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CAMBRIDGE
 HEART

                                                                   Exhibit 10.33

                                      November 18, 1999

Eric Dufford
VP Sales and Marketing
Cambridge Heart, Inc.
One Oak Park Drive
Bedford, MA 01730


Re:   Severance Agreement

Dear Eric:

      Cambridge Heart, Inc. (the "Company"), recognizes that, as is the case
with many publicly-held corporations, the possibility of a change in control of
the Company exists and that such possibility, and the uncertainty and questions
it may raise among key personnel, may result in the departure or distraction of
key personnel to the detriment of the Company and its stockholders. The Board of
Directors has determined that while there are no current plans for the Company
to engage in a change of control transaction, appropriate steps be taken to
reinforce and encourage the continued employment and dedication of the Company's
key personnel without distraction from the possibility of a change of control
and related events and circumstances.

      Accordingly, the Company agrees as follows:

     1.   In the event that the Company terminates your employment without
Cause, then the following shall apply:

          .  You will continue to be paid your salary for six (6) months after
             termination at the rate in effect on the termination date.

          .  You will continue for six (6) months to be enrolled in the health
             insurance program you were enrolled in as of the termination date.

          .  The vesting of all stock options you hold as of the termination
             date will be accelerated as follows: the number of shares under all
             such options that would have become vested (i,e., exercisable)
             during the twelve (12) month period following the termination date
             shall become exercisable; you must exercise all options (including
             the accelerated portion) within the time periods set forth in your
             option agreement(s) and the applicable option plan.
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  2.  In the event that a Change in Control occurs, the following shall apply:

      .  The vesting of all stock options you hold as of the Change in Control
         Date will be accelerated as follows: fifty percent (50%) of the number
         of shares under all such options that were not vested (i.e.,
         exercisable) as of the Change in Control Date shall become exercisable
         as of the Change in Control Date; you must exercise all options
         (including the accelerated portion) within the time periods set forth
         in your options agreement(s) and the applicable option plan.

  3.  In the event that a Change in Control occurs and, within twelve (12)
      months after the Change in Control Date, your employment (either with the
      Company or the successor/acquiror) is terminated without Cause or you
      terminate your employment for Good Reason, then the following shall
      apply:

      .  You will continue to be paid your salary for twelve (12) months after
         termination at the rate in effect on the termination date.

      .  You will continue for twelve (12) months to be enrolled in the health
         insurance program you were enrolled in as of the termination date.

      .  The vesting of all stock options you hold as of the Change in Control
         Date will be accelerated as follows: one hundred percent (100%) of the
         number of shares under all such options that were not vested (i.e.,
         exercisable) as of the termination date shall become exercisable as of
         the termination date; you must exercise all options (including the
         accelerated portion) within the time periods set forth in your options
         agreement(s) and the applicable option plan.

  All capitalized terms used in this letter agreement have the meanings set
forth in Exhibit A
         ---------

  This agreement supercedes all other agreements concerning severance.


                                      Sincerely yours,

                                      CAMBRIDGE HEART, INC.

                                      By:/s/ Jeffrey Arnold
                                         ------------------------
                                      Title: President
                                             --------------------

AGREED:
/s/ Eric Dufford
-------------------------
Employee

CAMBRIDGE HEART, INC. * 1 Oak PARK DRIVE * BEDFORD, MA 01730 * PHONE 781-271-
1200 * FAX 781-275-8431

                            www.cambridgeheart.com
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                                   EXHIBIT A
                                   ---------

      1. "Change in Control" means an event or occurrence set forth in any one
          ----------------
or more of subsections (a) through (c) below (including an event or occurrence
that constitutes a Change in Control under one of such subsections but is
specifically exempted from another such subsection):

         (a)   the acquisition by an individual, entity or group (within the
meaning of Section 13(d)(3) or 14(d)(2) of the Securities Exchange Act of 1934,
as amended (the "Exchange Act")) (a "Person") of beneficial ownership of any
capital stock of the Company if, after such acquisition, such Person
beneficially owns (within the meaning of Rule 13d-3 promulgated under the
Exchange Act) 50% or more of either (i) the then-outstanding shares of common
stock of the Company (the "Outstanding Company Common Stock") or (ii) the
combined voting power of the then-outstanding securities of the Company entitled
to vote generally in the election of directors (the "Outstanding Company Voting
Securities"); provided, however, that for purposes of this subsection (a), the
following acquisitions shall not constitute a Change in Control; (i) any
acquisition directly from the Company, (ii) any acquisition by the Company or
(iii) any acquisition by any employee benefit plan (or related trust) sponsored
or maintained by the Company or any corporation controlled by the Company; or

        (b)    such times as the Continuing Directors (as defined below) do not
constitute a majority of the Board (or, if applicable, the Board of Directors of
a successor corporation to the Company), where the term "Continuing Directors"
means at any date a member of the Board (i) who was a member of the Board on the
date of the execution of this Agreement or (ii) who was nominated or elected
subsequent to such date by at least a majority of the directors who were
Continuing Directors at the time of such nomination or election or whose
election to the Board was recommended or endorsed by at least a majority of the
directors who were Continuing Directors at the time of such nomination or
election; or

        (c)   the consummation of a merger, consolidation, reorganization,
recapitalization or statutory share exchange involving the Company or a sale or
other disposition of all or substantially all of the assets of the Company (a
"Business Combination"), unless, immediately following such Business
Combination, all or substantially all individuals and entities who were the
beneficial owners of the Outstanding Company Common Stock and Outstanding
Company Voting Securities immediately prior to such Business Combination
beneficially own, directly or indirectly, more than 50% of the then-outstanding
shares of common stock and the combined voting power of the then-outstanding
securities entitled to vote generally in the election of directors,
respectively, of the resulting or acquiring corporation in such Business
Combination in substantially the same proportions as their ownership,
immediately prior to such Business Combination, of the Outstanding Company
Common Stock and Outstanding Company Voting Securities, respectively.

      2. "Change in Control Date" means the first date on which a Change in
          ----------------------
Control occurs.

                                       2
CAMBRIDGE HEART, INC. * 1 OAK PARK DRIVE * BEDFORD MA 01730 * PHONE 781-271-1200
                              * FAX: 781-275-8431
                            www.cambridgeheart.com
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      3. "Cause" means
          -----

          (a) the Employee's willful and continued failure to substantially
perform [his/her] reasonable assigned duties (other than any such failure from
incapacity due to physical or mental illness or any failure after the Employee
gives notice of termination for Good Reason), which failure is not cured within
30 days after a written demand for substantial performance is received by the
Employee from the Board of Directors of the Company which specifically
identifies the manner in which the Board of Directors believes the Employee has
not substantially performed the Employee's duties; or

         (b)  the Employee's wilful engagement in illegal conduct or gross
misconduct which is materially and demonstrably injurious to the Company.

          For purposes of this Section 3, no act or failure to act by the
Employee shall be considered "willful" unless it is done, or omitted to be done,
in bad faith and without reasonable belief that the Employee's action or
omission was in the best interest of the Company.


      4. "Good Reason" means the occurrence, without the Employee's written
          -----------
consent, of any of the events or circumstances set forth in clauses (a) through
(d) below. Notwithstanding the occurrence of any such event or circumstance,
such occurrence shall not be deemed to constitute Good Reason if, prior to the
notice of termination given by the Employee in respect thereof, such event or
circumstance has been fully corrected and the Employee has been reasonably
compensated for any losses or damages resulting therefrom (provided that such
right of correction by the Company shall only apply to the first notice of
termination for Good Reason given by the Employee).

         (a) the assignment to the Employee of duties inconsistent in any
material respect with Employee's position (including status, offices, titles,
location and reporting requirements), authority or responsibilities in effect
immediately prior to the earliest to occur of (i) the Change in Control Date,
(ii) the date of the execution by the Company of the initial written agreement
or instrument providing for the Change in Control or (iii) the date of the
adoption by the Board of Directors of a resolution providing for the Change in
Control (with the earliest to occur of such dates referred to herein as the
"Measurement Date"), or any other action or omission by the Company which
results in a diminution in such position, authority or responsibilities;

        (b)  a reduction in the Employee's annual base salary as in effect on
the Measurement Date or as the same was or may  be increased from time to time;

        (c)  the failure by the Company to (i) continue in effect any material
compensation or benefit plan or program (including without limitation any life
insurance, medical, health and accident or disability plan and any vacation
program or policy) (a "Benefit Plan") in which the Employee participates or
which is applicable to the Employee immediately prior to the Measurement Date,
unless an equitable arrangement (embodied in an ongoing substitute or
alternative plan) has been made with respect to such plan or program, (ii)
continue the Employee's participation therein (or in such substitute or
alternative plan) on a basis not materially less favorable, both in terms of the
amount of benefits provided and the level of the Employee's participation
relative to other participants, than the basis existing immediately prior to the
Measurement Date or (iii) award cash bonuses to the Employee in amounts and in a
manner substantially consistent with past practice in light of the Company's
financial performance.

                                       3





        Cambridge Heart, Inc. * 1 Oak Park Drive * Bedford, MA 01730 *
                    Phone: 781-271-1200 * FAX: 781-275-8431

                            www.cambridgeheart.com
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    (D)  any failure of the Company to pay or provide to the Employee any
portion of the Employee's compensation or benefits due under any Benefit Plan
within seven days of the date such compensation or benefits are due, or any
material breach by the Company of any employment agreement with the Employee.


                                       4

CAMBRIDGE HEART, INC.* 1 OAK PARK DRIVE * BEDFORD, MA 01730 * PHONE 781-271-1200
                              * FAX 781-275-8431

                        www.cambridgeheart.com