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                                                                   EXHIBIT 10.13


                                   AMENDMENT NO. 8
                               TO EMPLOYMENT AGREEMENT



    THIS AMENDMENT NO. 8 TO EMPLOYMENT AGREEMENT (the "Amendment") is made and
entered into at Santa Barbara, California, on the date hereinafter set forth by
and between DAVID E. MAI (hereinafter referred to as the "Employee") and PDT
CARDIOVASCULAR, INC., a Delaware Corporation (hereinafter referred to as the
"Employer").

WHEREAS:

    A.   The Employer and the Employee are parties to an Employment Agreement
effective as of  FEBRUARY 1, 1991, and Amendments No. 1 through 7 thereto (the
"Employment Agreement").

    B.   The parties hereto wish to amend the Employment Agreement in certain
respects.

    NOW, THEREFORE,  in consideration of the premises, promises and
representations hereinafter contained, it is agreed as follows:

    1.   Section 1.1 of the Employment Agreement is hereby amended to read as
follows:

         "1.1      POSITION AND DUTIES

                   The Corporation does hereby employ the Employee and the
Employee hereby accepts such employment as PRESIDENT OF PDT CARDIOVASCULAR,
INC., EFFECTIVE AS OF SEPTEMBER 1, 1992 AND PRESIDENT OF PDT, INC. EFFECTIVE AS
OF MAY 17, 1996, upon the terms and provisions set forth in this Agreement.  The
Employee shall perform all the duties assigned to him by the Corporation, shall
observe and comply with the Corporation's rules and regulations regarding the
performance of his duties, and shall carry out and perform all orders,
directions, and policies stated to him by the Corporation periodically, either
orally or in writing.  The Employee shall carry out the duties assigned to him
in a trustworthy, businesslike, and loyal manner.  The Employee agrees that this
Agreement may be terminated as provided in Paragraph 7 hereof."

    2.   Effective as of MAY 17, 1996, the Employee Compensation stated in
Exhibit A to the Agreement shall be One Hundred and Sixty Two Thousand Dollars
($162,000) per annum.

    3.   In all other respects, the Employment Agreement is hereby ratified,
confirmed and approved in its entirety.

    4.   The Effective Date of this Amendment is MAY 17, 1996.


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                                         AMENDMENT NO. 8 TO EMPLOYMENT AGREEMENT
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    IN WITNESS WHEREOF, the parties hereto have executed this Amendment
effective on the date written above.

                                       THE CORPORATION:
                                       PDT, INC.
                                       a Delaware Corporation

                                       By: /s/ Gary S. Kledzik
                                          -----------------------------------
                                               Gary S. Kledzik, Ph.D.
                                               C.E.O. and Chairman

                                       EMPLOYEE:

                                       /s/  David E. Mai
                                          -----------------------------------
                                            David E. Mai


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