<PAGE>
     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JULY   , 1996
 
                                                      REGISTRATION NO. 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
 
                            ------------------------
 
                                    FORM S-8
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
 
                            ------------------------
 
                               HEARTSTREAM, INC.
             (Exact name of Registrant as specified in its charter)
 
<TABLE>
<S>                     <C>                           <C>
       DELAWARE                                                  91-1577477
      (State of                                        (I.R.S. Employer Identification
    incorporation)                                                  No.)
</TABLE>
 
                         2401 Fourth Avenue, Suite 300
                           Seattle, Washington 98121
   (Address, including Zip code, of Registrant's principal executive offices)
 
                    1993 EMPLOYEE AND CONSULTANT STOCK PLAN
                       1995 EMPLOYEE STOCK PURCHASE PLAN
                           1995 DIRECTOR OPTION PLAN
 
                            (Full title of the plan)
 
                               Heartstream, Inc.
                         2401 Fourth Avenue, Suite 300
                           Seattle, Washington 98121
                                 (206) 443-7630
(Name, address, and telephone number, including area code, of agent for service)
 
                            ------------------------
 
                                   COPIES TO:
 
                             Timothy Stevens, Esq.
                        Wilson Sonsini Goodrich & Rosati
                            Professional Corporation
                               650 Page Mill Road
                            Palo Alto, CA 94304-1050
                                 (415) 493-9300
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>
                        CALCULATION OF REGISTRATION FEE
 
<TABLE>
<CAPTION>
                                                                PROPOSED         PROPOSED
                                                                 MAXIMUM          MAXIMUM       AMOUNT OF
        TITLE OF SECURITIES               AMOUNT TO BE       OFFERING PRICE      AGGREGATE     REGISTRATION
        TO BE REGISTERED (1)               REGISTERED           PER SHARE     OFFERING PRICE       FEE
<S>                                   <C>                    <C>              <C>              <C>
1993 Employee and Consultant Stock
 Plan
Common Stock, $.001 par value.......  1,382,637 shares (2)     $ 4.18 (3)     $5,779,423 (4)      $1,993
Common Stock, $.001 par value.......   797,737 shares (5)      $ 9.25 (6)     $7,379,067 (7)      $2,545
1995 Director Option Plan
Common Stock, $.001 par value.......    60,000 shares (8)      $13.00 (9)     $ 780,000 (10)      $ 269
Common Stock, $.001 par value.......   90,000 shares (11)      $ 9.25 (6)      $ 832,500 (7)      $ 288
1995 Employee Stock Purchase Plan
Common Stock, $.001 par value.......   250,000 shares (12)     $ 7.87 (13)    $1,967,500 (14)     $ 679
</TABLE>
 
 (1)In  addition, pursuant to Rule 416(c) under  the Securities Act of 1933 (the
    "Act"), this Registration Statement also  covers an indeterminate amount  of
    interests  to  be offered  or sold  pursuant to  the employee  benefit plans
    described herein.
 
 (2)For the sole  purpose of  calculating the  registration fee,  the number  of
    shares  to be registered  under this Registration  Statement has been broken
    down into  five subtotals.  This subtotal  represents the  number of  shares
    issuable  upon exercise of currently  outstanding options (options that have
    been granted as of the date of this Registration Statement) issued under the
    1993 Employee and Consultant Stock Plan.
 
 (3)Calculated in  accordance with  Rule 457(h)  under the  Act solely  for  the
    purpose  of calculating the total registration fee. Calculation based on the
    weighted average exercise price (rounded to  the nearest cent) at which  the
    options outstanding whose exercise will result in the issuance of the shares
    being registered may be exercised.
 
 (4)Calculated  in  accordance  with Rule  457(h)  under  the Act  based  on the
    aggregate exercise price of all  currently outstanding options as  described
    in note 2 above.
 
 (5)This  subtotal represents  the number  of shares  issuable upon  exercise of
    options that are available  for grant, but have  not yet been granted  under
    the 1993 Employee and Consultant Stock Plan.
 
 (6)Estimated  in  accordance with  Rule  457(h) under  the  Act solely  for the
    purpose of calculating the total registration fee. The calculation is  based
    upon  the  closing price  of  the Common  Stock  as reported  on  the Nasdaq
    National Market on July 15, 1996 because  the price at which the options  to
    be granted in the future may be exercised is not currently determinable.
 
 (7)Calculated  in  accordance  with Rule  457(h)  under  the Act  based  on the
    aggregate exercise price for options available for grant.
 
 (8)This subtotal  represents the  number of  shares issuable  upon exercise  of
    currently outstanding options (options that have been granted as of the date
    of this Registration Statement) issued under the 1995 Director Option Plan.
 
 (9)Calculated  in  accordance with  Rule 457(h)  under the  Act solely  for the
    purpose of calculating the total registration fee. The calculation is  based
    upon  the  closing price  of  the Common  Stock  as reported  on  the Nasdaq
    National Market on January 31, 1996.
 
(10)Calculated in  accordance  with Rule  457(h)  under  the Act  based  on  the
    aggregate  exercise price of all  currently outstanding options as described
    in note 8 above.
 
(11)This subtotal  represents the  number of  shares issuable  upon exercise  of
    options  that are available for  grant, but have not  yet been granted under
    the 1995 Director Option Plan.
 
(12)This subtotal represents the number of shares authorized to be issued  under
    the 1995 Employee Stock Purchase Plan.
 
(13)Estimated  in  accordance with  Rule  457(h) under  the  Act solely  for the
    purpose of calculating  the total registration  fee. Calculation based  upon
    85%  (see explanation  in following  sentence) of  the closing  price of the
    Common Stock as  reported on  the Nasdaq National  Market on  July 15,  1996
    because  the price at which  the options to be granted  in the future may be
    exercised is not currently  determinable. The purchase price  of a share  of
    Common  Stock pursuant to the 1995  Employee Stock Purchase Plan, which plan
    is incorporated by  reference herein,  is equal to  85% of  the Fair  Market
    Value  of a share of Common Stock on either the first day or the last day of
    the relevant offering period, whichever is lower.
 
(14)Calculated in  accordance  with Rule  457(h)  under  the Act  based  on  the
    aggregate  exercise price for all options  available as described in note 12
    above.
<PAGE>
                                    PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
 
ITEM 3.  INFORMATION INCORPORATED BY REFERENCE
 
    The following documents and information previously filed with the Securities
and Exchange Commission are hereby incorporated by reference.
 
    (a)The  audited financial statements for  the Registrant's fiscal year ended
       December 31,  1995 contained  in the  Prospectus filed  pursuant to  Rule
424(b)(4) under the Securities Act of 1933 on February 2, 196.
 
    (b)The  Registrant's Quarterly  Report on  Form 10-Q  for the  quarter ended
       March 31, 1996, filed pursuant to Section  13 of the Exchange Act on  May
14, 1996.
 
    (c)The  description of the Common Stock  of the Registrant that is contained
       in the Registration Statement on Form 8-A filed pursuant to Section 12 of
the Exchange Act on December 1, 1995.
 
    (d)All documents filed by the Registrant pursuant to Sections 13(a),  13(c),
       14  and  15(d) of  the  Exchange Act  subsequent  to the  filing  of this
Registration Statement and  prior to  the filing of  a post-effective  amendment
which  indicates that all securities offered have been sold or which deregisters
all securities then  remaining unsold,  shall be  deemed to  be incorporated  by
reference  in the Registration Statement and to be part thereof from the date of
filing of such documents.
 
ITEM 4.  DESCRIPTION OF SECURITIES.
 
    Not applicable.
 
ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.
 
    Certain  members  of  Wilson  Sonsini  Goodrich  and  Rosati,   Professional
Corporation,   beneficially  own   twenty  thousand   (20,000)  shares   of  the
Registrant's Common Stock.
 
ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
    Section 145 of  the General  Corporation Law  of Delaware  provides for  the
indemnification  of  officers, directors  and  other corporate  agents  in terms
sufficiently broad to indemnify such  persons, under certain circumstances,  for
certain liabilities (including reimbursement of expenses incurred) arising under
the Securities Act of 1933 (the "Securities Act").
 
    The  Registrant's  Bylaws provide  that the  Registrant shall  indemnify its
directors and officers and  may indemnify its other  officers and employees  and
other  agents to the fullest extent permitted by law, including circumstances in
which indemnification is otherwise discretionary under Delaware law.
 
    The Registrant has  adopted provisions in  its Certificate of  Incorporation
that eliminate the personal liability of its directors and officers for monetary
damages arising from a breach of their fiduciary duties in certain circumstances
to  the  fullest  extent  permitted  by law  and  authorizes  the  Registrant to
indemnify its directors  and officers to  the fullest extent  permitted by  law.
Such  limitation  of liability  does not  affect  the availability  of equitable
remedies such as injunctive relief or recission.
 
    The Registrant entered  into indemnification agreements  with its  executive
officers  and directors containing provisions which are in some respects broader
that  the  specific   indemnification  provisions  contained   in  the   General
Corporation  Laws of  Delaware. The  indemnification agreements  may require the
Company, among other things,  to indemnify such  officers and directors  against
certain  liabilities that  may arise  by reason  of their  status or  service as
directors or officers (other than liabilities arising from willful misconduct of
a culpable nature). These agreements also indemnify the directors and  executive
officers  for certain expenses (including attorney's fees), judgments, fines and
settlement amounts incurred  as a result  of any proceeding  against them as  to
which they could be indemnified.
 
                                      II-1
<PAGE>
ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.
 
    Not applicable.
 
ITEM 8.  EXHIBITS.
 
<TABLE>
<CAPTION>
EXHIBIT
NUMBER                                                          DOCUMENT
- ------ ---------------------------------------------------------------------------------------------------------------------------
<C>    <S>
    5.1 Opinion of Wilson Sonsini Goodrich & Rosati, Professional Corporation, as to the legality of securities being registered.
  *10.2 1993 Employee and Consultant Stock Plan and form of Stock Option Agreement thereunder.
  *10.3 1995 Director Option Plan and form of Stock Option Agreement thereunder.
  *10.4 1995 Employee Stock Purchase Plan and forms of agreements thereunder.
   23.1 Consent of Ernst & Young LLP, Independent Auditors
   23.2 Consent of Wilson Sonsini Goodrich & Rosati, Professional Corporation (contained in Exhibit 5.1 hereto)
   24.1 Power of Attorney
</TABLE>
 
- ------------------------
*Incorporated  by reference  to exhibits  filed with  the Company's Registration
 Statement on Form S-1  (file no. 33-99908), in  the form declared effective  on
 January 31, 1996.
 
ITEM 9.  UNDERTAKINGS.
 
    (a)The undersigned Registrant hereby undertakes:
 
       (1) To  file, during any period in which  offers or sales are being made,
           post-effective amendment to  this Registration  Statement to  include
    any  material  information  with respect  to  the plan  of  distribution not
    previously disclosed in the Registration Statement or any material change to
    such information in the Registration Statement.
 
       (2) That,  for  the  purpose  of  determining  any  liability  under  the
           Securities Act, each such post-effective amendment shall be deemed to
    be  a new registration statement relating to the securities offered therein,
    and the offering of such securities at  that time shall be deemed to be  the
    initial bona fide offering thereof.
 
       (3) To  remove from registration  by means of  a post-effective amendment
           any of the  securities being  registered which remain  unsold at  the
    termination of the offering.
 
    (b)The  undersigned  Registrant  hereby  undertakes  that,  for  purposes of
       determining any liability under the  Securities Act of 1933, each  filing
of  the Registrant's annual report pursuant to Section 13(a) or Section 15(d) of
the Securities Exchange Act  of 1934 (and, where  applicable, each filing of  an
employee  benefit  plan's  annual  report  pursuant  to  Section  15(d)  of  the
Securities Exchange  Act of  1934)  that is  incorporated  by reference  in  the
Registration  Statement  shall  be deemed  to  be a  new  registration statement
relating to the securities therein, and the offering of such securities at  that
time shall be deemed to be an initial bona fide offering thereof.
 
    (c)Insofar  as indemnification for liabilities  arising under the Securities
       Act of  1933 may  be  permitted to  directors, officers  and  controlling
persons  of the Registrant  pursuant to the  foregoing provisions, or otherwise,
the Registrant  has been  advised that  in  the opinion  of the  Securities  and
Exchange  Commission such indemnification is  against public policy as expressed
in the Securities  Act and  is, therefore, unenforceable.  In the  event that  a
claim  for indemnification against  such liabilities (other  than the payment by
the  Registrant  of  expenses  incurred  or  paid  by  a  director,  officer  or
controlling  person of the  Registrant in the successful  defense of any action,
suit or proceeding) is
 
                                      II-2
<PAGE>
asserted by such director, officer, or controlling person in connection with the
securities being registered, the Registrant will,  unless in the opinion of  its
counsel  the matter has been settled by controlling precedent, submit to a court
of appropriate jurisdiction the question  whether such indemnification by it  is
against  public policy as expressed in the Act and will be governed by the final
adjudication of such issued.
 
                                      II-3
<PAGE>
                                   SIGNATURES
 
    Pursuant  to the requirements of the  Securities Act of 1933, the Registrant
certifies that it has  reasonable grounds to  believe that it  meets all of  the
requirements  for  filing on  Form  S-8 and  has  duly caused  this Registration
Statement to  be  signed  on  its behalf  by  the  undersigned,  thereunto  duly
authorized, in the City of Seattle, State of Washington, on July 22, 1996.
 
                                          HEARTSTREAM, INC.
 
                                                      /s/ ALAN J. LEVY
                                                           By:
                                          --------------------------------------
                                                        Alan J. Levy
                                                President and Chief Executive
                                                         Officer
 
                               POWER OF ATTORNEY
 
    KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Alan J. Levy and Gary Onn, jointly and severally,
as  his or her attorney-in-fact, each with the power of substitution, for him or
her in  any and  all capacities,  to sign  any amendments  to this  Registration
Statement  on Form S-8,  and to file  the same, with  exhibits thereto and other
documents in connection therewith, with the Securities and Exchange  Commission,
hereby  ratifying and confirming all that  the said attorneys-in-fact, or his or
her substitute or substitutes, may do or cause to be done by virtue hereof.
 
    Pursuant  to  the  requirements  of   the  Securities  Act  of  1933,   this
Registration  Statement  has  been  signed  by  the  following  persons  in  the
capacities and on the date indicated.
 
<TABLE>
<CAPTION>
                  SIGNATURE                                        TITLE                            DATE
- ---------------------------------------------  ---------------------------------------------  ----------------
 
<C>                                            <S>                                            <C>
              /s/ ALAN J. LEVY                 President, Chief Executive Officer and         July 22, 1996
     -----------------------------------        Director* (Principal Executive Officer)
                Alan J. Levy
 
                /s/ GARY ONN                   Director of Finance and Administration         July 22, 1996
     -----------------------------------        (Principal Financial and Accounting Officer)
                  Gary Onn
 
          /s/ MICHAEL J. LEVINTHAL             Director*                                      July 18, 1996
     -----------------------------------
            Michael J. Levinthal
 
             /s/ ELLEN M. FEENEY               Director*                                      July 19, 1996
     -----------------------------------
               Ellen M. Feeney
 
            /s/ FRANK M. FISCHER               Director*                                      July 20, 1996
     -----------------------------------
              Frank M. Fischer
 
             /s/ WENDE S. HUTTON               Director*                                      July 18, 1996
     -----------------------------------
               Wende S. Hutton
 
             /s/ MARK B. KNUDSON               Director*                                      July 19, 1996
     -----------------------------------
               Mark B. Knudson
 
             /s/ KURT C. WHEELER               Director*                                      July 18, 1996
     -----------------------------------
               Kurt C. Wheeler
</TABLE>
 
- ------------------------
* The employee  benefit plans  being registered  pursuant to  this  Registration
  Statement  are  subject to  administration by  the Board  of Directors  of the
  Registrant. Option grants under  the 1995 Director  Option Plan, however,  are
  automatic.
 
                                      II-4
<PAGE>
                               INDEX TO EXHIBITS
 
<TABLE>
<CAPTION>
  EXHIBIT                                              DESCRIPTION                                               PAGE
- -----------  ------------------------------------------------------------------------------------------------  ---------
<C>          <S>                                                                                               <C>
        5.1  Opinion of Wilson Sonsini Goodrich & Rosati, Professional Corporation, as to the legality of
              securities being registered....................................................................
      *10.2  1993 Employee and Consultant Stock Plan and form of Stock Option Agreement thereunder.
      *10.3  1995 Director Option Plan and form of Stock Option Agreement thereunder.
      *10.4  1995 Employee Stock Purchase Plan and forms of agreements under.
       23.1  Consent of Ernst & Young, LLP Independent Auditors..............................................
       23.2  Consent of Wilson Sonsini Goodrich & Rosati, Professional Corporation (contained in Exhibit 5.1
              hereto)........................................................................................
       24.1  Power of Attorney (See Page II-4)...............................................................
</TABLE>
 
- ------------------------
*Incorporated  by reference  to exhibits  filed with  the Company's Registration
 Statement on Form S-1  (file no. 33-99908), in  the form declared effective  on
 January 31, 1996.
[{"type": "S-8", "sequence": "1", "description": "S-8", "secsgml_size_bytes": 21418}]
{"company-data": {"conformed-name": "HEARTSTREAM INC/DE", "cik": "0001004313", "assigned-sic": "3845", "irs-number": "911577477", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-08637", "film-number": "96597848"}, "business-address": {"street1": "2401 FOURTH AVENUE", "street2": "STE 300", "city": "SEATTLE", "state": "WA", "zip": "98121", "phone": "2064437630"}, "mail-address": {"street1": "2401 4TH AVENUE STE 300", "city": "SEATTLE", "state": "WA", "zip": "98121"}}
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JULY   , 1996
 
                                                      REGISTRATION NO. 333-
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
 
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
 
                            ------------------------
 
                                    FORM S-8
                             REGISTRATION STATEMENT
                                     UNDER
                           THE SECURITIES ACT OF 1933
 
                            ------------------------
 
                               HEARTSTREAM, INC.
             (Exact name of Registrant as specified in its charter)
DELAWARE                                                  91-1577477
      (State of                                        (I.R.S. Employer Identification
    incorporation)                                                  No.)
2401 Fourth Avenue, Suite 300
                           Seattle, Washington 98121
   (Address, including Zip code, of Registrant's principal executive offices)
 
                    1993 EMPLOYEE AND CONSULTANT STOCK PLAN
                       1995 EMPLOYEE STOCK PURCHASE PLAN
                           1995 DIRECTOR OPTION PLAN
 
                            (Full title of the plan)
 
                               Heartstream, Inc.
                         2401 Fourth Avenue, Suite 300
                           Seattle, Washington 98121
                                 (206) 443-7630
(Name, address, and telephone number, including area code, of agent for service)
 
                            ------------------------
 
                                   COPIES TO:
 
                             Timothy Stevens, Esq.
                        Wilson Sonsini Goodrich & Rosati
                            Professional Corporation
                               650 Page Mill Road
                            Palo Alto, CA 94304-1050
                                 (415) 493-9300
 
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
CALCULATION OF REGISTRATION FEE
PROPOSED         PROPOSED
                                                                 MAXIMUM          MAXIMUM       AMOUNT OF
        TITLE OF SECURITIES               AMOUNT TO BE       OFFERING PRICE      AGGREGATE     REGISTRATION
        TO BE REGISTERED (1)               REGISTERED           PER SHARE     OFFERING PRICE       FEE
1993 Employee and Consultant Stock
 Plan
Common Stock, $.001 par value.......  1,382,637 shares (2)     $ 4.18 (3)     $5,779,423 (4)      $1,993
Common Stock, $.001 par value.......   797,737 shares (5)      $ 9.25 (6)     $7,379,067 (7)      $2,545
1995 Director Option Plan
Common Stock, $.001 par value.......    60,000 shares (8)      $13.00 (9)     $ 780,000 (10)      $ 269
Common Stock, $.001 par value.......   90,000 shares (11)      $ 9.25 (6)      $ 832,500 (7)      $ 288
1995 Employee Stock Purchase Plan
Common Stock, $.001 par value.......   250,000 shares (12)     $ 7.87 (13)    $1,967,500 (14)     $ 679
(1)In  addition, pursuant to Rule 416(c) under  the Securities Act of 1933 (the
    "Act"), this Registration Statement also  covers an indeterminate amount  of
    interests  to  be offered  or sold  pursuant to  the employee  benefit plans
    described herein.
 
 (2)For the sole  purpose of  calculating the  registration fee,  the number  of
    shares  to be registered  under this Registration  Statement has been broken
    down into  five subtotals.  This subtotal  represents the  number of  shares
    issuable  upon exercise of currently  outstanding options (options that have
    been granted as of the date of this Registration Statement) issued under the
    1993 Employee and Consultant Stock Plan.
 
 (3)Calculated in  accordance with  Rule 457(h)  under the  Act solely  for  the
    purpose  of calculating the total registration fee. Calculation based on the
    weighted average exercise price (rounded to  the nearest cent) at which  the
    options outstanding whose exercise will result in the issuance of the shares
    being registered may be exercised.
 
 (4)Calculated  in  accordance  with Rule  457(h)  under  the Act  based  on the
    aggregate exercise price of all  currently outstanding options as  described
    in note 2 above.
 
 (5)This  subtotal represents  the number  of shares  issuable upon  exercise of
    options that are available  for grant, but have  not yet been granted  under
    the 1993 Employee and Consultant Stock Plan.
 
 (6)Estimated  in  accordance with  Rule  457(h) under  the  Act solely  for the
    purpose of calculating the total registration fee. The calculation is  based
    upon  the  closing price  of  the Common  Stock  as reported  on  the Nasdaq
    National Market on July 15, 1996 because  the price at which the options  to
    be granted in the future may be exercised is not currently determinable.
 
 (7)Calculated  in  accordance  with Rule  457(h)  under  the Act  based  on the
    aggregate exercise price for options available for grant.
 
 (8)This subtotal  represents the  number of  shares issuable  upon exercise  of
    currently outstanding options (options that have been granted as of the date
    of this Registration Statement) issued under the 1995 Director Option Plan.
 
 (9)Calculated  in  accordance with  Rule 457(h)  under the  Act solely  for the
    purpose of calculating the total registration fee. The calculation is  based
    upon  the  closing price  of  the Common  Stock  as reported  on  the Nasdaq
    National Market on January 31, 1996.
 
(10)Calculated in  accordance  with Rule  457(h)  under  the Act  based  on  the
    aggregate  exercise price of all  currently outstanding options as described
    in note 8 above.
 
(11)This subtotal  represents the  number of  shares issuable  upon exercise  of
    options  that are available for  grant, but have not  yet been granted under
    the 1995 Director Option Plan.
 
(12)This subtotal represents the number of shares authorized to be issued  under
    the 1995 Employee Stock Purchase Plan.
 
(13)Estimated  in  accordance with  Rule  457(h) under  the  Act solely  for the
    purpose of calculating  the total registration  fee. Calculation based  upon
    85%  (see explanation  in following  sentence) of  the closing  price of the
    Common Stock as  reported on  the Nasdaq National  Market on  July 15,  1996
    because  the price at which  the options to be granted  in the future may be
    exercised is not currently  determinable. The purchase price  of a share  of
    Common  Stock pursuant to the 1995  Employee Stock Purchase Plan, which plan
    is incorporated by  reference herein,  is equal to  85% of  the Fair  Market
    Value  of a share of Common Stock on either the first day or the last day of
    the relevant offering period, whichever is lower.
 
(14)Calculated in  accordance  with Rule  457(h)  under  the Act  based  on  the
    aggregate  exercise price for all options  available as described in note 12
    above.
PART II
               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT
 
ITEM 3.  INFORMATION INCORPORATED BY REFERENCE
 
    The following documents and information previously filed with the Securities
and Exchange Commission are hereby incorporated by reference.
 
    (a)The  audited financial statements for  the Registrant's fiscal year ended
       December 31,  1995 contained  in the  Prospectus filed  pursuant to  Rule
424(b)(4) under the Securities Act of 1933 on February 2, 196.
 
    (b)The  Registrant's Quarterly  Report on  Form 10-Q  for the  quarter ended
       March 31, 1996, filed pursuant to Section  13 of the Exchange Act on  May
14, 1996.
 
    (c)The  description of the Common Stock  of the Registrant that is contained
       in the Registration Statement on Form 8-A filed pursuant to Section 12 of
the Exchange Act on December 1, 1995.
 
    (d)All documents filed by the Registrant pursuant to Sections 13(a),  13(c),
       14  and  15(d) of  the  Exchange Act  subsequent  to the  filing  of this
Registration Statement and  prior to  the filing of  a post-effective  amendment
which  indicates that all securities offered have been sold or which deregisters
all securities then  remaining unsold,  shall be  deemed to  be incorporated  by
reference  in the Registration Statement and to be part thereof from the date of
filing of such documents.
 
ITEM 4.  DESCRIPTION OF SECURITIES.
 
    Not applicable.
 
ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.
 
    Certain  members  of  Wilson  Sonsini  Goodrich  and  Rosati,   Professional
Corporation,   beneficially  own   twenty  thousand   (20,000)  shares   of  the
Registrant's Common Stock.
 
ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.
 
    Section 145 of  the General  Corporation Law  of Delaware  provides for  the
indemnification  of  officers, directors  and  other corporate  agents  in terms
sufficiently broad to indemnify such  persons, under certain circumstances,  for
certain liabilities (including reimbursement of expenses incurred) arising under
the Securities Act of 1933 (the "Securities Act").
 
    The  Registrant's  Bylaws provide  that the  Registrant shall  indemnify its
directors and officers and  may indemnify its other  officers and employees  and
other  agents to the fullest extent permitted by law, including circumstances in
which indemnification is otherwise discretionary under Delaware law.
 
    The Registrant has  adopted provisions in  its Certificate of  Incorporation
that eliminate the personal liability of its directors and officers for monetary
damages arising from a breach of their fiduciary duties in certain circumstances
to  the  fullest  extent  permitted  by law  and  authorizes  the  Registrant to
indemnify its directors  and officers to  the fullest extent  permitted by  law.
Such  limitation  of liability  does not  affect  the availability  of equitable
remedies such as injunctive relief or recission.
 
    The Registrant entered  into indemnification agreements  with its  executive
officers  and directors containing provisions which are in some respects broader
that  the  specific   indemnification  provisions  contained   in  the   General
Corporation  Laws of  Delaware. The  indemnification agreements  may require the
Company, among other things,  to indemnify such  officers and directors  against
certain  liabilities that  may arise  by reason  of their  status or  service as
directors or officers (other than liabilities arising from willful misconduct of
a culpable nature). These agreements also indemnify the directors and  executive
officers  for certain expenses (including attorney's fees), judgments, fines and
settlement amounts incurred  as a result  of any proceeding  against them as  to
which they could be indemnified.
 
                                      II-1
ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.
 
    Not applicable.
 
ITEM 8.  EXHIBITS.
EXHIBIT
NUMBER                                                          DOCUMENT
- ------ ---------------------------------------------------------------------------------------------------------------------------
5.1 Opinion of Wilson Sonsini Goodrich & Rosati, Professional Corporation, as to the legality of securities being registered.
  *10.2 1993 Employee and Consultant Stock Plan and form of Stock Option Agreement thereunder.
  *10.3 1995 Director Option Plan and form of Stock Option Agreement thereunder.
  *10.4 1995 Employee Stock Purchase Plan and forms of agreements thereunder.
   23.1 Consent of Ernst & Young LLP, Independent Auditors
   23.2 Consent of Wilson Sonsini Goodrich & Rosati, Professional Corporation (contained in Exhibit 5.1 hereto)
   24.1 Power of Attorney
- ------------------------
*Incorporated  by reference  to exhibits  filed with  the Company's Registration
 Statement on Form S-1  (file no. 33-99908), in  the form declared effective  on
 January 31, 1996.
 
ITEM 9.  UNDERTAKINGS.
 
    (a)The undersigned Registrant hereby undertakes:
 
       (1) To  file, during any period in which  offers or sales are being made,
           post-effective amendment to  this Registration  Statement to  include
    any  material  information  with respect  to  the plan  of  distribution not
    previously disclosed in the Registration Statement or any material change to
    such information in the Registration Statement.
 
       (2) That,  for  the  purpose  of  determining  any  liability  under  the
           Securities Act, each such post-effective amendment shall be deemed to
    be  a new registration statement relating to the securities offered therein,
    and the offering of such securities at  that time shall be deemed to be  the
    initial bona fide offering thereof.
 
       (3) To  remove from registration  by means of  a post-effective amendment
           any of the  securities being  registered which remain  unsold at  the
    termination of the offering.
 
    (b)The  undersigned  Registrant  hereby  undertakes  that,  for  purposes of
       determining any liability under the  Securities Act of 1933, each  filing
of  the Registrant's annual report pursuant to Section 13(a) or Section 15(d) of
the Securities Exchange Act  of 1934 (and, where  applicable, each filing of  an
employee  benefit  plan's  annual  report  pursuant  to  Section  15(d)  of  the
Securities Exchange  Act of  1934)  that is  incorporated  by reference  in  the
Registration  Statement  shall  be deemed  to  be a  new  registration statement
relating to the securities therein, and the offering of such securities at  that
time shall be deemed to be an initial bona fide offering thereof.
 
    (c)Insofar  as indemnification for liabilities  arising under the Securities
       Act of  1933 may  be  permitted to  directors, officers  and  controlling
persons  of the Registrant  pursuant to the  foregoing provisions, or otherwise,
the Registrant  has been  advised that  in  the opinion  of the  Securities  and
Exchange  Commission such indemnification is  against public policy as expressed
in the Securities  Act and  is, therefore, unenforceable.  In the  event that  a
claim  for indemnification against  such liabilities (other  than the payment by
the  Registrant  of  expenses  incurred  or  paid  by  a  director,  officer  or
controlling  person of the  Registrant in the successful  defense of any action,
suit or proceeding) is
 
                                      II-2
asserted by such director, officer, or controlling person in connection with the
securities being registered, the Registrant will,  unless in the opinion of  its
counsel  the matter has been settled by controlling precedent, submit to a court
of appropriate jurisdiction the question  whether such indemnification by it  is
against  public policy as expressed in the Act and will be governed by the final
adjudication of such issued.
 
                                      II-3
SIGNATURES
 
    Pursuant  to the requirements of the  Securities Act of 1933, the Registrant
certifies that it has  reasonable grounds to  believe that it  meets all of  the
requirements  for  filing on  Form  S-8 and  has  duly caused  this Registration
Statement to  be  signed  on  its behalf  by  the  undersigned,  thereunto  duly
authorized, in the City of Seattle, State of Washington, on July 22, 1996.
 
                                          HEARTSTREAM, INC.
 
                                                      /s/ ALAN J. LEVY
                                                           By:
                                          --------------------------------------
                                                        Alan J. Levy
                                                President and Chief Executive
                                                         Officer
 
                               POWER OF ATTORNEY
 
    KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Alan J. Levy and Gary Onn, jointly and severally,
as  his or her attorney-in-fact, each with the power of substitution, for him or
her in  any and  all capacities,  to sign  any amendments  to this  Registration
Statement  on Form S-8,  and to file  the same, with  exhibits thereto and other
documents in connection therewith, with the Securities and Exchange  Commission,
hereby  ratifying and confirming all that  the said attorneys-in-fact, or his or
her substitute or substitutes, may do or cause to be done by virtue hereof.
 
    Pursuant  to  the  requirements  of   the  Securities  Act  of  1933,   this
Registration  Statement  has  been  signed  by  the  following  persons  in  the
capacities and on the date indicated.
SIGNATURE                                        TITLE                            DATE
- ---------------------------------------------  ---------------------------------------------  ----------------
/s/ ALAN J. LEVY                 President, Chief Executive Officer and         July 22, 1996
     -----------------------------------        Director* (Principal Executive Officer)
                Alan J. Levy
 
                /s/ GARY ONN                   Director of Finance and Administration         July 22, 1996
     -----------------------------------        (Principal Financial and Accounting Officer)
                  Gary Onn
 
          /s/ MICHAEL J. LEVINTHAL             Director*                                      July 18, 1996
     -----------------------------------
            Michael J. Levinthal
 
             /s/ ELLEN M. FEENEY               Director*                                      July 19, 1996
     -----------------------------------
               Ellen M. Feeney
 
            /s/ FRANK M. FISCHER               Director*                                      July 20, 1996
     -----------------------------------
              Frank M. Fischer
 
             /s/ WENDE S. HUTTON               Director*                                      July 18, 1996
     -----------------------------------
               Wende S. Hutton
 
             /s/ MARK B. KNUDSON               Director*                                      July 19, 1996
     -----------------------------------
               Mark B. Knudson
 
             /s/ KURT C. WHEELER               Director*                                      July 18, 1996
     -----------------------------------
               Kurt C. Wheeler
- ------------------------
* The employee  benefit plans  being registered  pursuant to  this  Registration
  Statement  are  subject to  administration by  the Board  of Directors  of the
  Registrant. Option grants under  the 1995 Director  Option Plan, however,  are
  automatic.
 
                                      II-4
INDEX TO EXHIBITS
EXHIBIT                                              DESCRIPTION                                               PAGE
- -----------  ------------------------------------------------------------------------------------------------  ---------
5.1  Opinion of Wilson Sonsini Goodrich & Rosati, Professional Corporation, as to the legality of
              securities being registered....................................................................
      *10.2  1993 Employee and Consultant Stock Plan and form of Stock Option Agreement thereunder.
      *10.3  1995 Director Option Plan and form of Stock Option Agreement thereunder.
      *10.4  1995 Employee Stock Purchase Plan and forms of agreements under.
       23.1  Consent of Ernst & Young, LLP Independent Auditors..............................................
       23.2  Consent of Wilson Sonsini Goodrich & Rosati, Professional Corporation (contained in Exhibit 5.1
              hereto)........................................................................................
       24.1  Power of Attorney (See Page II-4)...............................................................
- ------------------------
*Incorporated  by reference  to exhibits  filed with  the Company's Registration
 Statement on Form S-1  (file no. 33-99908), in  the form declared effective  on
 January 31, 1996.