UNITED STATES SECURITIES AND EXCHANGE COMMISSION

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(Mark one)

Commission file number: 1-8145

Thoratec Corporation

Registrant’s telephone number, including area code: (925) 847-8600

Securities registered pursuant to Section 12(b) of the Exchange Act: None

Securities registered pursuant to Section 12(g) of the Exchange Act: Common Stock

     Indicate by a check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes þ No o

     Indicate by a check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. þ

     Indicate by a check mark whether the registrant is an accelerated filer (as defined in Exchange Act Rule 12(b)-2) Yes þ No o

     The aggregate market value of the voting stock held by non-affiliates computed by reference to the last sale reported of such stock on July 2, 2004, the last business day of the Registrant’s second fiscal quarter, as listed on The Nasdaq National Stock Market was $517,972,797.

     As of April 28, 2005, registrant had 48,266,917 shares of common stock outstanding.

EXPLANATORY NOTE:

     The registrant hereby amends its Annual Report on Form 10-K for the year ended January 1, 2005 to revise the Registrant’s disclosure under the heading “Controls and Procedures” in Item 9A and attaches Exhibits 31.1 and 31.2. Items in the Annual Report on Form 10-K not referenced below are not amended, and this amendment does not reflect events occurring after the original filing of the Annual Report on Form 10-K, or modify or update those disclosures as presented in the Form 10-K except to the extent set forth herein. Items referenced herein are amended as set forth below.

 

TABLE OF CONTENTS

PART II
	Item 9A. Controls and Procedures
PART IV
	ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K
SIGNATURES
INDEX TO EXHIBITS
EXHIBIT 31.1
EXHIBIT 31.2

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Table of Contents

PART II

Item 9A. Controls and Procedures

Attached as exhibits to this Form 10-K are certifications of our Chief Executive Officer and principal financial officer, which are required in accordance with Rule 13a-14 of the Securities Exchange Act of 1934, as amended. This “Controls and Procedures” section includes information concerning the controls and controls evaluation referred to in the certifications. Item 8 of this Form 10-K sets forth the report of Deloitte & Touche LLP, our independent registered public accounting firm, regarding its audit of our internal control over financial reporting and of management’s assessment of internal control over financial reporting. This section should be read in conjunction with the certifications and the Deloitte & Touche LLP report for a more complete understanding of the topics presented .

Disclosure Controls and Procedures

An evaluation was performed under the supervision and with the participation of our management, including our Chief Executive Officer and principal financial officer, of the effectiveness of the design and operation of our disclosure controls and procedures, as defined in Rule 13a-15(e) under the Exchange Act, as of January 1, 2005. The evaluation of our disclosure controls and procedures included a review of our processes and implementation and the effect on the information generated for use in this Annual Report on Form 10-K. In the course of this evaluation, we sought to identify any significant deficiencies or material weaknesses in our disclosure controls and procedures, to determine whether we had identified any acts of fraud involving personnel who have a significant role in our disclosure controls and procedures, and to confirm that any necessary corrective action, including process improvements, was taken. This type of evaluation is done quarterly so that our conclusions concerning the effectiveness of these controls can be reported in our periodic reports filed with the SEC. The overall goals of these evaluation activities are to monitor our disclosure controls and procedures and to make modifications as necessary. We intend to maintain these disclosure controls and procedures, modifying them as circumstances warrant.

Based on that evaluation, our management, including the Chief Executive Officer and principal financial officer, concluded that as of January 1, 2005 the Company’s disclosure controls and procedures, as defined in Rule 13a-15(e) under the Exchange Act, were effective.

Changes to Internal Controls

Prior to year end 2004, as part of the implementation of the Section 404 of the Sarbanes Oxley Act, the Company instituted internal controls which were designed to and did detect the situation which resulted in the restatement of the pro forma stock compensation fair value disclosures for the years ended January 3, 2004 and December 28, 2002. Management concluded that the control deficiency which resulted in the restatement was not indicative of a material weakness in internal controls as of January 1, 2005. There have been no other changes in our internal controls over financial reporting during the fiscal year ended January 1, 2005 that have materially affected or are reasonably likely to materially affect our internal control over financial reporting.

Inherent Limitations on Controls and Procedures

Our management, including the Chief Executive Officer and the principal financial officer, does not expect that internal controls will prevent all error and all fraud. A control system, no matter how well designed and operated, can only provide reasonable assurances that the objectives of the control system are met. The design of a control system reflects resource constraints; the benefits of controls must be considered relative to their costs. Because there are inherent limitations in all control systems, no evaluation of controls can provide absolute assurance that all control issues and instances of fraud, if any, within the company have been or will be detected. As these inherent limitations are known features of the financial reporting process it is possible to design into the process safeguards to reduce, though not eliminate, these risks. These inherent limitations include the realities that judgments in decision-making can be faulty and that breakdowns occur because of simple error or mistake. Controls can be circumvented by the individual acts of some persons, by collusion of two or more people, or by management override of the control. The design of any system of controls is based in part upon certain assumptions about the

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likelihood of future events. While our disclosure controls and procedures are designed to provide reasonable assurance of achieving their objectives, there can be no assurance that any design will succeed in achieving its stated goals under all future conditions; over time, controls may become inadequate because of changes in conditions or deterioration in the degree of compliance with the policies or procedures. Because of the inherent limitations in a cost-effective control system, misstatements due to error or fraud may occur and not be detected.

We intend to review and evaluate the design and effectiveness of our disclosure controls and procedures on an ongoing basis and to improve our controls and procedures over time and to correct any deficiencies that we may discover in the future. While our Chief Executive Officer and principal financial officer have concluded that, as of January 1, 2005, the design of our disclosure controls and procedures, as defined in Rule 13a-15(e) under the Exchange Act, was effective, future events affecting our business may cause us to significantly modify our disclosure controls and procedures.

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PART IV

ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K.

(a)(3) Exhibits

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Filed herewith

(1)	Filed as an Exhibit to Thoratec’s Annual Report on Form 10-K for the fiscal year ended December 28, 2002 filed with the SEC on March 20, 2003 and incorporated herein by reference.
(2)	Filed as an Exhibit to Thoratec’s Form 8-K filed with the SEC on March 3, 2005.
(3)	Filed as an Exhibit to Thoratec’s Form 8-A12G filed with the SEC on May 3, 2002 (Registration No. 000-49798), and incorporated herein by reference.
(4)	Filed as an Exhibit to Thoratec’s Quarterly Report on Form 10-Q for the fiscal quarter ended July 3, 2004 filed with the SEC on August 12, 2004, and incorporated herein by reference.
(5)	Included as an exhibit to Exhibit 4.2.
(6)	Filed as an Exhibit to Thoratec’s Annual Report on Form 10-K for the fiscal year ended December 29, 1990 filed with the SEC on March 28, 1991, and incorporated herein by reference.
(7)	Filed as an Exhibit to Thoratec Cardiosystems’ Registration Statement on Form S-1 (Registration No. 33-25144) and incorporated herein by reference.
(8)	Filed as an Exhibit to Thoratec’s Annual Report on Form 10-K for the fiscal year ended January 1, 1994 filed with the SEC on March 22, 1994, and incorporated herein by reference.
(9)	Filed as an Exhibit to Thoratec Cardiosystems’ Quarterly Report on Form 10-Q for the fiscal quarter ended July 3, 1993 and incorporated herein by reference.

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(10)	Filed as an Exhibit to Thoratec’s Registration Statement on Form S-8 filed with the SEC on September 12, 1996, (Registration No. 333-11883) and incorporated herein by reference.

(11)	Filed as an Exhibit to Thoratec’s Annual Report on Form 10-K for the fiscal year ended January 3, 2004 filed with the SEC on March 17, 2004 and incorporated herein by reference.

(12)	Filed as an Exhibit to Thoratec’s Quarterly Report on Form 10-Q for the fiscal quarter ended June 29, 1996, filed with the SEC on August 13, 1996, and incorporated herein by reference.

(13)	Filed as an Exhibit to Thoratec’s Quarterly Report on Form 10-Q for the fiscal quarter ended June 28, 1997, filed with the SEC on July 30, 1997, and incorporated herein by reference.

(14)	Filed as an Exhibit to Thoratec’s Quarterly Report on Form 10-Q for the fiscal quarter ended September 27, 1997 filed with the SEC on November 12, 1997, and incorporated herein by reference.

(15)	Filed as an Exhibit to Thoratec’s Registration Statement on Form S-8 filed with the SEC on June 18, 2003 (Registration No. 333-106238), and incorporated herein by reference.

(16)	Filed as an Exhibit to Thoratec Cardiosystems’ Quarterly Report on Form 10-Q for the fiscal quarter ended July 3, 1999 filed with the SEC on August 5, 1999, and incorporated herein by reference.

(17)	Filed as an Annex to Thoratec’s Registration Statement on Form S-4/A, filed with the SEC on December 29, 2000 (Registration No. 333-72128), and incorporated herein by reference.

(18)	Filed as an Exhibit to Thoratec’s Form 10-K405 filed with the SEC on March 15, 2002 (Registration No. 033-72502), and incorporated herein by reference.

(19)	Filed as an Exhibit to Thoratec’s Form S-8 POS filed with the SEC on July 1, 2002 (Registration No. 333-90768), and incorporated herein by reference.

(20)	Filed as an Exhibit to Thoratec’s Quarterly Report on Form 10-Q for the fiscal quarter ended March 29, 2003 filed with the SEC on May 13, 2003, and incorporated herein by reference.
(21)	Filed as an Exhibit to Thoratec’s Form 8-K filed with the SEC on December 20, 2004.
(22)	Filed as an Exhibit to Thoratec’s Form 10-K filed with the SEC on March 16, 2005.

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SIGNATURES

     In accordance with Section 13 or Section 15(d) of the Exchange Act, the Registrant has duly caused this Form 10-K/A to be signed on its behalf by the undersigned, thereunto duly authorized on this 5th day of May 2005.

	THORATEC CORPORATION
	By:	/s/ D. Keith Grossman
		D. Keith Grossman
		Chief Executive Officer

Date: May 5, 2005

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In accordance with the Exchange Act, this report has been signed below by the following persons on behalf of the Thoratec Corporation and in the capacities and on the dates indicated.

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INDEX TO EXHIBITS

31.1	Section 302 Certification of Chief Executive Officer.
31.2	Section 302 Certification of principal financial officer.

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