<PAGE>
 
                                                                    EXHIBIT 10.4


Warrant No. FS-2


                                               Warrant to Purchase 83,329 Shares



                            SHARE PURCHASE WARRANT

             To Purchase Shares of Common Stock (par value $0.001)

                                      of

                      Nitinol Medical Technologies, Inc.
                            (Delaware corporation)



                           Expires February 14, 2001
<PAGE>
 
Warrant No.  FS-2

NEITHER THIS WARRANT NOR THE SHARES ISSUABLE UPON EXERCISE HEREOF MAY BE
TRANSFERRED EXCEPT IN A TRANSACTION REGISTERED UNDER THE SECURITIES ACT OF 1933,
AS AMENDED, OR WHICH IS EXEMPT FROM THE REGISTRATION REQUIREMENTS OF THAT ACT.


           VOID AFTER 5:00 P.M. NEW YORK TIME, ON February 14, 2001

                      Nitinol Medical Technologies, Inc.

                  Warrant to Purchase Shares of Common Stock


                                                                   83,329 Shares

     THIS CERTIFIES that, for good and valuable consideration received, Fletcher
Spaght, Inc. (the "Holder"), is entitled to subscribe for and purchase from
                   ------                                                  
Nitinol Medical Technologies, Inc., a Delaware corporation (the "Company"), upon
                                                                 -------        
the terms and conditions set forth herein, at any time or from time to time
until 5:00 P.M. New York City time on February 14, 2001 (the "Expiration Date"),
                                                              ---------------   
all or any portion of 83,329 Shares of common stock of the Company, par value
$0.001 per share, subject to adjustment as provided herein (the "Warrant
                                                                 -------
Shares"), at a price of $1.13 per share, subject to adjustment as provided
------
herein (the "Exercise Price"). This Warrant shall not be redeemable by the
             --------------
Company. The term "Shares" as used herein shall mean the Company's Shares of
Common Stock, par value $0.001 per share. This Warrant may be sold, transferred,
assigned or hypothecated at any time and the term the "Holder" as used herein
                                                       ------                
shall include any transferee to whom this Warrant has been transferred.

     1.   Method of Exercise.  This Warrant may be exercised at any time prior
          ------------------                                                  
to the Expiration Date, as to the whole or any lesser number of Warrant Shares,
by the surrender of this Warrant (with the election at the end hereof duly
executed) to the Company at its office at 27 Wormwood Street, Boston, MA 02210
or at such other place as may be designated in writing by the Company, together
with a certified or bank cashier's check payable to the order of the Company in
an amount equal to the Exercise Price multiplied by the number of Warrant Shares
for which this Warrant is being exercised.  To the extent that the holders of
options to purchase Shares granted pursuant to the Company's 1994 Stock Option
Incentive Plan are accorded a "net exercise" right with respect to such options
whereby the Company will withhold from the Shares that would otherwise be issued
upon exercise of such options that number of Shares having a market value equal
to the option exercise price, the Company will grant such "net exercise" right
to the Holder with respect to the exercise of this Warrant for the Warrant
Shares.

<PAGE>
 
     2.   Issuance of Certificates.  Upon each exercise of the Holder's rights
          ------------------------                                            
to purchase Warrant Shares, the Holder shall, as of the close of business on
such day, be deemed to be the holder of record of the Warrant Shares issuable
upon such exercise, notwithstanding that the transfer books of the Company shall
then be closed or certificates representing such Warrant Shares shall not then
have been actually delivered to the Holder.  As soon as practicable after each
such exercise of this Warrant, the Company shall issue and deliver to the Holder
a certificate or certificates for the Warrant Shares issuable upon such
exercise, registered in the name of the Holder or its designee. If this Warrant
should be exercised in part only, upon surrender of this Warrant for
cancellation, the Company shall execute and deliver a new Warrant evidencing the
right of the Holder to purchase the balance of the Warrant Shares (or portions
thereof) subject to purchase hereunder.

     3.   Recording of Transfer.  Any warrants issued upon the transfer or
          ---------------------                                           
exercise in part of this Warrant shall be numbered and shall be registered in a
Warrant Register as they are issued.  The Company shall be entitled to treat the
registered holder of any Warrant on the Warrant Register as the owner in fact
thereof for all purposes and shall not be bound to recognize any equitable or
other claim to or interest in such Warrant on the part of any other person, and
shall not be liable for any registration or transfer of warrants which are
registered or to be registered in the name of a fiduciary or the nominee of a
fiduciary unless made with the actual knowledge that a fiduciary or nominee is
committing a breach of trust in requesting such registration or transfer, or
with the knowledge of such facts that its participation therein amounts to bad
faith.  This Warrant shall be transferable only on the books of the Company upon
delivery thereof duly endorsed by the Holder or by his or its duly authorized
attorney or representative, or accompanied by proper evidence of succession,
assignment or authority to transfer. In all cases of transfer by an attorney,
executor, administrator, guardian or other legal representative, duly
authenticated evidence of his or its authority shall be produced. Upon any
registration of transfer, the Company shall deliver a new warrant or warrants to
the person entitled thereto.  This Warrant may be exchanged, at the option of
the Holder hereof, for another warrant, or other warrants of different
denominations, of like tenor and representing in the aggregate the right to
purchase a like number of Warrant Shares (or portions thereof), upon surrender
to the Company or its duly authorized agent.  Notwithstanding the foregoing, the
Company shall have no obligation to cause this Warrant to be transferred on its
books to any person if counsel to the Company reasonably requests a legal
opinion that such transfer does not violate the provisions of the Securities Act
of 1933, as amended (the "Act"), and the rules and regulations thereunder,
                          ---                                             
unless such opinion is delivered.

     4.   Reservation of Shares.  The Company shall at all times reserve and
          ---------------------                                             
keep available out of its authorized and unissued Shares, solely for the purpose
of providing for the exercise of the warrants, such number of shares of Shares
as shall, from time to time, be sufficient therefor.  The Company covenants that
all shares of Shares issuable 

                                      -2-
<PAGE>
 
upon exercise of this Warrant, upon receipt by the Company of the full payment
therefor, shall be validly issued, fully paid, nonassessable and free of
preemptive rights.

     5.   Exercise Price Adjustments.  Subject to the provisions of this Section
          --------------------------                                            
5, the Exercise Price in effect from time to time shall be subject to
adjustment, as follows:

          (a)  In case the Company shall at any time after the date hereof (i)
declare a dividend or make a distribution on the outstanding Shares payable in
shares of its capital stock or securities convertible into or exchangeable for
capital stock, (ii) subdivide the outstanding Shares, (iii) combine the
outstanding Shares into a smaller number of shares, or (iv) issue any shares by
reclassification of the Shares (other than a change in par value, or from par
value to no par value, or from no par value to par value), then in each case,
                                                           ----              
the Exercise Price in effect, and the number of Shares issuable upon exercise of
the warrants outstanding, at the time of the record date for such dividend or at
the effective date of such subdivision, combination or reclassification, shall
be proportionately adjusted so that the holders of the warrants after such time
shall be entitled to receive upon exercise of the warrant the aggregate number
and kind of shares which, if such warrants had been exercised immediately prior
to such time, such holders would have owned upon such exercise and immediately
thereafter been entitled to receive by virtue of such dividend, subdivision,
combination or reclassification.  Such adjustment shall be made successively
whenever any event listed above shall occur.

          (b)  In case the Company shall distribute to all holders of Shares
(including any such distribution made to the stockholders of the Company in
connection with a consolidation or merger in which the Company is the surviving
or continuing corporation) evidences of its indebtedness, cash, or assets (other
than distributions and dividends payable as contemplated by Section 5(a) above),
or rights, options, or warrants to subscribe for or purchase Shares or
securities convertible into or exchangeable for Shares, then, in each case, the
Exercise Price shall be adjusted by multiplying the Exercise Price in effect
immediately prior to the record date for the determination of stockholders
entitled to receive such distribution by a fraction, the numerator of which
shall be the Current Market Price (as determined pursuant to Section 5(e)
hereof) per Share on such record date, less the fair market value (as determined
in good faith by the board of directors of the Company, whose determination
shall be conclusive absent manifest error) of the portion of the evidences of
indebtedness or assets so to be distributed, or of such rights, options, or
warrants or convertible or exchangeable securities, or the amount of such cash,
applicable to one share, and the denominator of which shall be such Current
Market Price per Share.  Such adjustment shall become effective at the close of
business on such record date.

          (c)  Whenever there shall be an adjustment as provided in this Section
5, the Company shall within 15 days thereafter cause written notice thereof to
be sent by registered mail, postage prepaid, to the Holder, at its address as it
shall appear in the Warrant Register, which notice shall be accompanied by an
officer's certificate setting 

                                      -3-
<PAGE>
 
forth the number of Warrant Shares issuable hereunder and the exercise price
thereof after such adjustment and setting forth a brief statement of the facts
requiring such adjustment and the computation thereof, which officer's
certificate shall be conclusive evidence of the correctness of any such
adjustment absent manifest error.

          (d)  The Company shall not be required to issue fractions of Shares or
other shares of the Company upon the exercise of this Warrant.  If any fraction
of a share would be issuable upon the exercise of this Warrant (or specified
portions thereof), the Company may issue a whole share in lieu of such fraction
or the Company may purchase such fraction for an amount in cash equal to the
same fraction of the Current Market Price of such Shares on the date of exercise
of this Warrant.

          (e)  The Current Market Price per Share on any date shall be deemed to
be the average of the daily closing prices for the thirty (30) consecutive
trading days immediately preceding the date in question.  The closing price for
each day shall be the last reported sales price regular way or, in case no such
reported sale takes place on such day, the closing bid price regular way, in
either case on the principal national securities exchange on which the Common
Stock is listed or admitted to trading or, if the Common Stock is not listed or
admitted to trading on any national securities exchange, the highest reported
bid price for the Common Stock as furnished by the National Association of
Securities Dealers, Inc. through Nasdaq or a similar organization if Nasdaq is
no longer reporting such information.  If on any such date the Common Stock is
not listed or admitted to trading on any national securities exchange and is not
quoted by Nasdaq or any similar organization, the fair value of a share of
Common Stock on such date, as determined in good faith by the Board of Directors
of the Company, whose determination shall be conclusive absent manifest error,
shall be used.

          (f)  No adjustment in the Exercise Price shall be required if such
adjustment is less than $0.05; provided, however, that any adjustments which by
reason of this Section 5 are not required to be made shall be carried forward
and taken into account in any subsequent adjustment.  All calculations under
this Section 5 shall be made to the nearest cent or to the nearest thousandth of
a share, as the case may be.

          (g)  Upon each adjustment of the Exercise Price as a result of the
calculations made in this Section 5, the warrants shall thereafter evidence the
right to purchase, at the adjusted Exercise Price, that number of Shares
(calculated to the nearest hundredth) obtained by dividing (i) the product
obtained by multiplying the number of Shares purchasable upon exercise of the
warrants prior to adjustment of the number of Shares by the Exercise Price in
effect prior to adjustment of the Exercise Price by (ii) the Exercise Price in
effect after such adjustment of the Exercise Price.

     6.   (a)  Consolidations and Mergers.  In case of any consolidation with or
               --------------------------                                       
merger of the Company with or into another corporation (other than a merger or
consolidation in which the Company is the surviving or continuing corporation
and 

                                      -4-
<PAGE>
 
which does not result in any reclassification of the outstanding Shares or the
conversion of such outstanding Shares into shares of other stock or other
securities or property), or in case of any sale, lease or conveyance to another
corporation of the property and assets of any nature of the Company as an
entirety or substantially as an entirety (such actions being hereinafter
collectively referred to as "Reorganizations"), there shall thereafter be
                             ---------------                             
deliverable upon exercise of this Warrant (in lieu of the number of Shares
theretofore deliverable) the kind and amount of shares of stock or other
securities, cash or other property which would otherwise have been deliverable
to a holder of the number of Shares upon the exercise of this Warrant upon such
Reorganization if this Warrant had been exercised in full immediately prior to
such Reorganization.  In case of any Reorganization, appropriate adjustment, as
determined in good faith by the Board of Directors of the Company, shall be made
in the application of the provisions herein set forth with respect to the rights
and interests of the Holder so that the provisions set forth herein shall
thereafter be applicable, as nearly as possible, in relation to any shares or
other property thereafter deliverable upon exercise of this Warrant.  Any such
adjustment shall be made by and set forth in a supplemental agreement between
the Company, or any successor thereto, and the Holder and shall for all purposes
hereof conclusively be deemed to be an appropriate adjustment.  The Company
shall not effect any such Reorganization unless upon or prior to the
consummation thereof the successor corporation, or if the Company shall be the
surviving corporation in any such Reorganization and is not the issuer of the
shares of stock or other securities or property to be delivered to holders of
Shares outstanding at the effective time thereof, then such issuer, shall assume
by written instrument the obligation to deliver to the Holder such shares of
stock, securities, cash or other property as the Holder shall be entitled to
purchase in accordance with the foregoing provisions.

          (b)  In case of any reclassification or change of the Shares issuable
upon exercise of this Warrant (other than a change in par value or from no par
value to a specified par value, or as a result of a subdivision or combination,
but including any change in the shares into two or more classes or series of
shares), or in case of any consolidation or merger of another corporation into
the Company in which the Company is the continuing corporation and in which
there is a reclassification or change (including a change to the right to
receive cash or other property) of the Shares (other than a change in par value,
or from no par value to a specified par value, or as a result of a subdivision
or combination, but including any change in the shares into two or more classes
or series of shares), the Holder shall have the right thereafter to receive upon
exercise of this Warrant solely the kind and amount of shares of stock and other
securities, property, cash or any combination thereof receivable upon such
reclassification, change, consolidation or merger by a holder of the number of
Shares for which this Warrant might have been exercised immediately prior to
such reclassification, change, consolidation or merger.  Thereafter, appropriate
provision shall be made for adjustments which shall be as nearly equivalent as
practicable to the adjustments in Section 5.

                                      -5-
<PAGE>
 
          (c)  The above provisions of this Section 6 shall similarly apply to
successive reclassifications and changes of Shares and to successive
consolidations, mergers, sales, leases, or conveyances.

     7.   Notice of Certain Events.  In case at any time any of the following
          ------------------------                                           
occur:

          (a)  The Company shall take a record of the holders of its Shares for
the purpose of entitling them to receive a dividend or distribution payable
otherwise than in cash, or a cash dividend or distribution payable otherwise
than out of current or retained earnings, as indicated by the accounting
treatment of such dividend or distribution on the books of the Company; or

          (b)  The Company shall offer to all the holders of its Shares any
additional shares of capital stock of the Company or securities convertible into
or exchangeable for shares of capital stock of the Company, or any option, right
or warrant to subscribe therefor; or

          (c)  The Company shall take any action to effect any reclassification
or change of outstanding Shares or any consolidation, merger, sale, lease or
conveyance of property, described in Section 6; or

          (d)  The Company shall take any action to effect any liquidation,
dissolution or winding-up of the Company or a sale of all or substantially all
of its property, assets and business;

then, and in any one or more of such cases, the Company shall give written
----                                                                      
notice thereof, by registered mail, postage prepaid, to the Holder at the
Holder's address as it shall appear in the Warrant Register, mailed at least
fifteen (15) days prior to (i) the date as of which the holders of record of
Shares to be entitled to receive any such dividend, distribution, rights,
warrants or other securities are to be determined, (ii) the date on which any
such offer to holders of Shares is made, or (iii) the date on which any such
reclassification, change of outstanding Shares, consolidation, merger, sale,
lease, conveyance of property, liquidation, dissolution or winding-up is
expected to become effective and the date as of which it is expected that
holders of record of Shares shall be entitled to exchange their shares for
securities or other property, if any, deliverable upon such reclassification,
change of outstanding shares, consolidation, merger, sale, lease, conveyance of
property, liquidation, dissolution or winding-up.  Nothing herein shall allow a
Holder to delay or prevent any of the foregoing actions.

     8.   Registration Rights.  The holders of any Warrants or Warrant Shares
          -------------------                                                
shall have, in respect of the shares of Common Stock underlying the Warrants or
the Warrant Shares, as the case may be, those certain registration rights as are
set forth in the Registration Rights Agreement, dated as of the date hereof,
between the Company and the Holder, a copy of which is attached hereto.

                                      -6-
<PAGE>
 
     9.   Taxes.  The issuance of any shares or other securities upon the
          -----                                                          
exercise of this Warrant and the delivery of certificates or other instruments
representing such shares or other securities shall be made without charge to the
Holder for any tax or other charge in respect of such issuance.  The Company
shall not, however, be required to pay any tax which may be payable in respect
of any transfer involved in the issue and delivery of any certificate in a name
other than that of the Holder (except for any tax that is payable in respect of
any such transfer and any related exercise of this Warrant and that would be
payable pursuant to the first sentence of this Section 9 were such certificate
to be issued in the name of the Holder) and the Company shall not be required to
issue or deliver any such certificate unless and until the person or persons
requesting the issue thereof shall have paid to the Company the amount of such
tax or shall have established to the satisfaction of the Company that such tax
has been paid.

     10.  Legend.  Unless registered pursuant to the provisions of Section 8
          ------                                                            
hereof, the certificate or certificates evidencing the Warrant Shares, shall
bear the following legend:

                    "THE SECURITIES REPRESENTED BY THIS CERTIFICATE
               HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
               1933, AS AMENDED (THE "ACT"), OR STATE SECURITIES LAWS,
               BUT HAVE BEEN ISSUED OR TRANSFERRED PURSUANT TO AN
               EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE
               ACT. NO DISTRIBUTION, SALE, OFFER FOR SALE, TRANSFER,
               DELIVERY, PLEDGE, OR OTHER DISPOSITION OF THESE
               SECURITIES MAY BE EFFECTED EXCEPT IN COMPLIANCE WITH
               THE ACT, ANY APPLICABLE STATE LAWS, AND THE RULES AND
               REGULATIONS OF THE SECURITIES AND EXCHANGE COMMISSION
               AND STATE AGENCIES PROMULGATED THEREUNDER."


     11.  Replacement of Warrants.  Upon receipt of evidence satisfactory to the
          -----------------------                                               
Company of the loss, theft, destruction or mutilation of any Warrant (and upon
surrender of any Warrant if mutilated), and upon reimbursement of the Company's
reasonable incidental expenses and execution of a reasonable lost security
indemnification agreement, the Company shall execute and deliver to the Holder
thereof a new Warrant of like date, tenor and denomination.

     12.  No Rights as Stockholder.  The Holder of any Warrant shall not have,
          ------------------------                                            
solely on account of such status, any rights of a stockholder of the Company,
either at 

                                      -7-
<PAGE>
 
law or in equity, or to any notice of meetings of stockholders or of any other
proceedings of the Company, except as provided in this Warrant.

     13.  Notices.  All notices, requests, consents and other communications
          -------                                                           
hereunder shall be in writing and shall be deemed to have been duly made when
delivered, or mailed by registered or certified mail, return receipt requested:

          (a)  If to the registered Holder of this Warrant, to the address of
such Holder as shown on the books of the Company; or

          (b)  If to the Company, to the address set forth on the first page of
this Warrant or to such other address as the Company may designate by notice to
the Holder.

     14.  Successors.  All the covenants, agreements, representations and
          ----------                                                     
warranties contained in this Warrant shall bind the parties hereto and their
respective heirs, executors, administrators, distributees, successors and
assigns.

     15.  Headings.  The Article and Section headings in this Warrant are
          --------                                                       
inserted for purposes of convenience only and shall have no substantive effect.

     16.  Governing Law.  This Warrant shall be constrained in accordance with
          -------------                                                       
the laws of the State of Delaware applicable to contracts made and performed
within such State, without regard to principles of conflicts of law.

     17.  Modification of Amendment.  This Warrant shall not otherwise be
          -------------------------                                      
modified, supplemented or amended in any respect unless such modification,
supplement or amendment is in writing and signed by the Company and the Holder
of this Warrant and Holders of any portion of the Warrant subsequently assigned
or transferred in accordance with the terms of this Warrant.

                                      -8-
<PAGE>
 
     IN WITNESS WHEREOF, the undersigned has executed this instrument as of the
date set forth below.



Dated:  July 1, 1998                NITINOL MEDICAL TECHNOLOGIES, INC.


                                    By: /s/ Thomas Tully
                                       -------------------------------------
                                       Name:  Thomas Tully
                                       Title: President and Chief Executive
                                              Officer

                                      -9-
<PAGE>
 
                              FORM OF ASSIGNMENT


     (To be executed by the registered holder if such holder desires to transfer
the attached Warrant.)

     FOR VALUE RECEIVED, ______________________ hereby sells, assigns, and
transfers unto _________________, having an address at ______________________,
the attached Warrant to the extent of the right to purchase ___________ Shares
of Common Stock, $0.001 par value per share, of Nitinol Medical Technologies,
Inc. (the "Company"), together with all right, title, and interest therein, and
           -------                            
does hereby irrevocably constitute and appoint _______________ as attorney to
transfer such Warrant on the books of the Company, with full power of
substitution.


Dated:  _______________, 199___

                              ___________________________________
                              Print name of holder of Warrant


                              By: _______________________________
                              Name:
                              Title:



                                    NOTICE

     The signature on the foregoing Assignment must correspond to the name as
written upon the face of this Warrant in every particular, without alteration or
enlargement or any change whatsoever.

                                      -10-
<PAGE>
 
To:


     The undersigned hereby exercises its rights to purchase _________ Warrant
Shares covered by the within Warrant and tenders payment herewith in the amount
of $_____________ in accordance with the terms thereof, and requests that
certificates for such securities be issued in the name of, and delivered to:



                   (Print Name, Address and Social Security
                         or Tax Identification Number)

and, if such number of Warrant Shares shall not be all the Warrant Shares
covered by the within Warrant, that a new Warrant for the balance of the Warrant
Shares covered by the within Warrant be registered in the name of, and delivered
to, the undersigned at the address stated below.


Dated:____________________         Name:____________________________________
                                                      (Print)



                                   _________________________________________
                                                      (Signature)
                                   (Signature must conform to the name of the
                                   Warrant Holder specified on the face of the
                                   Warrant)

Address:

                                      -11-