SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

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


                                    FORM 8-K


                                 CURRENT REPORT

                       Pursuant to Section 13 or 15(d) of
                       the Securities Exchange Act of 1934



                                 Date of Report
                       (Date of earliest event reported):

                               September 29, 1998

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


                            THERMO CARDIOSYSTEMS INC.
             (Exact name of Registrant as specified in its charter)


Massachusetts                    1-10114                    04-3027040
(State or other               (Commission              (I.R.S. Employer
jurisdiction of               File Number)             Identification Number)
incorporation or
organization)


470 Wildwood Street
Woburn, Massachusetts                                            01888
Address of principal executive offices)                       (Zip Code)


                                 (781) 932-8668
                         (Registrant's telephone number
                              including area code)


<PAGE>


      This Form 8-K contains forward-looking statements that involve a number of
risks and  uncertainties.  Important  factors that could cause actual results to
differ  materially from those indicated by such  forward-looking  statements are
set forth under the heading "Forward-looking Statements" in Exhibit 13 to Thermo
Cardiosystems  Inc.'s  Annual  Report on Form 10-K for the year ended January 3,
1998. These include risks and uncertainties  relating to: regulatory  approvals,
reimbursement by insurers,  medical community  acceptance,  technological change
and competition,  intellectual  property  rights,  availability of materials and
components,   limited  experience  in  commercializing  LVAS  products,  product
liability,  international  operations and sales, and the potential impact of the
year 2000 on processing date-sensitive information.

Item 5.     Other Events

      On September 29, 1998, Thermo Cardiosystems Inc. ("Thermo  Cardiosystems")
issued a press release  announcing  that the U.S.  Food and Drug  Administration
("FDA")  has  approved  Thermo   Cardiosystems'   electric   HeartMate(R)   left
ventricular-assist  system  ("LVAS")  for  commercial  sale as a bridge to heart
transplant.  The electric HeartMate LVAS is an implantable  heart-assist  system
designed to allow heart-transplant candidates to return home while waiting for a
donor heart.

      In addition,  on September 29, 1998,  Baxter Healthcare  Corporation,  the
principal U.S. operating subsidiary of Baxter International Inc., announced that
it has  received  pre-market  approval  from  the FDA for  its  Novacor(R)  Left
Ventricular Assist System in the United States as a bridge to heart transplant.

Item 7.     Financial Statements, Pro Forma Financial Information and Exhibits

      (a)    Financial Statements of Business Acquired: not
            applicable.

      (b)   Pro Forma Financial Information: not applicable.

      (c)   Exhibits: not applicable.


<PAGE>


                                    SIGNATURE



      Pursuant to the  requirements of the Securities  Exchange Act of 1934, the
Registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned, thereunto duly authorized, on this 30th day of September, 1998.



                                          THERMO CARDIOSYSTEMS INC.


                                          By:/s/ Kenneth J. Apicerno
                                             Kenneth J. Apicerno
                                             Treasurer
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SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549

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

                                    FORM 8-K

                                 CURRENT REPORT

                       Pursuant to Section 13 or 15(d) of
                       the Securities Exchange Act of 1934

                                 Date of Report
                       (Date of earliest event reported):

                               September 29, 1998

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

                            THERMO CARDIOSYSTEMS INC.
             (Exact name of Registrant as specified in its charter)

Massachusetts                    1-10114                    04-3027040
(State or other               (Commission              (I.R.S. Employer
jurisdiction of               File Number)             Identification Number)
incorporation or
organization)

470 Wildwood Street
Woburn, Massachusetts                                            01888
Address of principal executive offices)                       (Zip Code)

                                 (781) 932-8668
                         (Registrant's telephone number
                              including area code)
This Form 8-K contains forward-looking statements that involve a number of
risks and  uncertainties.  Important  factors that could cause actual results to
differ  materially from those indicated by such  forward-looking  statements are
set forth under the heading "Forward-looking Statements" in Exhibit 13 to Thermo
Cardiosystems  Inc.'s  Annual  Report on Form 10-K for the year ended January 3,
1998. These include risks and uncertainties  relating to: regulatory  approvals,
reimbursement by insurers,  medical community  acceptance,  technological change
and competition,  intellectual  property  rights,  availability of materials and
components,   limited  experience  in  commercializing  LVAS  products,  product
liability,  international  operations and sales, and the potential impact of the
year 2000 on processing date-sensitive information.

Item 5.     Other Events

      On September 29, 1998, Thermo Cardiosystems Inc. ("Thermo  Cardiosystems")
issued a press release  announcing  that the U.S.  Food and Drug  Administration
("FDA")  has  approved  Thermo   Cardiosystems'   electric   HeartMate(R)   left
ventricular-assist  system  ("LVAS")  for  commercial  sale as a bridge to heart
transplant.  The electric HeartMate LVAS is an implantable  heart-assist  system
designed to allow heart-transplant candidates to return home while waiting for a
donor heart.

      In addition,  on September 29, 1998,  Baxter Healthcare  Corporation,  the
principal U.S. operating subsidiary of Baxter International Inc., announced that
it has  received  pre-market  approval  from  the FDA for  its  Novacor(R)  Left
Ventricular Assist System in the United States as a bridge to heart transplant.

Item 7.     Financial Statements, Pro Forma Financial Information and Exhibits

      (a)    Financial Statements of Business Acquired: not
            applicable.

      (b)   Pro Forma Financial Information: not applicable.

      (c)   Exhibits: not applicable.
SIGNATURE

      Pursuant to the  requirements of the Securities  Exchange Act of 1934, the
Registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned, thereunto duly authorized, on this 30th day of September, 1998.

                                          THERMO CARDIOSYSTEMS INC.

                                          By:/s/ Kenneth J. Apicerno
                                             Kenneth J. Apicerno
                                             Treasurer