Document:

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                                                                   EXHIBIT 10.73

                   [FORM OF IMAGING CENTER SECURITY AGREEMENT]

                               SECURITY AGREEMENT
                                  [CENTER NAME]

      This Security Agreement ("Security Agreement") is made as of the ____ day
of November, 2001 by and between [P.C. NAME] ("PC") and [RAYTEL ENTITY NAME]
("Manager"; and, together with PC, "Pledgors"), in favor of HEALTHCARE BUSINESS
CREDIT CORPORATION, a Delaware corporation with an address at 700 East Gate
Drive, Suite 100, Mount Laurel, New Jersey 08054 ("Secured Party").

                                   BACKGROUND

      A. Manager is operator of a diagnostic imaging center located at [LOCATION
ADDRESS] (the "Imaging Center").

      B. PC is a medical practice.

      C. PC and Manager are parties to a certain [TITLE OF AGREEMENT BETWEEN
P.C. AND MANAGER] dated [DATE OF AGREEMENT BETWEEN P.C. AND MANAGER] (as
amended, renewed or replaced from time to time, "Agreement"), a true and correct
copy of which is attached hereto as Exhibit "A," providing for the operation of
the Imaging Center.

      D. Pursuant to the terms of a Loan and Security Agreement dated as of the
date hereof (as may be amended, restated, supplemented or modified from time to
time, the "Loan Agreement"), Secured Party has extended to Manager, Raytel
Medical Corporation ("RMC") and certain of their affiliates (Manager, RMC and
such affiliates are hereinafter referred to as "Borrowers") a credit facility in
the original maximum principal amount of $15,000,000.00 (the "Loan").

      E. [INSERT APPLICABLE RELATIONSHIP, E.G., MANAGER IS A SUBSIDIARY OF RMC
AND IT] is contemplated that a portion of the proceeds of the Loan will be
indirectly available to finance the operations of the Imaging Center. Each
Pledgor acknowledges that it will be materially benefited as a result thereof.

      F. Secured Party desires to obtain, and each of the Pledgors desires to
grant to Secured Party, a first priority security interest in the Collateral (as
defined below) to secure all of the Obligations (as defined below) of the
Borrowers to Secured Party.

NOW, THEREFORE, with the foregoing Background incorporated by reference and made
part hereof, Pledgors and Secured Party, intending to be legally bound hereby,
promise and agree as follows:

      1. Each of the Pledgors hereby grants to Secured Party a continuing lien
on and security interest in the following property of such Pledgor and in the
following property which may be jointly owned by Pledgors, whether now or
hereafter owned and wherever located (collectively, the "Collateral"):

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            (i) all accounts (including without limitation, the Accounts)
whether now existing or hereafter arising or acquired, (ii) all contract rights,
instruments, chattel paper, documents, general intangibles, rights, remedies,
guarantees and collateral evidencing, securing or otherwise relating to such
accounts, including without limitation, all rights of enforcement and
collection, (iii) all lockboxes, all collection accounts and other accounts into
which any of the proceeds and/or payments on the accounts are deposited, all
funds received thereby or deposited therein, and any checks or instruments from
time to time representing or evidencing the same, (iv) all books and records of
Pledgors evidencing or relating to such accounts, (v) all information and data
compiled or derived by Pledgors with respect of such accounts (other than any
such information and data subject to legal restrictions of patient
confidentiality) and (vi) all collections, receipts and other proceeds (cash and
noncash) derived from any of the foregoing.

      For purposes hereof "Account" means (a) the third party reimbursable
portion of accounts receivable owing to the Pledgors arising out of the delivery
by the Pledgors of medical, surgical, diagnostic or other professional or
medical or dental services, including all rights to reimbursement under any
agreements with a third party obligor, (b) all other healthcare insurance
receivables and accounts as defined in the Uniform Commercial Code as in effect
in the State of New Jersey (the "UCC"), (c) all rights, remedies, guarantees,
and security interests in respect of the foregoing, all rights of enforcement
and collection, all books and records evidencing or related to the foregoing,
and all rights under this Security Agreement in respect of the foregoing, (d)
all information and data compiled or derived by the Pledgors in respect of such
accounts receivable (other than any such information and data subject to legal
restrictions of patient confidentiality), and (e) all proceeds of any of the
foregoing.

      2. The security interest hereby granted by Pledgors secures (collectively,
the "Obligations") all now existing or hereafter arising debts, obligations,
covenants, and duties of payment or performance of every kind, matured or
unmatured, direct or contingent, owing, arising, due or payable to Secured Party
by or from any Borrower arising out of the Loan Agreement or any other document
executed and delivered in connection therewith (collectively, such documents and
the Loan Agreement are referred to herein as the "Loan Documents").

      3. The Pledgors hereby agree that if the location of the Collateral
changes from the location identified in Background paragraph A hereof, the
Pledgors will immediately notify the Secured Party in writing of the additions
or changes to the locations of the Collateral.

      4. Each of the Pledgors covenants that it shall do, obtain, make, execute
and deliver all such additional and further acts, things, deeds, assurances and
instruments as Secured Party may require to vest in and assure to Secured Party
its rights hereunder and in or to the Collateral, and the proceeds thereof.

      5. Each Pledgor represents, warrants and covenants that it has not granted
or suffered or will grant or suffer the imposition of a lien or security
interest upon the Collateral, other than the lien granted herein in favor of
Secured Party, and that it has not and will not use any portion thereof in any
manner inconsistent with this Security Agreement.

      6. At the request of the Secured Party, the Pledgors will join with the
Secured Party in executing one or more financing, continuation or amendment
statements pursuant to the UCC

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in form satisfactory to the Secured Party. A carbon, photographic or other copy
of this Security Agreement or of a UCC-1 financing statement may be filed as and
in lieu or a UCC-1 financing statement.

      7. The happening of any of the following events or conditions shall
constitute an "Event of Default" hereunder:

            (a) Dissolution, termination of existence, insolvency, business
suspension or failure, appointment of a receiver of any part of the property of
a Pledgor, assignment for the benefit of creditors by a Pledgor, or the
commencement of any proceedings under any federal bankruptcy or state insolvency
laws (now or hereafter enacted for the relief of Pledgors) by or against a
Pledgor, or

            (b) The failure of either Pledgor to comply with the terms of this
Agreement; or

            (c) The occurrence of an Event of Default under the Loan Agreement.

      Upon the occurrence and during the continuance of an Event of Default, the
Secured Party may declare all Obligations secured hereby immediately due and
payable and shall have, in addition to any remedies provided herein, in any
other Loan Document or by any applicable law, all the remedies of a secured
party under the UCC, as permitted therein, and the Secured Party may (i) dispose
of the Collateral on the Pledgors' premises, (ii) require the Pledgors to
assemble the Collateral and make it available to the Secured Party at a place
reasonably designated by the Secured Party and/or (iii) subject to applicable
laws and regulations governing payment of Medicare/Medicaid receivables, take
possession of the Collateral and notify all account debtors of Secured Party's
security interest in the Collateral and require payment under the Collateral to
be made directly to Secured Party and exercise all rights of a secured party
with respect to the Collateral and collect, sue for and receive payment on all
accounts, and settle, compromise and adjust the same on any term as may be
satisfactory to Secured Party, in its respective sole and absolute discretion
and such party may do all of the foregoing with or without judicial process
(including, without limitation, notifying the United States Postal Authorities
to redirect mail addressed to Pledgors to an address designated by Secured
Party). Unless the Collateral is of a type customarily sold on a recognized
market, the Secured Party will give the Pledgors reasonable notice of the time
and place of any public sale thereof or of the time after which any private sale
or any other intended disposition thereof is to be made. The requirements of
reasonable notice shall be met if such notice is mailed, postage prepaid, to the
business address of the Pledgors shown in this Security Agreement at least
fifteen (15) days before the time of the intended sale or disposition. Expenses
of retaking, holding, preparing for sale, selling or the like shall include the
Secured Party's reasonable attorneys' fees and legal expenses, incurred or
expended by the Secured Party to enforce any payment due it under this Security
Agreement either as against the Pledgors or in the prosecution or defense of any
action, or concerning any matter growing out of or connection with the subject
matter of this Security Agreement and the Collateral pledged hereunder.

      8. The Secured Party shall not be deemed to have waived any of the Secured
Party's rights hereunder or under any other agreement, instrument or paper
signed by the Pledgors unless

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such waiver is in writing and signed by the Secured Party. No delay or omission
on the part of the Secured Party in exercising any right shall operate as a
waiver of such right or any other right. A waiver on any one occasion shall not
be construed as a bar to or waiver of any right or remedy on any other occasion.

      9. Each of the Pledgors does hereby make, constitute and appoint any
officer or agent of the Secured Party as such Pledgor's true and lawful
attorney-in-fact, with power to sign and file on such Pledgor's behalf any and
all UCC financing statements, and, after an Event of Default, to endorse the
name of such Pledgor or any of such Pledgor's officers or agents upon any notes,
checks, drafts, money orders, or other instruments of payment or Collateral that
may come into the possession of the Secured Party in full or part payment of any
amounts owing to the Secured Party; granting to such Pledgor's said attorney
full power to do any and all things necessary to be done in and about the
premises as fully and effectually as such Pledgor might or could do, including
the right to compromise, settle and release all claims and disputes with respect
to the Collateral, and such Pledgor hereby ratifies all that said attorney shall
lawfully do or cause to be done by virtue hereof. This power of attorney shall
be irrevocable for the life of this Security Agreement and all transactions
hereunder.

      10. All provisions herein shall inure to, and become binding upon, the
successors, representatives, receivers, trustees and assigns of the parties;
provided, however, that neither Pledgor will delegate its duty of performance
hereunder without the Secured Party's prior written consent. The term "Security
Agreement", as used in this instrument, shall mean and include this Security
Agreement, all amendments and supplements to any of the foregoing, and all
assignments, instruments and documents submitted to the Secured Party in
connection with any transaction between the Pledgors and the Secured Party. Each
of the Pledgors hereby waives notice of default, and presentment, demand,
protest, and notice of dishonor as to any instrument. Each of the Pledgors
hereby releases Secured Party from all claims for loss or damage caused by any
act or omission on the part of Secured Party, its officers, agents, and
employees, except for willful misconduct.

      11. This Security Agreement and all acts, transactions, agreements,
certificates, assignments and transfers thereunder, and all rights of the
parties hereto, shall be governed as to their validity, enforcement,
construction and effect, and in all other respects, by New Jersey law. The
provisions hereof are severable, and the invalidity or unenforceability of any
provision shall not affect or impair the remaining provisions which shall
continue in full force and effect. No modification hereof shall be binding or
enforceable unless in writing and signed on behalf of the party against whom
enforcement is sought.

      12. Each of the Pledgors irrevocably consents to the exclusive
jurisdiction of any state or Federal court located in the State of New Jersey in
any and all actions and proceedings whether arising hereunder or under any other
agreement or undertaking and irrevocably agrees to service of process by
certified mail, return receipt requested to the address of Pledgors set forth
herein. PLEDGORS AND SECURED PARTY AS AN INDEPENDENT COVENANT IRREVOCABLY WAIVE
JURY TRIAL AND THE RIGHT THERETO IN ANY AND ALL DISPUTES BETWEEN PLEDGORS AND
SECURED PARTY WHETHER HEREUNDER OR UNDER ANY OTHER AGREEMENTS, NOTES, PAPERS,
INSTRUMENTS OR DOCUMENTS, WHETHER SIMILAR OR DISSIMILAR.

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      13. This Security Agreement may be executed in one or more counterparts
which, when taken together, will constitute one and the same document.

      IN WITNESS WHEREOF, the parties hereto, intending to be legally bound
hereby, have set their hands and seals on the day and year first above written.

                                         PLEDGORS:

[P.C. NAME] P.C.                         [RAYTEL ENTITY NAME]

By:                                      By:
    -------------------------------          -----------------------------------
    Name:                                    Name:
    Title:                                   Title:

                                         SECURED PARTY:

                                         HEALTHCARE BUSINESS CREDIT
                                         CORPORATION

                                         By:
                                             -----------------------------------
                                             Name:
                                             Title:

                                       5<PAGE>
                                                                   Exhibit 10.74

                       KEY MANAGEMENT RETENTION AGREEMENT

        THIS KEY MANAGEMENT RETENTION AGREEMENT (the "Agreement"), dated as of
December 5, 2001 (the "Effective Date"), is made and entered into by and between
RAYTEL MEDICAL CORPORATION, a Delaware corporation (the "Company"), and JOHN F.
LAWLER, JR. (the "Executive").

                                    RECITALS:

        A. The Executive is currently employed, as an at-will employee, as the
Company's Vice President and Chief Financial Officer;

        B. The Company is considering various potential strategic transactions
that could result in a Change of Control (as hereinafter defined); and

        C. The parties desire to provide an incentive for the continued
employment of the Executive in order to facilitate a potential Change of
Control.

        NOW, THEREFORE, the parties agree as follows:

        1. Definitions. For purposes of this Agreement, the following terms
shall be defined as follows:

               1.1 "Cause" shall exist in the event of the Executive's (i)
willful and repeated neglect of his duties as an employee of the Company (other
than as a result of a physical disability not related to substance abuse), (ii)
conviction of a crime involving moral turpitude, (iii) commission of any act of
fraud or dishonesty against the Company, or (iv) breach of the Executive's
obligations under any employment agreement or Proprietary Information and
Inventions Agreement between the Executive and the Company which, if curable, is
not cured within ten (10) days following notice of such breach by the Company.

               1.2 A "Change of Control" of the Company shall occur upon: (i) a
merger, consolidation or other reorganization involving the Company, or a tender
offer, exchange offer or other transaction or series of transactions involving
the acquisition of securities of the Company where, in any such case, the
holders of voting securities of the Company immediately prior to such
transaction or series of transactions own less than 50% of the voting securities
of the surviving or successor entity, or its parent, immediately following such
transaction or series of transactions; (ii) the sale of all or substantially all
of the Company's assets; or (iii) the sale of all or substantially all of the
capital stock or assets of any subsidiary or subsidiaries of the Company which
accounted for 40% or more of the Company's consolidated revenues for the
preceding fiscal year.

               1.3 "Good Reason" shall exist in the event that, other than under
circumstances involving Cause or the Executive's total disability (as defined
pursuant to the Company's long-term disability insurance plan covering the
Executive if any such plan is then in effect, or otherwise as determined by the
Company's Board of Directors), the Company, without the Executive's prior
written consent; (i) materially alters or reduces the Executive's duties,
responsibilities and status with the Company from those which exist as of the
Effective Date of

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this Agreement; (ii) reduces the level of compensation or benefits that the
Executive is earning as an employee of the Company; (iii) requires the Employee,
as a condition to his continued employment, to be based more than 100 miles from
the location where he is based as of the Effective Date; or (iv) requires the
Employee, as a condition to his continued employment, to perform illegal or
fraudulent acts or omissions.

               1.4 A "Qualifying Employment Agreement" shall mean a written
agreement for the continued employment by the Executive in a position with
duties and responsibilities substantially comparable to his current position,
with compensation and other benefits substantially comparable, in the aggregate,
to his current compensation and benefits, and providing for a term of at least
one year and severance benefits equal to at least one-half of his annual base
salary in the event of his involuntary termination other than for Cause or his
voluntary termination for Good Reason.

        2. Retention and Severance Arrangement.

               2.1 Retention Bonus. In the event the Company effects a Change of
Control during the term of this Agreement, the Executive shall be entitled to
receive a cash bonus (the "Retention Bonus") in an amount equal to one-half of
his then-effective annual base salary, payable in a single lump sum promptly
upon the fulfillment of the conditions set forth in Section 2.2.

               2.2 Conditions to Receipt of Retention Bonus.

                      (a) In order for the Executive to be eligible to receive
the Retention Bonus, the following conditions must be met:

                             (i) The Executive must be continuously employed by
the Company on a full-time basis between the Effective Date of this Agreement
and the effective date of the Change of Control; and

                             (ii) Either of the following conditions must occur:
(A) the Executive remains continuously employed by the Company, Raytel Cardiac
Services, Inc., the acquiring entity or another subsidiary or affiliate of the
acquiring entity during the six-month period following the effectiveness of the
Change of Control (provided, however, that no Retention Bonus shall be payable
if, during such six-month period, the Executive and one or more of such entities
enter into a Qualifying Employment Agreement); or (B) prior to the end of such
six-month period, the Executive's employment by one of such entities is
terminated involuntarily by such entity other than for Cause or voluntarily by
the Executive with Good Reason.

               2.3 Reduction. The Retention Bonus payable to the Executive shall
be reduced by an amount equal to any severance payments paid to the Executive
under the terms of any Company policy regarding severance benefits or any
employment agreement between the Executive and the Company, not including the
value associated with any acceleration of vesting of options or stock as a
result of a Change of Control.

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               2.4 Acceleration of Option Vesting. The option agreements between
the Company and the Executive shall be amended to provide that the vesting
provisions of all outstanding options to purchase the Company's Common Stock
held by the Executive shall be accelerated so that such options will vest and
become exercisable, in full, upon the Change of Control, to the extent any such
option agreements do not currently provide for such acceleration of vesting.

               2.5 Annual Bonus. The Retention Bonus is not intended to replace
or reduce any bonus to which the Executive may be entitled under the Company's
existing annual incentive bonus program, which shall continue to be administered
in accordance with the Company's existing policies.

               2.6 Not an Employment Agreement. The Executive is currently
employed as an "at will" employee. This Key Management Retention Agreement is
not an employment agreement, and nothing contained herein shall limit the rights
of the Company or the Employee to terminate the Employee's employment at any
time for any reason.

               2.7 Term. The term of this Agreement shall be twelve (12)
calendar months from the Effective Date of this Agreement.

        3. General

               3.1 Successors and Assigns. The provisions of this Agreement
shall inure to the benefit of and be binding upon the Company, the Executive and
each and all of their respective heirs, legal representatives, successors and
assigns. The duties, responsibilities and obligations of the Executive under
this Agreement shall be personal and not assignable or delegable by the
Executive in any manner whatsoever to any person, corporation, partnerships,
firm, company, joint venture or other entity. The Executive may not assign,
transfer, convey, mortgage, pledge or in any other manner encumber the
compensation or other benefits to be received by him or any rights which he may
have pursuant to the terms and provisions of this Agreement. The Company
covenants and agrees to require that any successor to the Company through a
Change of Control shall agree to honor the obligations of the Company under this
Agreement.

               3.2 Waiver. No waiver of any breach of any warranty,
representation, agreement, promise, covenant, paragraph, term or provision of
this Agreement shall be deemed to be a waiver of any preceding or succeeding
breach of the same or any other warranty, representation, agreement, promise,
covenant, paragraph, term or provision of this Agreement. No extension of the
time for the performance of any obligation or other act required or permitted by
this Agreement shall be deemed to be an extension of the time of the performance
of any other obligation or any other act required or permitted by this
Agreement.

               3.3 Entire Agreement. This Agreement, and the other agreements
referred to herein, including the Company's benefit plans, are the sole,
complete and entire contract, agreement and understanding between the Company
and the Executive concerning the subject matter hereof. Except as otherwise
provided herein, this Agreement supersedes any and all prior

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contracts, agreements, plans, agreements in principle, correspondence, letters
of intent, understandings, and negotiations, whether oral or written, concerning
the subject matter hereof.

               3.4 Amendments. No amendment, modification, waiver, or consent
relating to this Agreement will be effective unless and until it is embodied in
a written document signed by the Company and by the Executive.

               3.5 Counterparts. The Agreement may be executed by the Company
and by the Executive in counterparts, each of which shall be deemed an original
and which together shall constitute one instrument.

               3.6 Headings. The headings contained in this Agreement are for
reference purposes only and shall not in any manner whatsoever affect the
construction or interpretation of this Agreement or be deemed a part of this
Agreement for any purpose whatsoever.

               3.7 Severability. To the extent that any section, term,
provision, sentence, phrase, clause or word of this Agreement shall be found to
be illegal or unenforceable for any reason, such section, term, provision,
sentence, phrase, clause or word shall be modified or deleted in such a manner
as to make this Agreement, as so modified, legal and enforceable under
applicable laws. The remainder of this Agreement shall continue in full force
and effect.

               3.8 Applicable Law. This Agreement and each and every provision
of this Agreement shall be interpreted solely pursuant to the internal laws of
the State of California without regard to any conflicts of law principles
thereof.

               3.9 Construction. The language of this Agreement shall for all
purposes be construed as a whole, according to its fair meaning, not strictly
for or against the Executive or the Company, without regard to the identity or
status of any person or persons who drafted all or any portion of this
Agreement.

               3.10 Notices. Any notices to be given pursuant to this Agreement
by either party to the other party may be effected by personal delivery or by
registered or certified mail, postage prepaid with return receipt requested.
Mailed notices shall be addressed to the parties at the addresses stated below,
but each party may change its or his address by written notice to the other in
accordance with this Section 3.10. Notices delivered personally shall be deemed
received on the date of delivery. Notices delivered by mail shall be deemed
received on the third business day after the mailing thereof.

        Mailed notices to the Executive shall be addressed as follows:

               John F. Lawler, Jr.
               27 Silver Lane
               Enfield, Connecticut 06082

        Mailed notices to the Company shall be addressed as follows:

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               Raytel Medical Corporation
               2755 Campus Drive, Suite 200
               San Mateo, California 94403-2515
               Attention:  Chief Executive Officer

               3.11 Arbitration. Any and all controversies, disputes and/or
claims in any manner arising out of or relating to this Agreement shall be
settled solely be arbitration in accordance with the Commercial Arbitration
Rules of the American Arbitration Association. Such arbitration proceeding shall
take place in the state and county of the Company's office where the Executive
is based. Judgment on any decision rendered by the arbitrator may be entered in
any court having jurisdiction thereof. Each party shall bear its own attorney's
fees and expenses and other costs in any arbitration proceeding. All
administrative fees and the fee of the arbitrator shall be borne by the parties
equally. The arbitration provisions set forth in this Section 3.11 are intended
by the Executive and by the Company to be absolutely exclusive for all purposes
whatsoever, and applicable to each and every controversy, dispute or claim in
any manner arising out of or relating to this Agreement, the meaning,
application or interpretation of this Agreement, any breach or claimed breach
thereof or any voluntary or involuntary termination of this Agreement with or
without cause, including, without limitation, any such controversy, dispute or
claim which, if pursued through any state or federal court or administrative
agency, would arise at law, in equity or pursuant to statutory, regulatory or
common law rules, regardless of whether such dispute, controversy or claim would
arise in or from contract, tort or any other legal or equitable theory or basis.

        IN WITNESS WHEREOF, the Company and the Executive have executed this
Agreement as of the date first set forth above.

RAYTEL MEDICAL CORPORATION

By:_____________________________________      __________________________________
   Richard F. Bader                           John F. Lawler, Jr.
   Chairman and Chief Executive Officer

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