Exhibit 10.20

FIRST AMENDMENT TO

EMPLOYMENT AGREEMENT

This First Amendment (the “Amendment”) to the Employment Agreement (the
“Agreement”) dated January 17, 2005, by and between CryoCor, Inc., a Delaware
corporation (the “Company”), and Edward F. Brennan (the “Executive”), is entered
into effective as of August 31, 2007 (the “Effective Date”).

RECITALS

WHEREAS, the Company and the Executive desire to amend the Agreement to extend
the severance period following a termination of the Executive’s employment
without Cause.

AGREEMENT

NOW THEREFORE, in consideration of the benefits and mutual promises hereinafter
set forth, the parties hereto agree as follows:

 

1. Capitalized terms used but not otherwise defined in this Amendment shall have
the meanings given such terms in the Agreement.

 

2. A new Section 3.3.5 is hereby inserted as follows:

(a) “3.3.5 280G. Anything in this Agreement to the contrary notwithstanding, if
any payment or benefit the Executive would receive under this Agreement, taken
together with any other agreement or benefit plan of the Company (including
stock options) (“Payment”) would (i) constitute a “parachute payment” within the
meaning of Section 280G of the Internal Revenue Code of 1986, as amended (the
“Code”), and (ii) but for this sentence, be subject to the excise tax imposed by
Section 4999 of the Code (the “Excise Tax”), then such Payment shall be equal to
the Reduced Amount. The “Reduced Amount” shall be either (x) the largest portion
of the Payment that would result in no portion of the Payment being subject to
the Excise Tax or (y) the largest portion, up to and including the total, of the
Payment, whichever amount, after taking into account all applicable federal,
state and local employment taxes, income taxes, and the Excise Tax (all computed
at the highest applicable marginal rate), results in the Executive’s receipt, on
an after-tax basis, of the greater amount of the Payment notwithstanding that
all or some portion of the Payment may be subject to the Excise Tax. If a
reduction in payments or benefits constituting “parachute payments” is necessary
so that the Payment equals the Reduced Amount, the reduction shall occur in the
order the Executive elects in writing, provided, however, that such election
shall be subject to Company approval if made on or after the date on which the
event that triggers the Payment occurs.

The accounting firm engaged by the Company for general audit purposes as of the
day prior to the effective date of the Change in Control shall perform the

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foregoing calculations. If the accounting firm so engaged by the Company is
serving as accountant or auditor for the individual, entity or group effecting
the Change in Control, the Company shall appoint a nationally recognized
accounting firm to make the determinations required hereunder. The Company shall
bear all expenses with respect to the determinations by such accounting firm
required to be made hereunder.

The accounting firm engaged to make the determinations hereunder shall provide
its calculations, together with detailed supporting documentation, to the
Executive and the Company within fifteen (15) calendar days after the date on
which the Executive’s right to a Payment is triggered (if requested at that time
by the Executive or the Company) or such other time as requested by the
Executive or the Company. If the accounting firm determines that no Excise Tax
is payable with respect to a Payment, either before or after the application of
the Reduced Amount, it shall furnish the Executive and the Company with an
opinion reasonably acceptable to the Executive that no Excise Tax will be
imposed with respect to such Payment. Any good faith determinations of the
accounting firm made hereunder shall be final, binding and conclusive upon the
Executive and the Company.”

 

3. Section 4.4.2 of the Agreement is hereby amended and restated in its entirety
as follows:

“4.4.2 Without Cause. If the Company terminates the Executive’s employment
without Cause, the Company shall pay the Executive’s base salary and accrued and
unused vacation earned through the date of termination, at the rate in effect at
the time of termination subject to standard deductions and withholdings. In
addition, upon the Executive’s execution of a Release (as defined in
Section 4.4.3 below), the Executive shall receive i) the equivalent of fifteen
(15) months of the Executive’s then current Base Salary less standard deductions
and withholdings, paid on the Company’s regular payroll dates and in accordance
with its regular payroll practices; ii) provided the Executive timely elects
COBRA health insurance continuation coverage, reimbursement of COBRA premiums
for a period of fifteen (15) months following termination; and iii) accelerated
vesting of the Options specified in Section 3.3 of this Agreement such that the
Options shall be deemed vested as to a number of shares equal to that which
would have been vested had the Executive remained in the continuous service of
the Company in accordance with the Plan for a period of fifteen (15) months
following the termination of his employment.”

 

4. A new Section 4.4.3 is hereby inserted as follows:

“4.4.3 Release. Notwithstanding the provisions of Sections 3.3.4 and 4.4.2, the
Executive’s entitlement to any and all compensation and benefits under
Sections 3.3.4 and 4.4.2 is expressly conditioned on the Executive’s execution
and delivery to the Company (and the expiration of any revocation period) of an
effective waiver and release of claims (a form of which is attached hereto as
Exhibit A) (a “Release”) within the time period set forth therein (but in no
event

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later than forty-five (45) days after the date of termination), which shall be
material to the Company’s obligation to provide any such compensation and
benefits.”

 

5. A new Section 4.6 is hereby inserted as follows:

“4.6 Application of Code Section 409A. Compensation and benefits payable under
the Agreement, to the extent of payments made from the date of the Executive’s
termination through March 15th of the calendar year following such termination,
are intended to constitute separate payments for purposes of
Section 1.409A-2(b)(2) of the Treasury Regulations and thus payable pursuant to
the “short-term deferral” rule set forth in Section 1.409A-1(b)(4) of the
Treasury Regulations; to the extent such payments are made following said
March 15th, they are intended to constitute separate payments for purposes of
Section 1.409A-2(b)(2) of the Treasury Regulations made upon an involuntary
termination from service and payable pursuant to Section 1.409A-1(b)(9)(iii) of
the Treasury Regulations, to the maximum extent permitted by said provision,
with any excess amount being regarded as subject to the distribution
requirements of Section 409A(a)(2)(A) of the Code, including, without
limitation, the requirement of Section 409A(a)(2)(B)(i) of the Code that payment
to the Executive be delayed until 6 months after separation from service if the
Executive is a “specified employee” within the meaning of the aforesaid section
of the Code at the time of such separation from service.”

 

6. Except as specifically amended by this Amendment, the terms and conditions of
the Agreement shall remain in full force and effect.

 

7. This Amendment is made in California. This Amendment shall be construed and
interpreted in accordance with the internal laws of the State of California.

 

8. This Amendment may be executed in two or more counterparts, each of which
shall be deemed an original, but all of which together shall constitute one and
the same instrument.

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IN WITNESS WHEREOF, the parties have executed this Amendment as of the Effective
Date.

 

CRYOCOR, INC. By:   /s/ Gregory J. Tibbitts

 

Name:   Gregory J. Tibbitts

 

Title:   Chief Financial Officer and VP, Finance

 

/s/ Edward F. Brennan Edward F. Brennan, Ph.D.