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                                                                   EXHIBIT 10.52



                        AMENDMENT TO EMPLOYMENT AGREEMENT


        This Amendment to Employment Agreement (the "Amendment") is made and
entered into as of March 17, 1997, by and between The Heart Institute of Port
St. Lucie, Inc. (hereinafter referred to as "Employer"), and DAVID E.
WERTHEIMER, M.D. (hereinafter referred to as the "Employee").

                                   WITNESSETH:

        WHEREAS, Employer and Employee have entered into an Employment Agreement
(the "Agreement") dated January 1, 1996; and

        WHEREAS, Employer and Employee desire to amend the Agreement by changing
the covenant not to compete to comply with revisions in the law of the State of
Florida pertaining to such covenants;

        NOW THEREFORE, in consideration of the mutual benefits accruing to the
parties, Employer and Employee agree that Article XII of the Agreement is hereby
amended to read in its entirety as set forth below:

               XII.     COVENANT NOT TO COMPETE

                        Employee expressly covenants with the Employer as
follows:

                        During the employment period, if the Employee shall, for
               any reason other than permanent retirement from the practice of
               medicine, permanently or temporarily leave the employ of the
               Employer, Employee hereby agrees, unconditionally, that he shall
               not in any manner whatsoever, directly or indirectly, as partner,
               employee, agent, principal, independent contractor, consultant,
               owner, or in any other capacity whatsoever establish, maintain,
               manage or occupy any office or premises for, and/or engage in the
               practice of the medical specialties of cardiology, internal
               medicine or any other type of medical specialty or medical
               practice engaged in by the Employer, for a period of not less
               than two (2) years the "Restricted Period") after termination of
               employment, within an area of a radius of fifty (50) miles from
               any office or offices of the Employer presently existing or
               existing at the time of the termination of Employee's employment
               (the "Restricted Area").

                      The Employer and the Employee agree that it is impossible
               to determine with any reasonable accuracy the amount of damages
               Employer would incur upon breach of this provision. Accordingly,
               in the event Employee breaches this provision, the Employee does
               hereby unconditionally covenant and agree with the Employer that
               the Employee shall pay, forthwith, the sum of Three Hundred
               Thousand Dollars ($300,000) as liquidated damages (the
               "Liquidated Damages") to the Employer upon written notice and
               demand, and in any event within three (3) days of the receipt of
               said notice by the Employee.





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                      In the event Employee refuses to pay said sum or
               unreasonably delays the payment of same, the Employer shall have
               the unqualified option to sue and recover from Employee the
               aforesaid sum together with its reasonable attorney's fees and/or
               obtain an injunction against the Employee to enforce the medical
               practice prohibitions of this covenant, together with Employer's
               reasonable attorney's fees. It is the express intent and purpose
               of this provision that the Employee shall in no way compete with
               the Employer in every particular as set forth herein.
               Notwithstanding the above, the Employer, in lieu of accepting he
               Liquidated Damages, shall have the right of injunctive relief.
               Such injunction may, in the discretion of the court, be granted
               without bond being required. If injunctive relief for any reason
               whatsoever is not available, then the Liquidated Damages, shall
               be paid as set forth above.

                      The Employee further acknowledges that the use of specific
               patient lists or direct solicitation of existing patients shall
               be presumed to be an irreparable injury to the Employer and may
               be specifically enjoined.

                      In the event Employer brings a legal action or other
               proceedings against Employee for enforcement of any provision of
               this Agreement, the calculation of the non-compete period shall
               not include the period of time commencing with the filing of
               legal action or other proceeding to enforce the provisions or
               provisions of this Agreement through the date of final judgment
               or final resolution, including all appeals, if any, of such legal
               action. The existence of any claim or cause of action by Employee
               against the Employer predicated on this Employment Agreement
               shall not constitute a defense to the enforcement by the Employer
               of this covenant not to compete.

                      Employee hereby acknowledges that this covenant not to
               compete is legally authorized under Section 542.335, Florida
               Statutes, a copy of which is attached to this Amendment and made
               a part hereof as Exhibit Number 1. The Employee hereby
               acknowledges that he has read Section 542.335, understands its
               meaning, and has had the legal significance of it explained to
               him by an independent attorney of Employee's choosing. Employee
               acknowledges that Employer has legitimate business interests to
               justify the restrictions placed on him under this Agreement,
               including without limitation:

               (a)   Employee possesses or will possess confidential business or
                     professional information pertaining to Employer and its
                     business, the use of which by Employee outside of his
                     employment relationship with Employer could cause
                     substantial harm to Employer and its business;

               (b)   Employer has or will have substantial relationships with
                     existing or prospective patients who utilize the services
                     of Employer and the physicians and staff employed by
                     Employer, which relationships could be 





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                     substantially disrupted if Employee were to compete with
                     Employer in the Restricted Area during the Restricted
                     Period; and

               (c)   Employer has created patient goodwill in connection with
                     the conduct of its professional practice under its trade
                     name within the Restricted Area, which goodwill could be
                     substantially diluted if Employee were to compete with
                     Employer in the Restricted Area during the Restricted
                     Period.

                      Employee further acknowledges that the restrictions on his
               activity as contained in this Agreement are legitimate and
               reasonable, as to distance and monetary amount, are required for
               the Employer's reasonable protection, and are a material
               inducement to the Employer to enter into this Employment
               Contract. Notwithstanding anything contained herein to the
               contrary, the provisions contained in this Section XII shall
               survive the expiration and term of this Agreement.

                      Employee further acknowledges that if enjoined from
               practicing medicine during a reasonably limited time or within a
               reasonably limited area, such restriction will not in any way
               jeopardize the health and welfare of the Employee's patients
               because the patients will be able to continue to receive proper
               medical care and treatment from the Employer after the Employee
               leaves, or from other physicians in the area practicing the same
               type of medical specialty.

                      Employee agrees that Employer may assign this Agreement to
               an entity that acquires or succeeds to the interests of Employer,
               and in such event, the Employer's assignee or successor is
               expressly authorized to enforce the provisions of this Section
               XII.

        IN WITNESS WHEREOF, the parties have executed this Amendment on the day
and year first above written.
                                    EMPLOYER:
                                    THE HEART INSTITUTE OF PORT ST.  LUCIE, INC.

                                    By:  /s/  David E. Wertheimer
                                        ----------------------------------------

                                    EMPLOYEE:

                                            /s/  David E. Wertheimer
                                    --------------------------------------------
                                                 DAVID E. WERTHEIMER, M.D.





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