UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 3)*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.  ¨

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

The information required on 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).

Persons who respond to the collection of information contained in this form are not

required to respond unless the form displays a currently valid OMB control number.

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13D

Schedule 13D

This Amendment No. 3 to the statement on Schedule 13D (this “Amendment No. 3”) amends and supplements the statement on Schedule 13D filed on August 8, 2008 (the “Original 13D”) as amended by Amendment No. 1 to the statement on Schedule 13D filed on February 4, 2010 (“Amendment No. 1”) and Amendment No. 2 to the statement on Schedule 13D filed on October 28, 2010 (“Amendment No. 2” and together with the Original 13D, Amendment No. 1 and this Amendment No. 3, the “Schedule 13D”), and relates to the common stock, $.001 par value (the “Common Stock”) of World Heart Corp. (the “Issuer”) having its principal executive office at 4750 Wiley Post Way, Suite 120, Salt Lake City, UT 84116.

The purpose of this Amendment is to reflect the disposition by the Reporting Persons of 2,341,920 shares of Common Stock and warrants to purchase up to an additional 2,341,920 shares of Common Stock in the aggregate. Except as specifically provided herein, this Amendment No. 3 does not modify any of the information previously reported on the Original 13D. Capitalized terms used but not otherwise defined in this Amendment No. 3 shall have the meanings ascribed to them in the Original 13D.

This statement is being filed by New Leaf Ventures II, L.P. (“NLV II”), New Leaf Venture Associates II, L.P. (“NLV Associates”) and New Leaf Venture Management II, L.L.C. (“NLV Management” and together with NLV II and NLV Associates, the “Reporting Entities”) and Philippe O. Chambon (“Chambon”), James Niedel (“Niedel”), Vijay Lathi (“Lathi”), Ronald Hunt (“Hunt”), Srinivas Akkaraju (“Akkaraju”) and Jeani Delagardelle (“Delagardelle” and together with Chambon, Niedel, Lathi, Hunt and Akkaraju, the “Managing Directors”). Delagardelle is also a director of the Issuer. The Reporting Entities and the Managing Directors collectively are referred to as the “Reporting Persons”.

The address of the principal business office of NLV II, NLV Associates, NLV Management, Chambon, Niedel and Hunt is New Leaf Venture Partners, Times Square Tower, 7 Times Square, Suite 3502, New York, NY 10036. The address of the principal business office of Lathi, Akkaraju and Delagardelle is New Leaf Venture Partners, 2500 Sand Hill Road, Suite 203, Menlo Park, CA 94025.

The principal business of NLV II is to make, hold and dispose of equity and equity-related investments, principally in healthcare, medical device and life sciences companies. The principal business of NLV Associates is to act as the sole general partner of NLV II. The principal business of NLV Management is to act as the sole general partner of NLV Associates. The principal business of each of the Managing Directors is to manage the Reporting Entities and a number of affiliated partnerships with similar businesses.

During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Each of NLV II and NLV Associates is a limited partnership organized under the laws of the State of Delaware. NLV Management is a limited liability company organized under the laws of the State of Delaware. Each Managing Director other than Philippe O. Chambon is a citizen of the United States. Philippe O. Chambon is a citizen of France.

Not applicable.

13D

NLV II disposed of the Common Stock pursuant to a merger agreement (the “Merger Agreement”) by and among the Issuer, Ocean Acquisition Holding Inc. (“Ocean”) and Heartware International, Inc. (“Heartware”) in exchange for 19,560 shares of Heartware common stock having a market value of $89.79 per share (based on a ten day Heartware average stock price, ending on and including August 1, 2012) and a cash payment of $72.21. NLV II was the record owner of a warrant (the “Warrant”), exercisable at an exercise price of $2.31 per share for up to 2,341,920 shares of Common Stock. The Warrant was cancelled in the merger in exchange for a cash payment of $233,021.04. Except as set forth above, none of the Reporting Persons has any present plans which relate to or would result in:

The percentage of outstanding Common Stock of the Issuer which may be deemed to be beneficially owned by each Reporting Person is set forth on Line 13 of such Reporting Person’s cover sheet.

Each of the Reporting Persons, except NLV II, disclaims beneficial ownership of the NLV II Shares except to the extent of their pecuniary interest therein, if any.

13D

Not applicable.

Exhibit 99.1 – Agreement regarding filing of joint Schedule 13D.

Exhibit 99.2 – Powers of Attorney regarding Schedule 13D filings.

13D

SIGNATURE

After reasonable inquiry and to the best of its knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Date: August 13, 2012, 2012

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EXHIBIT 99.1

AGREEMENT

Pursuant to Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, the undersigned hereby agree that only one statement containing the information required by Schedule 13D need be filed with respect to the ownership by each of the undersigned of shares of stock of World Heart Corp.

EXECUTED this 13th day of August, 2012.

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EXHIBIT 99.2

POWER OF ATTORNEY

KNOWN ALL MEN BY THESE PRESENTS, that the undersigned hereby constitutes and appoints CRAIG L. SLUTZKIN as his true and lawful attorney-in-fact and agent for him and in his name, place and stead, in any and all capacities, to sign any and all documents relating to any and all Securities and Exchange Commission filings which may be required, granting unto said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, thereby ratifying and confirming all that said attorney-in-fact may lawfully do or cause to be done by virtue hereof.

This power shall continue in effect until terminated in writing.

Dated: October 5, 2005

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POWER OF ATTORNEY

KNOWN ALL MEN BY THESE PRESENTS, that the undersigned hereby constitutes and appoints CRAIG L. SLUTZKIN as his/her true and lawful attorney-in-fact and agent for him/her and in his/her name, place and stead, in any and all capacities, to sign any and all documents relating to any and all Securities and Exchange Commission filings which may be required, granting unto said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he/she might or could do in person, thereby ratifying and confirming all that said attorney-in-fact may lawfully do or cause to be done by virtue hereof.

This power shall continue in effect until terminated in writing.

Dated: September 29, 2006

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POWER OF ATTORNEY

KNOWN ALL MEN BY THESE PRESENTS, that the undersigned hereby constitutes and appoints CRAIG L. SLUTZKIN as his true and lawful attorney-in-fact and agent for him and in his name, place and stead, in any and all capacities, to sign any and all documents relating to any and all Securities and Exchange Commission filings which may be required, granting unto said attorney-in-fact and agent full power and authority to do and perform each and every act and thing requisite and necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, thereby ratifying and confirming all that said attorney-in-fact may lawfully do or cause to be done by virtue hereof.

This power shall continue in effect until terminated in writing.

Dated: February 2, 2009