FIRST AMENDMENT TO
             AMENDED AND RESTATED PREFERRED SHARES RIGHTS AGREEMENT

         This Amendment to Amended and Restated Preferred Shares Rights
Agreement (this "Amendment") is made as of August 30, 1999 by and between
CardioThoracic Systems, Inc., a Delaware corporation (the "Company"), and
Norwest Bank Minnesota, N.A., a national banking association (the "Rights
Agent").

         Pursuant to Section 27 of the Amended and Restated Preferred Shares
Rights Agreement (the "Agreement"), dated as of August 30, 1999, by and between
the Company and the Rights Agent, this Amendment is being executed by the
Company and the Rights Agent for the purpose of amending the Agreement as set
forth below:

         The Agreement is hereby amended as follows:

         1.       Section 1(a) shall be amended by inserting the following at
                  the end of Section 1(a):

                  "Notwithstanding the foregoing or any provision to the
                  contrary in this Agreement, none of Guidant Corporation
                  ("Guidant"), its subsidiaries, Affiliates or Associates or
                  permitted assignees or transferees under that certain Support
                  Agreement dated August 30, 1999, between Guidant and certain
                  stockholders of the Company (the "Support Agreement") is an
                  Acquiring Person pursuant to this Agreement by virtue of the
                  execution of the Agreement and Plan of Merger dated August 30,
                  1999 among Guidant, Clydesdale Acquisition Corp. and the
                  Company (the "Merger Agreement"), the Stock Option Agreement
                  dated August 30, 1999 among Guidant and the Company (the
                  "Option Agreement") and/or the Support Agreement or the
                  consummation of the Merger (as defined in the Merger
                  Agreement) or the other transactions contemplated by the
                  Option Agreement and/or the Support Agreement."

         2.       Section 1(l) shall be amended by inserting the following at
                  the end of Section 1(l):

                  "Notwithstanding the foregoing or any provision to the
                  contrary in this Agreement, a Distribution Date shall not
                  occur by reason of the execution of the Merger Agreement, the
                  Option Agreement and/or the Support Agreement, the
                  consummation of the Merger, or the consummation of the other
                  transactions contemplated by the Option Agreement and/or the
                  Support Agreement."

         3.       Section 1(hh) shall be amended by inserting the following at
                  the end of Section 1(hh):

                  "Notwithstanding the foregoing or any provision to the
                  contrary in this Agreement, a Shares Acquisition Date shall
                  not occur by reason of the execution of the Merger Agreement,
                  the Option Agreement and/or the Support Agreement, the
                  consummation


                                      -1-




                  of the Merger, or the consummation of the other
                  transactions contemplated by the Option Agreement and/or the
                  Support Agreement."

         4.       Section 1(oo) shall be amended by inserting the following at
                  the end of Section 1(oo):

                  "Notwithstanding the foregoing or any provision to the
                  contrary in this Agreement, a Triggering Event shall not occur
                  by reason of the execution of the Merger Agreement, the Option
                  Agreement and/or the Support Agreement, the consummation of
                  the Merger, or the consummation of the other transactions
                  contemplated by the Option Agreement and/or the Support
                  Agreement."

         5.       Section 1(r) shall be amended and restated in its entirety to
                  read as follows:

                  "(r) 'FINAL EXPIRATION DATE' shall mean the earlier of (i)
                  immediately prior to the Effective Time (as defined in the
                  Merger Agreement) of the Merger or (ii) January 28, 2007."

         6.       A new Section 35 shall be added to the Agreement to read as
                  follows:

                           "This Agreement shall be inapplicable to the Merger."

         7.       (a)      This Amendment may not be further amended without
                           the prior consent of Guidant in its sole discretion.

                  (b)      This Amendment shall be deemed to be entered into
                           under the laws of the State of Delaware and for all
                           purposes shall be governed by and construed in
                           accordance with the laws of such State applicable to
                           contracts to be made and performed entirely within
                           such State.

                  (c)      This Amendment may be executed in any number of
                           counterparts and each of such counterparts shall for
                           all purposes be deemed to be an original, and all
                           such counterparts shall together constitute but one
                           and the same instrument.

         8.       As amended hereby, the Agreement shall remain in full force
                  and effect.


                                      -2-





        IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed as of the day and year first above written.

CARDIOTHORACIC SYSTEMS, INC.                NORWEST BANK MINNESOTA, N.A.

By: /s/ RICHARD M. FERRARI                  By: /s/ JOHN BAKER
    ----------------------                      -------------------------

Name: Richard M. Ferrari                    Name: John Baker
     ---------------------                       ------------------------

Title:  President and CEO                   Title: Officer
      --------------------                        -----------------------


                                      -3-