Document:

<PAGE>

                                                                   Exhibit 10.23

     AGREEMENT dated as of the 22nd day of July, 1993 by and between NITINOL
MEDICAL TECHNOLOGIES, INC., (hereinafter called "Employer") and STEPHEN J.
KLESHINSKI (hereinafter called "Executive").

                                  WITNESSETH
                                  ----------

     WHEREAS, Employer has developed and is developing medical devices,
including devices made of the shape memory metal alloy, nitinol, the first of
which is a patented vena cava filter;

     WHEREAS, Executive has been employed by Employer as director of research
and development and quality control and assurance, and Employer and Executive
desire to enter into an agreement to continue such employment;

     NOW, THEREFORE, in consideration of the premises and the mutual agreements
herein contained, the parties hereto hereby agree as follows:

     1.  Employment.  Employer hereby agrees to employ Executive, and Executive
         ----------
agrees to serve for the term of this Agreement on the terms and conditions
hereinafter set forth.

     2.  Term.  This Agreement shall be for a term of five (5) years commencing
         ----
June 1, 1993 and ending May 31, 1998. At the end of such term, or any additional
term, this Agreement shall automatically renew for an additional term of one
year on the same basis as that in effect at the end of any such term, unless one
party shall notify the other in writing, not later than three months prior to
the end of any term, that such party wishes to terminate employment at the end
of the then current term.

     3.  Extent of Services; Duties.  Executive will devote his full time and
         --------------------------
efforts to the business and affairs of the Employer and shall not, during the
term of this Agreement, be engaged in any other business activity. Executive
will work in the areas of research and development and quality control and
assurance, and will use his best efforts to promote the interests of Employer.
Executive will hold the office of Vice President, reporting to the Director of
Science and the President and such other person as directed by the President and
the Board of Directors of the Employer. Notwithstanding the foregoing, the
Executive shall not be precluded from devoting such time to his personal
financial affairs as shall not interfere with his duties hereunder, and shall be
entitled to holidays in accordance with the practice of Employer.

     4.  Compensation.  Employer will compensate Executive for all services
         ------------
rendered hereunder at a salary of $80,000 per annum from June 1, 1993 through
May 31, 1994; $87,000 per annum from June 1, 1994 through May 31, 1995; $94,000
per annum from June 1, 1995 through May 31, 1996; $100,000 per annum from June
1, 1996 through May 31, 1997 and $105,000 per annum from June 1, 1997 through
May 31, 1998.

     5.  Career Incentive Bonus Plan.  Executive was previously granted 30,000
         ---------------------------
Units under the Career Incentive Bonus Plan. Employer agrees to grant an
additional 120,000 Units under the Plan to Executive, effective as of July 1,
1993 in accordance with the
<PAGE>

terms of the plan. All Units shall convert to common stock of the Company as
provided in the Plan, and when as and if the Company ceases to be an
S corporation.

     6.  Expenses.  Employer shall reimburse Executive against appropriate
         --------
vouchers for authorized business expenses reasonably incurred by him in the
performance of his duties pursuant to the terms of this Agreement.

     7.  Secrecy; Inventions.
         -------------------

         (a)  Executive agrees that he shall not, during or after the
     termination of this Agreement, for any reason whatsoever, divulge, furnish
     or make accessible to any person, firm, corporation or other business
     entity, any confidential information, including but not limited to,
     inventions, processes, trade secrets, practices, methods, products or any
     confidential or secret aspect of the business of the Employer without the
     prior written consent of the Employer. This provision shall not apply to
     any confidential information which, through no breach of this agreement by
     Executive, becomes generally known in the medical device industry.

         (b)  Executive agrees to communicate and make known to the Employer in
     a preservable manner all significant knowledge acquired by him during the
     term of this Agreement, including laboratory notes and logs relating to any
     methods, developments, and/or improvements, or know-how which concern, or
     could concern the present or future business of the Employer.

         (c)  Executive agrees to assign to Employer any invention, idea,
     discovery or improvement conceived of, developed or perfected, solely or
     jointly, by Executive during the term of this Agreement or Executive's
     prior Agreement with Employer relating to medical devices or to the making,
     fabrication, training or use of nitinol, and to execute all documents and
     do all further acts which may be necessary or appropriate to perfect such
     assignment and at the request of Employer to cause a patent application to
     be made and a patent to issue and/or to defend a patent application or a
     patent on any such invention, in the United States and any other country,
     provided that all expenses in connection herewith shall be paid by
     Employer.

     8.  During the term of this Agreement and any renewal thereof, Employer
shall pay Executive a 1% royalty on the gross revenues resulting from the sale
of any product made and or sold in a jurisdiction where the Employer has a
patent, filed subsequent to the date of this agreement, on an invention of
Executive. Net Sales shall be the amount actually collected and shall not
include transportation charges. Royalties shall be paid to Executive quarterly
within 75 days after the end of each calendar quarter and Executive shall have
the right within one year after receipt of statement to have a public
accountant, during normal business hours, audit Employer's books to verify the
accuracy of the royalty payments due pursuant to this Section 8.

     9.  Restrictive Covenant.
         --------------------

         (a)  Executive agrees that during the term hereof and for a period of
     18 months next succeeding the termination of his employment with Employer
     for any reason whatsoever, he will not directly or indirectly engage in any
     business activity in competition with the business then being conducted or
     actively contemplated by Employer, whether for Executive's own account or
     as executive, partner, officer,

                                      -2-
<PAGE>

     director, consultant or holder of more than 5% equity interest in any other
     entity or person. Executive further agrees that during said 18 month period
     he will not hire, offer to hire, entice away or try to persuade any
     executive, employee, supplier or agent of Employer to discontinue the
     relationship with the Employer, or assist any member of his immediate
     family, any business associate or other person, for consideration or
     otherwise, to do any of the aforesaid prohibited things. During the course
     of said 18 month period, Executive shall advise Employer, in writing, if he
     has received and wishes to accept any offer of employment from such a
     competitor. Such writing shall be sufficiently detailed regarding the
     nature and scope of the position and compensation offered. The Employer
     shall then have thirty (30) days following the receipt of said written
     notification to advise Executive of its election:

              (i)  To waive the provision of this Section 8, only in which case
         Executive shall be free to accept such employment subject to all the
         other terms and conditions set forth herein; or

              (ii) To insist upon full compliance with the provisions of this
         Paragraph 9, in which case Employer shall compensate Executive at the
         base salary rate actually offered by its competitor for the duration of
         the aforesaid 18 month period or until Executive shall be employed
         elsewhere.

          (b)  If Executive shall breach any of this Section 9, all Career
     Incentive Bonus Plan benefits, whether vested or unvested, shall lapse
     until final resolution of any claims by Employer for money damages, and
     Employer, in addition to any money damages, shall be entitled to an
     injunction to be issued by a court of competent jurisdiction enjoining,
     restraining or restricting Executive from such breach or violation.

     10.  Miscellaneous.
          -------------

          (a)  Neither this Agreement nor its execution and delivery has been
     induced by any representation, stipulation, warranty, agreement or
     understanding of any kind other than those specifically set forth herein.
     This Agreement constitutes the whole agreement between the parties hereto
     and there are no terms other than those contained herein. No variation
     hereof shall be deemed valid unless in writing and signed by the parties
     hereto and no discharge of the terms hereof shall be deemed valid unless by
     full performance by the parties hereto or by a writing signed by the
     parties hereto. No waiver by either party of any breach of any provision or
     condition of this Agreement shall be deemed a waiver of a breach of a
     similar or dissimilar provision or condition at the same time or any prior
     or subsequent time or of the provision or condition itself.

          (b)  Each provision of this Agreement is intended to be severable and
     the invalidity or illegality of any portion of this Agreement shall not
     affect the validity or legality of the remainder hereof. If any of the
     provisions of this Agreement should be determined to be unenforceable by
     reason of being unreasonable in duration or in area, then such provision is
     intended to and shall extend only for such period of time and in such area
     as is determined to be reasonable and enforceable.

          (c)  This Agreement supersedes and replaces the Agreement between the
     parties dated June 1, 1991.

                                      -3-
<PAGE>

          (d)  All notices, requests, demands and other communications provided
     for by this Agreement shall be in writing and shall be deemed to have been
     given at the time mailed enclosed in a certified postage-paid envelope,
     return receipt requested, addressed to the addresses of the respective
     parties stated below or to such changed addresses as such parties may have
     fixed by a notice, and simultaneously by facsimile telephone to the Fax
     phone number provided by the parties; provided, however, that any notice of
     any change of address or change of Fax number shall be effective only upon
     receipt.

     If to the Employer:

     c/o C. Leonard Gordon
     461 Fifth Ave. 23rd Floor
     New York, NY 10017-6234
     Fax (212) 684-3043

     cc:  Jack Reinstein
          7779 Willow Glen Road
          Los Angeles, CA 90046-1610

     If to the Executive:

          599 Country Way
          Scituate, MA 02066

          (e)  This agreement shall inure to the benefit of and be binding upon
     the Employer, its successors and assigns, and upon the Executive, his
     heirs, executors, administrators and legal representatives.

          (f)  Captions contained in this Agreement are inserted only as a
     matter of convenience and for reference and in no way define, limit, extend
     or describe the scope of this Agreement or the intent of any provision
     hereof.

          (g)  The terms and provisions of this Agreement and any dispute or
     controversy arising hereunder shall be governed by the laws of the State of
     New York applicable to contracts made and to be performed therein, without
     giving effect to the principles of conflicts of laws thereof. Any dispute
     or controversy arising out of this Agreement shall be submitted to binding
     arbitration to be held in the City of New York in accordance with the rules
     of the American Arbitration Association then in effect.

          (h)  This Agreement may be executed in several counterparts and all so
     executed shall constitute one Agreement, binding on all parties hereto,
     notwithstanding that all the parties are not signatories to the original or
     the same counterpart.

                                      -4-
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have hereunder set their hands and
seals the day and year first above written.

                              NITINOL MEDICAL TECHNOLOGIES, INC.

                              By: /s/ C.  Leonard Gordon
                                  ------------------------------
                                  C. Leonard Gordon
                                  Chief Executive Officer

                              /s/ Stephen J. Kleshinski
                              -------------------------------------
                              Stephen J. Kleshinski

                                      -5-
<PAGE>

                            SUPPLEMENTAL AGREEMENT

     This Supplemental Agreement by and between NITINOL MEDICAL TECHNOLOGIES,
INC., (hereinafter referred to as "EMPLOYER") and STEPHEN J. KLESHINSKI
(hereinafter referred to as "EXECUTIVE") is effective as of the First day of
June, 1994.

     WHEREAS, EMPLOYER has entered into a License Development Agreement by and
between Boston Scientific Corporation and EMPLOYER dated as of the 1st day of
November, 1994 (The "License Agreement").

     1.  EMPLOYER and EXECUTIVE are parties to a prior Agreement dated as of the
22nd day of July, 1993 (the "Prior Agreement"), a copy of which is attached
hereto. The purpose of this Supplemental agreement is to amend the provisions of
paragraph 8 of the Prior Agreement; but the Prior Agreement shall otherwise
remain in full force and effect.

     2.  Paragraph 8 of the Prior Agreement is hereby amended to read as
follows:

         8.  (a)   During the term of this Agreement and any renewal thereof,
     EMPLOYER shall pay EXECUTIVE a royalty with respect to any product (other
     than a product including a Stent, as that term is defined in Section 1.20
     of the License Agreement, or a Vena Cava filter product) made, used or sold
     by EMPLOYER or any licensee of EMPLOYER in any jurisdiction EMPLOYER has an
     Executive Patent (as defined below) the claims of which cover such
     manufacture, use or sale.  With respect to any such product sold by
     EMPLOYER, the royalty shall be 1% of EMPLOYER's Net Sales (defined
     substantially as EMPLOYER'S gross sales adjusted as provided in the
     definition of Net Sales in Section 1.14 of the License Agreement, with such
     modifications as are appropriate to the circumstances) of such products;
     with respect to any such products sold (or to be sold) by a third party
     from which EMPLOYER directly or indirectly receives any payment with
     respect to any Executive Patent, the royalty shall be 5% of such payments.
     In the case of an Executive Patent in which EXECUTIVE is not the sole
     inventor, the royalty shall be apportioned (e.g., if the product is covered
     by only one Executive Patent as to which there are two inventors, EXECUTIVE
     shall receive a royalty equal to one-half the royalty which he would have
     received if he had been the sole inventor).  Notwithstanding the foregoing
     no royalty shall be paid to EXECUTIVE with respect to any such product if
     EMPLOYER establishes that no invention which is the subject of any
     Executive Patent contributed to the value of such product.

         (b)  EMPLOYER shall pay EXECUTIVE an amount equal to 5% of all
     licensing fees actually collected by EMPLOYER in conjunction with the sale
     or licensing of Stents or Products (as such terms are defined in Section
     1.18 and 1.20 of the License Agreement).  With respect to each Stent
     Product, such amount shall be due and payable for a period of ten (10)
     years following the first commercial sale of such product in any
     jurisdiction.  In the event that EMPLOYER collects any monies from a third
     party as designated as an advance against future license fees, such monies
     shall be considered to have been collected when fully vested in EMPLOYER.
<PAGE>

         (c)  The payments to EXECUTIVE provided in subparagraphs (a) and (b)
     above shall if such be reduced by 50% from and after the time when
     EXECUTIVE's employment with EMPLOYER is terminated by EXECUTIVE voluntarily
     (but not by reason of death, sickness or other disability) or by EMPLOYER
     with due cause, but otherwise shall not be reduced, provided, however, that
     if termination under such circumstances shall occur within three years of
     the date of this Agreement said payment shall terminate.

         (d) The payments to EXECUTIVE provided in subparagraphs (a) and (b)
     above shall be made as promptly as practicable, but in any event within 75
     days at the end of each calendar quarter with respect to payments received
     by the EMPLOYER during such calendar quarter; if no payments are due with
     respect to any calendar quarter, EMPLOYER shall provide EXECUTIVE a
     statement to such effect within the 75 day period.  EMPLOYER shall keep
     complete and accurate books and records from which the amounts of such
     payments may be ascertained, and within one year after receipt of any
     payment or statement.  EXECUTIVE, or a representative of EXECUTIVE, shall
     have the right to examine such books and records during business hours once
     in each calendar year to verify the accuracy of such payment or statement.

         (e) EMPLOYER's obligations under this Paragraph 8 may be assigned only
     in connection with the sale or other transfer of all or substantially all
     of EMPLOYER's business to which the subject matter of this paragraph
     relates, and then only if the assignee agrees to be bound thereby in a
     writing delivered to EXECUTIVE in advance of such transfer.

         (f)  As used in this Paragraph 8,

         "Executive Patent" means any patent issued, and any patent application
     filed, after the effective date of the Prior Agreement in which EXECUTIVE
     is a sole or joint inventor.

         "Stent" shall have the same meaning as nitinol Stent in the Agreement
     with Boston Scientific Corporation.

NITINOL MEDICAL TECHNOLOGIES, INC              STEPHEN J.  KLESHINSKI

By:  /s/ C. Leonard Gordon                     By: /s/ Stephen J. Kleshinski
     -------------------------------               -----------------------------
     C. Leonard Gordon
     Chief Executive Officer

Date: January 12, 1995                         Date: January 22, 1995
      ------------------------                       -----------------------

                                      -2-<PAGE>

                                                                   Exhibit 10.57
                          WAIVER AND CONSENT AGREEMENT
                          ----------------------------

     This is a Waiver and Consent Agreement dated as of March 20, 2000 by and
among Brown Brothers Harriman & Co. ("BBH"), J.H. Whitney & Co. ("JHW"), Whitney
Subordinated Debt Fund, L.P. ("WSDF" and, together with JHW, "Whitney") and the
Borrowers (as defined below) party hereto.

     Reference is made to (i) that certain Credit Agreement, dated as of
September 13, 1999 (the "U.S. Credit Agreement"), by and among NMT Medical, Inc.
("NMT") and its domestic subsidiaries (together with NMT, the "U.S. Borrowers")
and BBH, (ii) that certain Credit Agreement, dated as of September 13, 1999 (the
"French Credit Agreement"), by and among NMT NeuroSciences Implants (France) SA
and NMT NeuroSciences Instruments (France) SARL, each a wholly owned subsidiary
of NMT (collectively, the "French Borrowers" and together with the U.S.
Borrowers, the "Borrowers"), and BBH, (iii) that certain Guarantee, dated as of
September 13, 1999 (the "BBH Guarantee"), made by the U.S. Borrowers in favor of
BBH, pursuant to which the U.S. Borrowers guaranteed the obligations of the
French Borrowers under the French Credit Agreement, (iv) that certain Security
Agreement, dated as of September 13, 1999 (the "Security Agreement"), by and
among the U.S. Borrowers and BBH and (iv) that certain letter agreement
regarding the post-closing delivery of certain documentation and the
satisfaction of certain conditions, dated September 13, 1999 (the "Letter
Agreement").  The U.S. Credit Agreement, the French Credit Agreement, the BBH
Guarantee, the Security Agreement and the Letter Agreement are referred to
collectively herein as the "BBH Loan Documents."

     Reference is further made to (i) that certain Subordinated Note and Common
Stock Purchase Agreement, dated as of July 8, 1998 (the "Whitney Purchase
Agreement"), by and among WSDF, NMT and, for certain purposes, JHW, as amended
by that certain Amendment No. 1 dated April 14, 1999 ("Amendment No. 1") and as
further amended by that certain Amendment No. 2 dated September 13, 1999
("Amendment No. 2") (the Whitney Purchase Agreement as so amended,  the "Amended
Whitney Purchase Agreement"); (ii) that certain Subordinated Promissory Note,
dated as of July 8, 1998, payable to WSDF in the original principal amount of
$6,000,000 (the "Whitney Note") and (iii) that certain Guarantee and Collateral
Agreement, dated as of July 8, 1998 (the "Whitney Guarantee"), by the U.S.
Borrowers in favor of JHW, as Agent, as amended by Amendment No. 2 (as so
amended, the "Amended Whitney Guarantee").  The Amended Whitney Purchase
Agreement, the Whitney Note and the Amended Whitney Guarantee are referred to
collectively herein as the "Whitney Loan Documents."

     WHEREAS, NMT has informed BBH and Whitney that: (i) NMT and NMT
NeuroSciences (US), Inc. ("NMT US") intend to enter into a certain asset
purchase agreement (the "ISC Agreement") with Integra Selector Corporation
("ISC") pursuant to which, inter alia, NMT US shall sell to ISC the Assets (as
defined in the ISC Agreement), which transaction is intended to convey the
assets used in or related to the Ruggles(R) business of importing, developing,
manufacturing, customizing, marketing, selling and distributing surgical
instruments and (ii) NMT, NMT US, NMT Neurosciences Holdings (UK) Limited ("NMT
Holdings UK"), NMT Neurosciences (UK) Limited ("NMT UK"), Spembly

<PAGE>

Medical Limited ("SML"), Spembly Cryosurgery Limited ("SCL") and Swedemed AB
("SAB", and collectively with NMT UK, SML and SCL, the "Acquired Companies")
intend to enter into a purchase agreement (the "INH Agreement") with Integra
Neurosciences Holdings (UK) Limited ("Integra UK") and ISC pursuant to which,
inter alia, (a) NMT Holdings UK shall sell to Integra UK all of the capital
shares of NMT UK that are owned by NMT Holdings UK and (b) NMT US shall sell to
ISC the US-Based Assets (as defined in the INH Agreement), which US-Based Assets
include, in summary, those assets owned by NMT US or otherwise located in the
United States that are used or related to the products manufactured, assembled,
repaired, developed, created, invented or researched by or on behalf of the
Acquired Companies (which include, without limitation, the Selector Ultrasonic
Aspirator, cryosurgical and TNS product lines, products in the research and
development stage and other products identified in the Schedule of Products in
the INH Agreement). Each of BBH and Whitney acknowledges receipt of a copy of
the ISC Agreement and the INH Agreement. The transactions contemplated by the
ISC Agreement and the INH Agreement are referred to collectively herein as the
"Sale Transactions."

     WHEREAS, NMT intends to use a portion of the expected approximately
$12,000,000 of gross proceeds from the Sale Transactions to repay a portion of
its obligations under the BBH Loan Documents and the Whitney Loan Documents;

     WHEREAS, NMT has requested that BBH and Whitney consent to the Sale
Transactions and, in connection therewith, that (i) BBH and Whitney waive
compliance with certain financial and other covenants set forth in the BBH Loan
Documents and the Whitney Loan Documents respectively and (ii) BBH release its
security interest in the Assets and the US-Based Assets; and

     WHEREAS, BBH and Whitney have agreed to consent to the Sale Transactions
and waive compliance with certain covenants under the respective BBH  Documents
and Whitney Loan Documents and BBH has agreed to release its security interest
in the Assets and the US-Based Assets, all in accordance with the terms and
conditions set forth herein.

     NOW, THEREFORE, in consideration of the foregoing and the promises and
agreements set forth herein, the parties agree as follows:

     1.   BBH waives compliance by the U.S. Borrowers with the financial
covenants set forth in Section 6.09 of the U.S. Credit Agreement, which
covenants are incorporated by reference into the BBH Guarantee in Section 10(a)
thereof, for the fourth quarter of 1999, but only to the extent of the
deviations from the relevant financial covenants delivered in writing to BBH in
connection herewith. Whitney waives compliance by the U.S. Borrowers with the
financial covenants set forth in Section 9.8 of the Amended Whitney Purchase
Agreement for the fourth quarter of 1999.

     2.   BBH consents to the entering into agreements for and the consummation
of the Sale Transactions and, in connection therewith, waives any default under
the BBH Loan Documents that might otherwise be caused by or result from such
Sale Transactions, including but not limited to any default due to non-
compliance with Sections 5.03, 5.05 and 6.03 of the U.S. Credit Agreement (as

                                       2
<PAGE>

incorporated by reference into the BBH Guarantee).  Whitney consents to the
entering into agreements for and the consummation of the Sale Transactions and,
in connection therewith, waives any default under the Whitney Loan Documents
that might otherwise be caused by or result from such Sale Transactions,
including but not limited to any default due to non-compliance with Sections
9.1, 9.6, 9.7 or 9.10 of the Amended Whitney Purchase Agreement or Section 5.9
of the Amended Whitney Guarantee.

     3.   The consummation of the Sale Transactions shall not constitute a
"change of control" for purposes of Section 3(b) of the Whitney Note or
otherwise trigger mandatory prepayment of the Whitney Note.

     4.   BBH shall be paid such amount from the proceeds of the Sale
Transactions as is necessary to pay in full all monetary obligations of the
Borrowers under the French Credit Agreement and to reduce the outstanding
principal balance under the U.S. Credit Agreement as of the date of the Closing
(as defined in paragraph 5 below) to $2,000,000.  The parties agree that, upon
such reduction of the principal amount outstanding under the U.S. Credit
Agreement to $2,000,000 and such payment in full of all monetary obligations
under the French Credit Agreement, the amount of the Commitment (as defined in
the U.S. Credit Agreement) and the maximum aggregate principal amount of
permitted Senior Indebtedness (as defined in the Amended Whitney Purchase
Agreement) each shall be reduced to $2,000,000.  Without affecting the
effectiveness of the terms of the preceding sentence, the Borrowers agree that
they shall execute as soon as practicable after such payments have been made,
but in no event more than 10 business days after the date such payments have
been made: (i) an amendment to the U.S. Credit Agreement memorializing such
reduction of the Commitment to $2,000,000, in a form reasonably satisfactory to
BBH and (ii) an amendment to the Amended Whitney Purchase Agreement
memorializing such reduction of the permitted Senior Indebtedness to $2,000,000,
in a form reasonably satisfactory to Whitney.  In connection with the execution
of this agreement, BBH also shall receive a fee of $50,000 in cash payable on
the date hereof plus a warrant to purchase 20,000 shares of the common stock of
NMT exercisable at the listed price of NMT common stock as of the close of
business on the date hereof (the "Warrant").  The Warrant shall be delivered as
soon as practicable, but in no event more than 10 business days after the date
hereof, in a form reasonably satisfactory to BBH.  WSDF shall be paid up to a
total of $1,000,000 (but in no event less than $500,000) from the proceeds of
the Sale Transactions payable as follows: (i) a minimum of $500,000 shall be
paid by the close of business on the first business day after the Closing and
(ii) up to an additional $500,000 shall be paid within 10 business days after
the Closing, which amount shall be determined by NMT's management in good faith
based on the cash flow and budgeting needs of NMT and its subsidiaries.  BBH
consents to such payment of up to $1,000,000 to WSDF and, in connection
therewith, waives compliance with the subordination provisions and other payment
restrictions contained in the BBH Loan Documents and the Whitney Note solely to
the extent necessary to allow such payment to WSDF.  Additionally, BBH and
Whitney shall be paid their reasonable attorneys' fees in connection with this
transaction (the amount of such fees to be provided to NMT prior to the Closing)
by the close of business on the first business day after the Closing.

                                       3

<PAGE>

     5.   BBH agrees to release its security interest in the Assets and the US-
Based Assets in connection with the closing of the Sale Transactions (the
"Closing").  Such release shall be effective and self-executing simultaneously
with the Closing (such release shall be deemed to be effective immediately prior
to the conveyance of the Assets and the US-Based Assets, it being intended that
such assets shall be sold free and clear of any security interest or lien of
BBH).  BBH agrees to execute, at NMT's expense, any UCC-3 termination statements
and any other documentation reasonably requested by NMT to effectuate or
evidence such security interest terminations.  BBH acknowledges that it holds no
security interest in the capital stock of any of the Acquired Companies or in
any of the assets of any of the Acquired Companies.

     6.   BBH waives the defaults that would otherwise be caused by or result
from, or have been caused by or have resulted from, the failure of the Borrowers
heretofore to deliver the following item required by the Letter Agreement:  the
pledge of the stock of Image Technology Corp. (together with related stock
powers executed in blank); provided that the Borrowers shall deliver the
remaining documentation and satisfy the remaining conditions set forth in the
Letter Agreement on or before May 31, 2000.  The Borrowers acknowledge and agree
that if all of the documentation required to be delivered under the Letter
Agreement and all of the conditions required to be satisfied as set forth
therein are not so delivered and satisfied on or before May 31, 2000, it shall
constitute an immediate Event of Default under the U.S. Credit Agreement and the
French Credit Agreement.

     7.   The waivers by BBH and Whitney are limited to those described herein,
and nothing contained herein or in any other communication between any Borrower
and BBH or Whitney shall constitute a consent to any other deviation from the
terms of any of the BBH Loan Documents or Whitney Loan Documents.  Except as
expressly set forth herein, nothing contained in this agreement shall be deemed
to modify or amend any of the BBH Loan Documents or Whitney Loan Documents, each
of which remains in full force and effect, or constitute a course of dealing
among the Borrowers and BBH or Whitney.

     8.   The making of this agreement shall not be construed as: (i) creating
in favor of BBH a right to require its consent or approval to any future
modification, amendment or waiver of or under the Whitney Loan Documents or (ii)
creating in favor of Whitney a right to require its consent or approval to any
future modification, amendment or waiver of or under the BBH Loan Documents.

     9.   The payment and other obligations of the Borrowers hereunder that are
to be paid or performed after the date hereof shall not affect the validity or
effect of the waivers and consents given by BBH and Whitney herein in connection
with the Sale Transactions, it being intended that the buyers under the Sale
Transactions may rely on the finality of such waivers and consents.  The
foregoing sentence shall not affect or be deemed to affect the obligations of
the Borrowers to BBH and Whitney hereunder and any rights that BBH and Whitney
may have under the BBH Loan Documents and the Whitney Loan Documents
respectively.  This agreement shall be effective only upon the execution hereof
by BBH, Whitney and the Borrowers.

                                       4
<PAGE>

     WHEREFORE, the parties have executed this agreement as a document under
seal as of the date first written above.

BROWN BROTHERS HARRIMAN & CO.

By: /s/ Louise A. Coughlan
   ------------------------
Name:    Louise A. Coughlan
 Title:  Senior Vice President

WHITNEY SUBORDINATED DEBT FUND, L.P.

By: /s/ Daniel J. O'Brien
   ----------------------
 Name:  Daniel J. O'Brien
 Title: General Partner

J.H. WHITNEY & CO.

By: /s/ Daniel J. O'Brien
   ----------------------
 Name:  Daniel J. O'Brien
 Title: General Partner

NMT MEDICAL, INC.

By: /s/ Thomas M. Tully
   --------------------
 Name:  Thomas M. Tully
 Title: President

NMT HEART, INC.

By: /s/ Thomas M. Tully
   --------------------
Name:  Thomas M. Tully
Title: President

                                       5
<PAGE>

NMT INVESTMENTS CORP.

By: /s/ Thomas M. Tully
   --------------------
Name:  Thomas M. Tully
Title: President

NMT NEUROSCIENCES
(INTERNATIONAL), INC.

By: /s/ Thomas M. Tully
   --------------------
Name:  Thomas M. Tully
Title: President

NMT NEUROSCIENCES (US), INC.

By: /s/ Thomas M. Tully
   --------------------
Name:  Thomas M. Tully
Title: President

NMT NEUROSCIENCES (IP), INC.

By: /s/ Thomas M. Tully
   --------------------
Name:  Thomas M. Tully
Title: President

NMT NEUROSCIENCES
INNOVASIVE SYSTEMS, INC.

By: /s/ Thomas M. Tully
   --------------------
Name:  Thomas M. Tully
Title: President

                                       6
<PAGE>

NMT NEUROSCIENCES IMPLANTS
(FRANCE) SA

By: /s/ David A. Chazanovitz
   -------------------------
Name:  David A. Chazanovitz
Title: Director

NMT NEUROSCIENCES INSTRUMENTS
(FRANCE) SARL

By: /s/ David A. Chazanovitz
   -------------------------
Name:  David A. Chazanovitz
Title: Co-Manager

                                       7

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