SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                   -----------

                                  SCHEDULE 13D
                                 (Rule 13d-101)

             INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
             TO RULE 13d-l(a) AND AMENDMENTS THERETO FILED PURSUANT
                                TO RULE 13d-2(a)

                                (Amendment No. 3)

                              Thoratec Corporation
                              ---------------------
                                (Name of Issuer)

                      Common Stock, no par value per share
                      ------------------------------------
                         (Title of Class of Securities)

                                   885175 30 7
                          ---------------------------
                                 (CUSIP Number)

                             Seth H. Hoogasian, Esq.
                                 General Counsel
                                 (781) 622-1000
                           Thermo Electron Corporation
                                 81 Wyman Street
                        Waltham, Massachusetts 02454-9046
                          ---------------------------

                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                February 15, 2002
                          ---------------------------
             (Date of Event Which Requires Filing of This Statement)

     If the filing  person has  previously  filed a statement on Schedule 13G to
report the  acquisition  that is the subject of this Schedule 13D, and is filing
this  schedule  because  of Rule  13d-1(e),  13d-1(f)  or  13d-1(g),  check  the
following box [ ].

     Note.  Schedules  filed in paper format shall include a signed original and
five copies of the schedule, including all exhibits. See Rule 13d-7(b) for other
parties to whom copies are to be sent. (Continued on following pages)






-------------------------                      ---------------------------------

 CUSIP NO. 885175 30 7                 13D                   Page 2 of 6 Pages
-------------------------                      ---------------------------------


-------- -----------------------------------------------------------------------

1.       NAMES OF REPORTING PERSONS
         I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)

         Thermo Electron Corporation
         04-2209186
-------- -----------------------------------------------------------------------

2.       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*              (a) [ ]
                                                                        (b) [ ]
-------- -----------------------------------------------------------------------

3.       SEC USE ONLY

-------- -----------------------------------------------------------------------

4.       SOURCE OF FUNDS*

         SC
-------- -----------------------------------------------------------------------

5.       CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
         TO ITEM 2(d) or 2(e)                  ?

-------- -----------------------------------------------------------------------

6.       CITIZENSHIP OR PLACE OF ORGANIZATION
         State of Delaware
---------------------------- -------- ------------------------------------------

     NUMBER OF SHARES        7.       SOLE VOTING POWER
BENEFICIALLY OWNED BY EACH                   4,953,765
   REPORTING PERSON WITH
                             -------- ------------------------------------------

                             8.       SHARED VOTING POWER
                                             2,731,779
                             -------- ------------------------------------------

                             9.       SOLE DISPOSITIVE POWER
                                             7,685,544
                             -------- ------------------------------------------

                             10.      SHARED DISPOSITIVE POWER
                                             -0-
---------------------------- -------- ------------------------------------------

11.        AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
           7,685,544

---------- ---------------------------------------------------------------------

12.        CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
           SHARES*                                                           [ ]
---------- ---------------------------------------------------------------------

13.        PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
           13.4%

---------- ---------------------------------------------------------------------

14.        TYPE OF REPORTING PERSON*

           CO
---------- ---------------------------------------------------------------------
                                         *SEE INSTRUCTIONS BEFORE FILLING OUT!





     Thermo  Electron  Corporation,  a  Delaware  corporation  ("the  "Reporting
Person"),  hereby  amends its  statement  on Schedule 13D relating to the common
stock,  no par value per share (the  "Common  Stock"),  of Thoratec  Corporation
(formerly known as Thoratec Laboratories Corporation),  a California corporation
(the "Company").

     ITEM 2. Identity and Background.

     Item 2 is hereby amended and restated as follows:

     This  Amendment  is being filed by the  Reporting  Person  pursuant to Rule
13d-2 to reflect the change of information  previously  reported under Item 5 of
its Schedule 13D, as amended.

     The  principal  business  address  and  principal  office  address  of  the
Reporting Person is 81 Wyman Street, Waltham, Massachusetts 02454-9046.

       The Reporting Person is a leading provider of analytical and monitoring
instruments used in a broad range of applications, from life sciences research
to telecommunications to food, drug, and beverage production.

       Appendix A attached to hereto sets forth with respect to each executive
officer and director of the reporting Person the following information:

          (a)  name;
          (b)  business address;
          (c)  present   principal   occupation  or  employment  and  the  name,
               principal  business  and  address  of any  corporation  or  other
               organization  in which  such  employment  is  conducted;  and
          (d)  citizenship.

To the knowledge of the Reporting  Person,  there is no person who may be deemed
to be a controlling person of the Reporting Person.

     During the last five  years,  neither  the  Reporting  Person  nor,  to the
knowledge of the  Reporting  Person,  any  executive  officer or director of the
Reporting Person has been convicted in a criminal proceeding  (excluding traffic
violations or similar misdemeanors).

     During the last five  years,  neither  the  Reporting  Person  nor,  to the
knowledge of the  Reporting  Person,  any  executive  officer of director of the
Reporting  Person  has  been a party  to a civil  proceeding  of a  judicial  or
administrative  body of  competent  jurisdiction  which  resulted in a judgment,
decree  or final  order  enjoining  future  violations  of,  or  prohibiting  or
mandating activities subject to, Federal or State securities laws or finding any
violation with respect to such laws.

     ITEM 5. Interest in Securities of the Issuer.

       Item 5 is hereby amended and restated in its entirety as follows:

     (a) As of the date of this Amendment,  the Reporting  Person owns 7,685,544
shares of Common Stock which represents 13.4% of the outstanding Common Stock of
the Company,  based upon the total Common Stock  outstanding  as reported on the

                                 (Page 3 of 6)



Company's  Annual  Report on Form 10-K for the year ended  December 29, 2001. Of
the 7,685,544  shares of Common Stock currently  owned by the Reporting  Person,
24,047  shares of Common  Stock are  subject to options to acquire  such  shares
granted by the  Reporting  Person  pursuant to its director  and employee  stock
option plans. Information with respect to the beneficial ownership of the shares
of Common Stock of the other persons named in Item 2 is set forth in Appendix A.
Except  as set  forth in this  Item 5, to the best  knowledge  of the  Reporting
Person,  none of the parties  named in Item 2 owns any of the  Company's  Common
Stock.

     On February 15, 2002, the Reporting  Person completed the sale of 6,875,000
shares of Common Stock to Lehman Brothers,  Inc., as  representative  of several
underwriters, pursuant to an Underwriting Agreement dated February 12, 2002. The
Reporting Person received gross proceeds of $105,050,000 or $15.28 per share. In
connection with this  transaction,  the Company and the Reporting  Person agreed
that (i) the restrictions on resale contained in the Shareholder Agreement dated
as of October 3, 2000  between the Company and the  Reporting  Person  would not
apply to the sale of the shares of Common  Stock by the  Reporting  Person;  and
(ii) the  Registration  Rights Agreement dated as of October 3, 2000 between the
Company  and  the  Reporting  Person  be  amended  to  eliminate  the  Company's
obligation  to register  4,828,240  shares of Common Stock held by the Reporting
Person on or before February 14, 2002.

     In connection with the Company's redemption on March 11, 2002 of its 4 3/4%
Convertible  Subordinated  Debentures (the  "Debentures"),  the Company redeemed
$1,500,000  principal amount of Debentures held by the Reporting  Person.  These
Debentures were convertible into 39,869 shares of Common Stock.

     (b) With  respect  to  2,731,779  shares  of  Common  Stock of the  Company
beneficially  owned by the Reporting  Person,  the  Reporting  Person shares the
power to vote all of such shares with the  Company  pursuant to the  Shareholder
Agreement,  as  more  fully  described  in Item 4  above.  With  respect  to the
remainder of the shares of Common Stock of the Company beneficially owned by the
Reporting  Person,  the  Reporting  Person  has the sole  power to vote all such
shares.  Subject  to the  terms  of the  Shareholder  Agreement,  as more  fully
described in Item 4 above, the Reporting Person has the sole power to dispose of
the shares of Common Stock  beneficially owned by it. With respect to the shares
of Common Stock of the Company  beneficially owned by the other persons named in
Item 2,  except as set forth in  Appendix A, each such person has the sole power
to vote all of such shares and the sole power to dispose of all of such shares.

     Item 1 sets forth the Company's name and state of incorporation  along with
the address of its  principal  business  and  principal  office.  The  Company's
principal business is the research, development,  manufacturing and marketing of
medical devices for circulatory support and vascular graft applications.  To the
best knowledge of the Reporting Person,  during the last five years, the Company
(i) has  not  been  convicted  in any  criminal  proceeding  (excluding  traffic
violations  or  similar  misdemeanors)  and  (ii)  was  not a  party  to a civil
proceeding of a judicial or  administrative  body of competent  jurisdiction  as
result  of which it was or is  subject  to a  judgment,  decree  or final  order
enjoining future violations of, or prohibiting or mandating  activities  subject

                                 (Page 4 of 6)


to,  Federal or State  securities  laws or finding any violation with respect to
such laws.

     (c) Except as  described  below in this Item 5 and in Item 4, which item is
incorporated  herein by  reference,  neither  the  Reporting  Person nor, to the
knowledge of the Reporting  Person,  any person named in Appendix A beneficially
has effected any transactions in Common Stock during the past 60 days.

     (d) None.

     (e) Not applicable.


                                 (Page 5 of 6)



                                   SIGNATURES

     After  reasonable  inquiry and to the best of my  knowledge  and belief,  I
certify that the information  set forth in this statement is true,  complete and
correct.


                                        Dated:  April 1, 2002

                                        THERMO ELECTRON CORPORATION


                                        By:     /s/ Theo Melas-Kyriazi
                                        ----------------------------------------
                                        Name:   Theo Melas-Kyriazi
                                        Title:  Vice President and Chief
                                                Financial Officer





                                 (Page 6 of 6)





                                   APPENDIX A

Thermo Electron Corporation

     The  name,  present  principal  occupation  or  employment  and  beneficial
ownership of shares of common stock of Thoratec  Corporation  (the "Company") of
each  director and executive  officer of Thermo  Electron  Corporation  ("Thermo
Electron") is set forth below.  Unless otherwise noted, all such individuals are
citizens of the United States.  Unless  otherwise noted, the business address of
each  executive  officer  and  director of Thermo  Electron is 81 Wyman  Street,
Waltham, Massachusetts 02454-9046.

Directors


                                                                                                            

-------------------------------------- ---------------------------------------- ---------------------------------------------
                                                                                   Beneficial Ownership of Shares of the
                                                                                            Company Common Stock
--------------------------------------                                          ------------- ----------------- -------------
                                                                                                   Shares
                                                                                                 Underlying
                                                                                                  Options
                                                                                                Exercisable        Total
       Name/Present Principal                                                   Shares Held    Prior to April    Beneficial
      Occupation or Employment                    Business Address                Outright        1, 2002        Ownership
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Peter O. Crisp                                                                           0                 0             0
Vice Chairman of Rockefeller
Financial Services, Inc.
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Frank Jungers                           822 NW Murrray
Private consultant on business and      Suite 242                                       0               835           835
energy matters.                         Portland, Oregon 97229
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
John L. LaMattina                       Pfizer, Inc.
Executive Vice President of Pfizer      50 Pequot Avenue                                0                 0             0
Global Research and Development         New London, Connecticut 06230
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Jim P. Manzi
Chairman of Stonegate Capital.                                                          0                 0             0

-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Robert A. McCabe                        Pilot Capital Corporation                   9,393               835        10,228
Chairman of Pilot Capital               444 Madison Avenue
Corporation.                            Suite 2103
                                        New York, New York 10022
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Robert W. O'Leary                                                                       0                 0             0
Chairman and Chief Executive Officer
of The Sagamore Group.
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Hutham S. Olayan                        Olayan America Corporation
President and a director of Olayan      505 Park Avenue                                 0               835           835
America Corporation.                    Suite 1100
                                        New York, New York 10022
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Michael E. Porter                       Harvard Business School
Bishop William Lawrence                 Soldiers Field Road                             0                 0             0
University Professor at                 Boston, Massachusetts 02163
Harvard Business School.
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Elaine S. Ullian                        Boston Medical Center
President and Chief Executive           Talbot 1                                        0                 0             0
Officer of Boston Medical Center.       One Boston Medical Center Place
                                        Boston, Massachusetts 02118
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Richard F. Syron
Chief Executive Officer and Chairman                                                    0                 0             0
of the Board of Thermo Electron

-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Marijn E. Dekkers(1)                                                                     0                 0             0
President, Chief Operating Officer
and Director of Thermo Electron
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------

(1) Mr. Dekkers is a citizen of The Netherlands

                                  (Page I - 1)




Executive Officers Who are Not Directors

         No person is a controlling stockholder of Thermo Electron.

-------------------------------------- ---------------------------------------- ---------------------------------------------
                                                                                   Beneficial Ownership of Shares of the
                                                                                            Company Common Stock
--------------------------------------                                          ---------------------------------------------
                                                                                ------------- ----------------- -------------
       Name/Present Principal                     Business Address              Shares Held        Shares          Total
                                                                                                 Underlying
                                                                                                  Options
                                                                                                Exercisable
                                                                                               Prior to April    Beneficial
      Occupation or Employment                                                    Outright        1, 2002        Ownership
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Theo Melas-Kyriazi(2)                                                                2,960            16,700        19,660
Vice President and Chief Financial
Officer of Thermo Electron
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Guy Broadbent(3)                                                                         0                 0             0
Vice President of Thermo Electron,
President, Optical Technologies
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Barry S. Howe                                                                            0                 0             0
Vice President of Thermo Electron,
President, Measurement and Control
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Marc Casper                                                                              0                 0             0
Vice President of Thermo Electron,
President, Life Sciences
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Seth H. Hoogasian                                                                        0                 0             0
Vice President, General Counsel and
Secretary of Thermo Electron
-------------------------------------- ---------------------------------------- ------------- ----------------- -------------
Peter E. Hornstra                                                                        0                 0             0
Corporate Controller and Chief
Accounting Officer of Thermo Electron
------------------------------------------------------------------------------- ------------- ----------------- -------------
All directors and current executive officers as a group                             12,353            19,205        31,558
------------------------------------------------------------------------------- ------------- ----------------- -------------


(2) Mr. Melas-Kyriazi is a citizen of Greece.

(3) Mr. Broadbent is a citizen of the United Kingdom.

                                  (Page I -2)