Form 4
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

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1. Name and Address of Reporting Person*
Chase, Howard E		 2. Issuer Name and Ticker or Trading Symbol
Thoratec Corporation   (THOR)

6. Relationship of Reporting Person(s) to Issuer

(Check all applicable)      

_X_ Director                            ___ 10% Owner
___ Officer (give title below)   ___ Other (specify below)
(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

04/28/2003
(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
Common Stock 04/28/2003   S   2152 D $13.5000   D  
Common Stock 04/28/2003   S   1500 D $13.4700   D  
Common Stock 04/28/2003   S   1500 D $13.4900 0 D  
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).
 
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 (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 V (A) (D) Date
Exercisable		 Expiration
Date		 Title Amount
or
Number
of Shares
                               
Explanation of Responses:
** 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 		04/28/2003 
Date
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