<PAGE>
 
                                                                   EXHIBIT 10.21


                              SECURITY AGREEMENT

     THIS SECURITY AGREEMENT (the "Agreement") is made and entered into as of
the 28th day of October, 1996 by and between Cardiac Control Systems, Inc., a
Delaware Corporation ("Debtor" or "Company") and Bart C. Gutekunst, an
individual ("Secured Party").

     WHEREAS, Debtor is obligated to pay Secured Party the sum of One Hundred
Eight Thousand Two Hundred Forty-Six Dollars and 64/100 ($108,246.64) (the
"Obligation") pursuant to a secured promissory note dated of even date herewith
(the "Note"), which Obligation represents $100,000.00 advanced to the Debtor by
Secured Party and $8,246.64 in expenses incurred by Secured Party in connection
with making such advance, which expenses shall be itemized in a writing and
delivered to the Company.

     NOW THEREFORE, in consideration of the mutual promises made herein between
the parties hereto, and other valuable consideration, the receipt of which is
hereby acknowledged, the parties mutually agree as follows:

     1.  Recitals.  The above recitals are true and correct and are incorporated
         --------                                                               
herein by this reference.

     2.  Grant of Security Interest.  To secure the payment of the Note to the
         --------------------------                                           
Secured Party, the Debtor does hereby grant to the Secured Party a security
interest in and to all inventory now owned or hereafter acquired by Debtor,
including without limitation all parts and accessories, and proceeds therefrom
(the "Collateral").

     3.  Rights Upon Default.  Upon the occurrence of an Event of Default, as
         -------------------                                                 
defined in the Note, the Secured Party shall have the rights and remedies of a
secured party under the Florida Uniform Commercial Code and any and all rights
and remedies available to Secured Party under any other applicable law.

     4.  Perfection.  In order to perfect Secured Party's security interest in
         ----------                                                           
the Collateral, Debtor shall execute and deliver to Secured Party a UCC-1
financing statement which shall be filed with the Florida Secretary of State.
The Debtor shall pay all costs of filing such financing statement.

     5.  Senior Security Interest.  Secured Party's security interest hereunder
         ------------------------                                              
shall be a first lien on the Collateral, senior and prior to any other security
interests that Debtor may grant in the Collateral.

     6.  Notice.  All notices under this Agreement shall be in writing and shall
         ------                                                                 
be deemed to have been given (i) in the case of delivery, when delivered to the
address set forth on the signature page to this Agreement, (ii) in the case of
mailing, on the third business day after deposit in the U.S. Mail, postage
prepaid, certified or registered mail and addressed to the other party at the
<PAGE>
 
address set forth on the signature page to this Agreement; and (iii) in all
other cases when the same has been actually received by the other party.  Either
party may change its address to which said notices are to be sent by the giving
of notice of such change as set forth herein.

     7.  Term.  This Agreement and the rights and privileges granted hereunder
         ----                                                                 
to the Secured Party shall  continue and remain in full force and effect until
the Obligation has been paid in full to the Secured Party.  At such time, this
Agreement, marked "canceled" and the Note, marked "Paid in Full", shall be
returned to Debtor, and the Secured Party shall further execute a termination
statement in regard to any financing statement that is solely related to the
Collateral.

     8.  Governing Law.  This Agreement has been delivered in the State of
         -------------                                                    
Florida and shall be construed in accordance and governed by the laws of
Florida.

     9.  Counterparts.  This Agreement may be executed in several counterparts,
         ------------                                                          
each of which shall be deemed an original and all of which together shall be
deemed on and the same instrument.

     10.  Complete Agreement.  This Agreement constitutes the complete agreement
          ------------------                                                    
between the parties in regard to the matters set forth herein and this Agreement
may not be altered, amended or otherwise modified except by a writing signed by
both parties hereto.

     IN WITNESS WHEREOF, the Debtor and Secured Party have executed this
Agreement as of the date and year first above written.

                                             "Debtor"

                                             CARDIAC CONTROL SYSTEMS, INC.


                                             By: /s/ Alan Rabin
                                                ---------------------------
                                                Alan Rabin, President
                                                3 Commerce Blvd.
                                                Palm Coast, FL  32164

                                             "Secured Party"

                                             /s/ Bart C. Gutekunst
                                             -------------------------------   
                                             Bart C. Gutekunst
                                             10 Timothy Road
                                             Weston, CT  06883
<PAGE>
 
                                                                   EXHIBIT 10.21

                            SECURED PROMISSORY NOTE



$108,246.64                                                  October 28, 1996
                                                          Palm Coast, Florida


     FOR VALUE RECEIVED, the undersigned, Cardiac Control Systems, Inc., a
Delaware corporation (the "Maker"), hereby promises to pay to Bart C. Gutekunst,
an individual (the "Payee"), at Payee's principal place of business or such
other place as Payee may from time to time designate in writing, the principal
amount of One Hundred Eight Thousand Two Hundred Forty-Six Dollars and 64/100
($US108,246.64), together with interest on unpaid principal from time to time
outstanding computed from the date of this Note, at the rate provided herein.
The Maker may prepay, at any time and from time to time, without penalty, all or
a portion of said amount.

     1.  Commencing on the date of this Note, the unpaid principal balance from
time to time outstanding hereunder shall bear interest at the rate of ten
percent (10%) per annum, which interest shall accrue to February 15, 1996 (the
"Maturity Date"), at which time the entire amount of unpaid principal and any
accrued but unpaid interest shall be paid in full.

     2.  Notwithstanding the provisions of Section 1 of this Note, from and
after the date of an Event of Default (defined below), the outstanding principal
and accrued and unpaid interest shall together be deemed outstanding principal
and the interest on such principal shall be computed at the rate of three
percent (3%) per month, which interest shall be payable monthly commencing on
the first day of the calendar month following the date of an Event of Default,
and continuing thereafter until the outstanding principal balance and any
accrued and unpaid interest is paid in full.

     3.  The entire unpaid amount of this Note, inclusive of principal and
interest, shall become immediately due and payable upon the occurrence of an
Event of Default, as defined below.  The term "Event of Default", as used
herein, shall mean the occurrence and continuation of any one or more of the
following events:  (a)  the failure of Maker to pay in full this Note on the
Maturity Date;  (b)  the adjudication of Maker as a bankrupt or insolvent, or an
assignment by Maker for the benefit of creditors; (c)  the voluntary, or
involuntary, appointment of a receiver, trustee or similar officer for Maker or
for any substantial part of its property or business, and which appointment, if
involuntary, shall have continued for a period of ninety (90) days;  (d)  the
voluntary, or involuntary, institution of bankruptcy, insolvency,
reorganization, arrangement, dissolution, liquidation or similar proceeding
relating to the Company, and which, if involuntary, shall have continued for as
period of ninety (90) days.

     This Note shall be governed by and construed in accordance with the laws of
the State of Florida.
<PAGE>
 
     This payment of this Note is secured by a security agreement and UCC-1
financing statement, of even date herewith, on certain personal property of
Maker and being used in the business of Maker.


                                             CARDIAC CONTROL SYSTEMS, INC.


                                             By: /s/ Alan Rabin
                                                ---------------------------
                                               Alan Rabin, President