178,419 for the
years ended December 31, 1994, 1995 and 1996, respectively.
    
 
   
    Future minimum lease commitments required under non-cancelable operating
leases with remaining terms in excess of one year as of December 31, 1996 are as
follows:
    
 
   
<TABLE>
<S>                                                                 <C>
Year ending December 31:
  1997............................................................  $ 477,027
  1998............................................................    356,578
  1999............................................................     53,949
                                                                    ---------
                                                                    $ 887,554
                                                                    ---------
                                                                    ---------
</TABLE>
    
 
   
6.  PREFERRED STOCK
    
 
   
    On March 26, 1993, the Company issued 775,000 shares of Series A Preferred
Stock to investors at $1.00 per share. On December 22, 1993, the Company issued
2,882,354 shares of Series B Preferred Stock to investors at $1.70 per share. On
January 31, 1995 and on March 7, 1995, the Company issued 3,588,388 and 64,706
shares of Series B Preferred Stock, respectively, to investors at $1.70 per
share. The Series A and Series B Preferred Stock have certain voting and
registration rights, are convertible into common stock on a one-for-one basis
and have preference over common stock upon liquidation.
    
 
   
    On October 29, 1993 and on November 29, 1993, the Company borrowed $125,000
on each date from certain Series A Preferred stockholders. The notes earned
interest at 7% and were either payable January 15, 1994 or convertible into
Series B Preferred Stock at a price equal to the price paid per share by
investors purchasing Series B Preferred Stock. The notes were converted into
147,058 shares of Preferred Stock on December 23, 1993.
    
 
   
    On April 24, 1996, the Company issued 1,953,700 shares of Series C Preferred
Stock to investors at $5.12 per share from which the Company received net
proceeds of $9,992,000. The Series C Preferred Stock has certain voting and
registration rights, is convertible into common stock on a one-for-one basis and
has preference over common stock upon liquidation.
    
 
   
7.  REVERSE STOCK SPLIT
    
 
   
    Subsequent to December 31, 1996, the Board of Directors approved a reverse
stock split of 1-for-2 for the Company's common stock and preferred stock.
Accordingly, all share, per share, weighted average share, and stock option
information has been restated to reflect the split. The reverse stock split will
have
    
 
                                      F-12
<PAGE>
   
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
    
 
   
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
    
 
   
             (UNAUDITED WITH RESPECT TO SEPTEMBER 30, 1997 AND THE
             NINE-MONTH PERIODS ENDED SEPTEMBER 30, 1996 AND 1997)
    
 
   
7.  REVERSE STOCK SPLIT (CONTINUED)
    
   
no effect upon the numbers of shares of preferred stock issued and outstanding
(as opposed to the conversion prices of the preferred stock and the numbers of
shares of common stock into which the preferred stock will convert).
Accordingly, all preferred stock and preferred stock price amounts have not been
adjusted for the reverse stock split. In addition, the Board of Directors
approved an increase in the authorized shares of capital stock to 50,000,000,
including 40,000,000 shares of common stock and 10,000,000 shares of
undesignated preferred stock.
    
 
   
8.  STOCK OPTIONS AND WARRANTS
    
 
   
    The Company has a stock option plan to provide incentives to employees and
consultants. The options can either be incentive stock options (ISO) or
nonstatutory stock options (NSO). Options granted under the plan are at prices
not less than fair market value on the date of the grant. The plan authorizes
the issuance of options to officers, other key employees and advisors. The
following table summarizes activity under the plan:
    
 
   
<TABLE>
<CAPTION>
                                                                                   PLAN OPTIONS         WEIGHTED
                                                                     SHARES        OUTSTANDING           AVERAGE
                                                                   AVAILABLE   --------------------  EXERCISE PRICE
                                                                   FOR GRANT      NSO        ISO        PER SHARE
                                                                   ----------  ---------  ---------  ---------------
<S>                                                                <C>         <C>        <C>        <C>
Balance at December 31, 1993.....................................     243,000     24,063    104,500     $     .20
  Additional shares reserved for issuance........................     375,000     --         --            --
  Granted........................................................    (290,000)    27,500    262,500           .34
  Canceled.......................................................      20,000     --        (20,000)          .34
  Exercised......................................................      --         (3,750)    --               .22
                                                                   ----------  ---------  ---------
Balance at December 31, 1994.....................................     348,000     47,813    347,000           .29
  Granted........................................................    (301,500)    33,500    268,000           .34
  Canceled.......................................................      47,062     --        (47,062)          .33
  Exercised......................................................      --         --        (13,876)          .31
                                                                   ----------  ---------  ---------
Balance at December 31, 1995.....................................      93,562     81,313    554,062           .32
  Additional shares reserved for issuance........................     350,000     --         --            --
  Granted........................................................    (298,750)     6,250    292,500          2.80
  Canceled.......................................................      11,478     --        (11,478)          .33
  Exercised......................................................      --        (10,313)   (14,552)          .26
                                                                   ----------  ---------  ---------
Balance at December 31, 1996.....................................     156,290     77,250    820,532     $    1.14
                                                                   ----------  ---------  ---------
                                                                   ----------  ---------  ---------
</TABLE>
    
 
                                      F-13
<PAGE>
   
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
    
 
   
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
    
 
   
             (UNAUDITED WITH RESPECT TO SEPTEMBER 30, 1997 AND THE
             NINE-MONTH PERIODS ENDED SEPTEMBER 30, 1996 AND 1997)
    
 
   
8.  STOCK OPTIONS AND WARRANTS (CONTINUED)
    
   
    The following table summarizes information about the stock options
outstanding at December 31, 1996:
    
 
   
<TABLE>
<CAPTION>
                              PLAN OPTIONS OUTSTANDING           OPTIONS EXERCISABLE
                        -------------------------------------  ------------------------
                                      WEIGHTED-    WEIGHTED-                 WEIGHTED-
                                       AVERAGE      AVERAGE                   AVERAGE
                                      REMAINING    EXERCISE                  EXERCISE
  RANGE OF EXERCISE       NUMBER     CONTRACTUAL   PRICE PER     NUMBER      PRICE PER
        PRICES          OUTSTANDING     LIFE         SHARE     EXERCISABLE     SHARE
- ----------------------  -----------  -----------  -----------  -----------  -----------
<S>                     <C>          <C>          <C>          <C>          <C>
     $ .20 - $.34          601,532      7 years    $     .32      362,384    $     .29
         .60                24,750      7 years          .60        5,500          .60
         2.40              168,000      9 years         2.40        4,021         2.40
         3.70               79,000      9 years         3.70        3,750         3.70
         5.00               24,000     10 years         5.00       --           --
                        -----------                            -----------
    $ .20 - $5.00          897,782    7.5 years    $    1.14      375,655    $     .36
                        -----------                            -----------
                        -----------                            -----------
</TABLE>
    
 
   
    Options outstanding under the plan expire at various dates during the period
from April 2003 through December 2006. Exercise prices for options outstanding
as of December 31, 1996 ranged from $.20 to $5.00 per share. The number of
options exercisable as of December 31, 1994, 1995 and 1996 were 107,708, 223,993
and 375,655, respectively, at weighted average exercise prices of $.26, $.29 and
$.36 per share, respectively.
    
 
   
    The weighted-average grant date fair value of options granted during the
years ended December 31, 1995 and 1996 was $3.12 and $5.58 per share,
respectively.
    
 
   
    In November 1994, the Company entered into a three year operating lease
agreement for research and development equipment. In connection with the
agreement, the Company granted the lessor a warrant to purchase 93,213 shares of
Series B Preferred Stock at $1.70 per share. The warrant expires five years from
the grant date and was deemed to have a value of $15,846. Such value was
expensed during the year ended December 31, 1995.
    
 
   
    In October 1996, the Company entered into an equipment lease agreement for
research and development equipment. In connection with the agreement, the
Company granted the venture leasing company a warrant to purchase 15,000 shares
of the Company's Series D Preferred Stock at a purchase price of $5.12 per
share. The warrant expires five years from the grant date and was deemed to have
a value of $7,680. Such value was expensed during the year ended December 31,
1996.
    
 
   
    The Company has elected to follow Accounting Principles Board Opinion No.
25, ACCOUNTING FOR STOCK ISSUED TO EMPLOYEES ("APB 25") and related
Interpretations in accounting for its employee stock options because, as
discussed below, the alternative fair value accounting provided for under FASB
Statement No. 123, ACCOUNTING FOR STOCK-BASED COMPENSATION ("Statement 123"),
requires use of option valuation models that were not developed for use in
valuing employee stock options. Under APB 25, because the exercise price of the
Company's employee stock options equals the market price of the underlying stock
on the date of grant, no compensation expense is recognized.
    
 
                                      F-14
<PAGE>
   
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
    
 
   
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
    
 
   
             (UNAUDITED WITH RESPECT TO SEPTEMBER 30, 1997 AND THE
             NINE-MONTH PERIODS ENDED SEPTEMBER 30, 1996 AND 1997)
    
 
   
8.  STOCK OPTIONS AND WARRANTS (CONTINUED)
    
 
   
    Pro forma information regarding net loss and loss per share is required by
Statement 123, and has been determined as if the Company had accounted for its
employee stock options under the fair value method of Statement 123. The fair
value for these options was estimated at the date of grant using a minimum value
option pricing model with the following weighted-average assumptions for 1996
and 1995, respectively: risk-free interest rates ranging from 5.0% to 6.2% and a
weighted-average expected life of the option of 4 years.
    
 
   
    The Black-Scholes option valuation model was developed for use in estimating
the fair value of traded options which have no vesting restrictions and are
fully transferable. In addition, option valuation models require the input of
highly subjective assumptions. Because the Company's employee stock options have
characteristics significantly different from those of traded options, and
because changes in the subjective input assumptions can materially affect the
fair value estimate, in management's opinion, the existing models do not
necessarily provide a reliable single measure of the fair value of its employee
stock options.
    
 
   
    For purposes of pro forma disclosures, the estimated fair value of the
options is amortized to expense over the options' vesting period. The Company's
pro forma information is as follows:
    
 
   
<TABLE>
<CAPTION>
                                                                      1995           1996
                                                                  -------------  -------------
<S>                                                               <C>            <C>
Pro forma net loss..............................................  $  (4,841,089) $  (6,836,294)
Pro forma net loss per common share.............................  $       (3.40) $       (4.78)
</TABLE>
    
 
   
    The pro forma effect on net loss for 1995 and 1996 is not representative of
the pro forma effect on net loss in future years because it does not take into
consideration expense related to grants made prior to 1995.
    
 
   
9.  DEFERRED COMPENSATION
    
 
   
    For options granted during the year ended December 31, 1996 to purchase a
total of 298,750 shares of common stock at exercise prices ranging from $.34 to
$5.00 per share, the Company recognized $1,484,680 as deferred compensation for
the excess of the deemed value for accounting purposes of the common stock
issuable upon exercise of such options over the aggregate exercise price of such
options. The deferred compensation expense is amortized ratably over the vesting
period of the options. For the year ended December 31, 1996, $773,271 was
expensed.
    
 
   
    The remaining unamortized deferred compensation is expected to be charged to
operations as follows:
    
 
   
<TABLE>
<S>                                                                 <C>
1997..............................................................  $ 402,101
1998..............................................................    216,516
1999..............................................................     92,792
                                                                    ---------
                                                                    $ 711,409
                                                                    ---------
                                                                    ---------
</TABLE>
    
 
                                      F-15
<PAGE>
   
                          ENDOCARDIAL SOLUTIONS, INC.
                         (A DEVELOPMENT STAGE COMPANY)
    
 
   
                   NOTES TO FINANCIAL STATEMENTS (CONTINUED)
    
 
   
             (UNAUDITED WITH RESPECT TO SEPTEMBER 30, 1997 AND THE
             NINE-MONTH PERIODS ENDED SEPTEMBER 30, 1996 AND 1997)
    
 
   
10.  INCOME TAXES
    
 
   
    At December 31, 1996, the Company had net operating loss carryforwards of
approximately $15,850,000. The net operating loss carryforwards are available to
offset future taxable income and begin to expire in the year 2007. No benefit
has been recorded for such loss carryforwards, and utilization in future years
may be limited under Section 382 of the Internal Revenue Code if significant
ownership changes have occurred.
    
 
   
    Components of deferred tax assets are as follows:
    
 
   
<TABLE>
<CAPTION>
                                                                          DECEMBER 31,
                                                                  ----------------------------
                                                                      1995           1996
                                                                  -------------  -------------
<S>                                                               <C>            <C>
Net operating loss carryforwards................................  $   4,054,000  $   6,340,000
Less valuation allowance........................................     (4,054,000)    (6,340,000)
                                                                  -------------  -------------
Deferred tax asset..............................................  $    --        $    --
                                                                  -------------  -------------
                                                                  -------------  -------------
</TABLE>
    
 
   
11.  RELATED PARTY TRANSACTION
    
 
   
    The Company paid approximately $694,000, $475,000 and $59,000 for the years
ended December 31, 1994, 1995 and 1996, respectively, to Novel Biomedical in
connection with research and development performed for the Company. The owner of
Novel Biomedical is a founder and stockholder of the Company.
    
 
   
12.  SOURCES OF SUPPLY
    
 
   
    The Company purchases raw materials and certain key components of its
products, including the computer workstation and certain components for its
catheter from sole, single or limited source suppliers. The Company currently
has no agreements that would assure delivery of raw materials and components
from such suppliers. Establishing additional or replacement suppliers for any of
the numerous components used in the Company's products, if required, may not be
accomplished quickly and could involve significant additional costs. The
inability of any of the Company's suppliers to provide an adequate supply of
components in a timely manner, or the inability of the Company to locate
qualified alternative suppliers for material and components at reasonable costs,
could adversely affect the Company's business, financial condition and results
of operations.
    
 
                                      F-16
<PAGE>
No dealer, salesperson or other person is authorized to give any information or
to make representations not contained in this Prospectus in connection with the
offer made by this Prospectus and, if given or made, such information or
representations must not be relied upon as having been authorized by the
Company, the Selling Stockholder or any other person. This Prospectus does not
constitute an offer to sell or a solicitation of an offer to buy any of the
securities offered hereby by anyone in any jurisdiction in which such offer or
solicitation is not authorized or in which the person making such offer or
solicitation is not qualified to do so or to anyone to whom it is unlawful to
make such an offer or solicitation. Neither the delivery of this Prospectus nor
any sale made hereunder shall, under any circumstances, create any implication
that the affairs of the Company since the date hereof or the information herein
is correct as of any time subsequent to the date of this Prospectus.
 
                            ------------------------
 
                               TABLE OF CONTENTS
 
   
<TABLE>
<CAPTION>
                                                                            Page
                                                                            ----
<S>                                                                         <C>
Prospectus Summary........................................................    3
Risk Factors..............................................................    4
Use of Proceeds...........................................................   13
Selling Stockholder.......................................................   14
Plan of Distribution......................................................   14
Price Range of Common Stock...............................................   15
Dividend Policy...........................................................   15
Selected Financial Data...................................................   16
Management's Discussion and Analysis of Financial Condition and Results of
 Operations...............................................................   17
Business..................................................................   20
Management................................................................   35
Certain Transactions......................................................   42
Principal Stockholders....................................................   45
Description of Capital Stock..............................................   47
Shares Eligible for Future Sale...........................................   49
Validity of Shares........................................................   50
Experts...................................................................   50
Available Information.....................................................   50
Index to Financial Statements.............................................  F-1
</TABLE>
    
 
                                 750,000 SHARES
 
                                     [LOGO]
 
                                  COMMON STOCK
 
                               -----------------
                              P R O S P E C T U S
                               -----------------
 
   
                                January 9, 1998
    

<PAGE>
   
                                                                    EXHIBIT 23.1
    
 
   
                        CONSENT OF INDEPENDENT AUDITORS
    
 
   
    We consent to the reference to our firm under the caption "Experts" and to
the use of our report dated January 7, 1997, in the Registration Statement (Form
S-1) and the related Prospectus of Endocardial Solutions, Inc. for the
registration of 750,000 shares of its common stock.
    
 
   
                                          /s/ Ernst & Young LLP
    
 
   
Minneapolis, Minnesota
January 7, 1997
    


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