Form 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL
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1. Name and Address of Reporting Person* Nelson, Jeffrey	2. Issuer Name and Ticker or Trading Symbol Thoratec Corporation (THOR)		6. Relationship of Reporting Person(s) to Issuer (Check all applicable) ___ Director ___ 10% Owner _X_ Officer (give title below) ___ Other (specify below) President, Cardiovascular Division
(Last) (First) (Middle) 6035 Stoneridge Drive	3. I.R.S. Identification Number of Reporting Person, if an entity (voluntary)	4. Statement for Month/Day/Year 02/25/2003
(Street) Pleasanton, CA 94588		5. If Amendment, Date of Original (Month/Day/Year)	7. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person
(City) (State) (Zip)	Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transactions (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. * If the form is filed by more than one reporting person, see Instructions 4(b)(v).
	Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.	(Over) SEC 1474 (9-02)

FORM 4 (continued)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1.
Title of Derivative Security
(Instr.3)

2.
Conversion or
Exercise
Price of
Derivative
Security

3.
Transaction
Date
(Month/
Day/Year)

3A.
Deemed Execution
Date, if any
(Month/
Day/Year)

4.
Transaction Code
(Instr. 8)

5.
Number of Derivative
Securities
Acquired (A) or Disposed of (D)
(Instr.3,4
and 5)

6.
Date Exercisable
and Expiration Date
(Month/Day/Year)

7.
Title and Amount of
Underlying Securities
(Instr. 3 and 4)

8.
Price of
Derivative
Security
(Instr. 5)

9.
Number of
Derivative
Securities
Beneficially
Owned Following Reported Transaction(s)
(Instr. 4)

10.
Ownership
Form of
Derivative
Security:
Direct (D) or Indirect (I)
(Instr. 4)

11.
Nature of
Indirect
Beneficial
Ownership
(Instr. 4)

Code

(A)

(D)

Date
Exercisable

Expiration
Date

Title

Amount
or
Number
of Shares

Incentive Stock Option (right to buy)

$8.78

02/25/2003

6,000

(1)

02/25/2013

Common Stock

6,000

Non-Qualified Stock Option (right to buy)

$8.78

02/25/2003

18,000

(1)

02/25/2013

Common Stock

18,000

Explanation of Responses:

(1) Shares vest 25% per year over 4 years commencing 1 year after the option grant date

**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).	/s/ M. Wayne Boylston **Signature of Reporting Person Attorney-In-Fact	02/25/2003 Date
Note:	File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

Potential persons who are to respond to the collection of information contained in this form are not
required to respond unless the form displays a currently valid OMB Number.

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NELSON JEFFREY 4