SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549
SCHEDULE 13G
(Rule 13d-102)
INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
TO RULES 13d-1(b),(c), AND (d) AND AMENDMENTS THERETO FILED
PURSUANT TO RULE 13d-2
(AMENDMENT NO. 3)
Thoratec Corporation
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(Name of Issuer)
Common Stock, No Par Value Per Share
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(Title of Class of Securities)
885175307
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(CUSIP Number)
12/31/2006
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(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:
/X/ Rule 13d-1(b)
/ / Rule 13d-1(c)
/ / Rule 13d-1(d)
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*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities,
and for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.
The information required in the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 ("Act") or otherwise subject to the liabilities of that section of
the Act but shall be subject to all other provisions of the Act (however, see
the Notes).
Page 1 of 4 Pages
CUSIP NO. 885175307 13G PAGE 2 OF 4 PAGES
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1 NAME OF REPORTING PERSONS
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
Massachusetts Financial Services Company ("MFS")
I.R.S. Identification No.: 04-2747644
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2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*
(a) / / (b) / / Not Applicable
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3 SEC USE ONLY
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4 CITIZENSHIP OR PLACE OF ORGANIZATION
Delaware
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NUMBER OF 5 SOLE VOTING POWER
SHARES 2,995,270 shares of common stock
BENEFICIALLY
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OWNED BY 6 SHARED VOTING POWER
EACH None
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REPORTING 7 SOLE DISPOSITIVE POWER
PERSON 2,995,270 shares of common stock
WITH
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8 SHARED DISPOSITIVE POWER
None
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9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
2,995,270 shares of common stock, of which shares are also beneficially
owned by certain other non-reporting entities as well as MFS.
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10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* / /
Not applicable
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11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9
5.8
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12 TYPE OF REPORTING PERSON
IA
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SCHEDULE 13G PAGE 3 OF 4 PAGES
ITEM 1: (a) NAME OF ISSUER:
SEE COVER PAGE
(b) ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES:
6035 Stoneridge Drive
Pleasanton, CA 94588
ITEM 2: (a) NAME OF PERSON FILING:
See item 1 on page 2
(b) ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE:
500 Boylston Street
Boston, MA 02116
(c) CITIZENSHIP:
See Item 4 on page 2
(d) TITLE OF CLASS OF SECURITIES:
See Cover Page
(e) CUSIP NUMBER:
See Cover Page
ITEM 3: The person filing is an investment adviser in accordance with
Rule 13d-1(b)(1)(ii)(E)
ITEM 4: OWNERSHIP
(a) AMOUNT BENEFICIALLY OWNED:
See Item 9 on page 2
(b) PERCENT OF CLASS:
See Item 11 on page 2
(c) NUMBER OF SHARES AS TO WHICH SUCH PERSON HAS VOTING AND
DISPOSITIVE POWERS (SOLE AND SHARED):
See Items 5-8 on page 2
SCHEDULE 13G PAGE 4 OF 4 PAGES
ITEM 5: OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS: / /
Not applicable
ITEM 6: OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON:
Not applicable
ITEM 7: IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH
ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING
COMPANY:
Not applicable
ITEM 8: IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP:
Not applicable
ITEM 9: NOTICE OF DISSOLUTION OF GROUP:
Not applicable
ITEM 10: CERTIFICATIONS:
By signing below I certify that, to the best of my knowledge and
belief, the securities referred to above were acquired and are held in the
ordinary course of business and were not acquired and are not held for the
purpose of or with the effect of changing or influencing the control of
the issuer of the securities and were not acquired and are not held in
connection with or as a participant in any transaction having that purpose or
effect.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this statement is true,
complete and correct.
Date: February 12, 2007
Massachusetts Financial Services Company
By: /s/ JEREMY KREAM
Jeremy Kream
Vice President and Assistant Secretary