CONVERTIBLE NOTE PURCHASE AGREEMENT

Exhibit 10.5

CONVERTIBLE NOTE PURCHASE AGREEMENT

This Convertible Note Purchase Agreement (this “Agreement”) is dated as of November 14, 2011, by and among Cambridge Heart, Inc., a Delaware corporation (the “Company”), and each of the purchasers listed on Exhibit A hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”).

WHEREAS, subject to the terms and conditions set forth in this Agreement and pursuant to Section 4(2) of the Securities Act (as defined below) and Rule 506 promulgated thereunder, the Company desires to issue and sell, and each Purchaser, severally and not jointly, desires to purchase, a convertible subordinated promissory note in substantially the form attached to this Agreement as Exhibit B (together, the “Notes”), which shall be convertible on the terms stated therein into securities of the Company. The Note and the equity securities issuable upon conversion thereof (and any securities issuable upon conversion of such equity securities) are collectively referred to herein as the “Securities.”

AGREEMENT

NOW, THEREFORE, IN CONSIDERATION of the mutual covenants contained in this Agreement, and for other good and valuable consideration the receipt and adequacy of which are hereby acknowledged, the Company and each Purchaser agrees as follows:

1. Purchase and Sale of Notes.

(a) Sale and Issuance of Notes. Subject to the terms and conditions of this Agreement, each Purchaser hereby unconditionally agrees on the Closing Date (as defined below) (a) to acquire from the Company the Note having the terms, rights and preferences set forth therein, and (b) to make a cash loan to the Company in the principal amount thereof and set forth on Exhibit A hereto (the “Subscription Amount”). The Purchaser’s total loan in respect of the Note shall be paid by the Purchaser on the Closing Date by wire transfer of immediately available funds to an account designated by the Company. The Note shall be convertible into equity or debt securities of the Company as provided for under the Note. The Company’s agreements with each of the Purchasers are separate agreements, and the sale of the Notes to each of the Purchasers are separate sales, but all of the Notes together shall have the same terms and conditions and shall be regarded as a single loan to the Company.

(b) Closing. On November 14, 2011 (the “Closing Date”), subject to the terms and conditions set forth in this Agreement, each Purchaser shall deliver the Subscription Amount to the Company via wire transfer and the Company shall deliver to each Purchaser duly executed copies of the Note. The closing shall occur at the offices of Nutter McClennen and Fish, LLP, or such other location as the parties shall mutually agree.

(c) Acceptance of Subscription. The Company shall have no obligation hereunder until the Company shall execute and deliver to each of the Purchasers an executed

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copy of this Agreement. If this subscription is rejected prior to execution and delivery of this Agreement by the Company, this Agreement and all other documents executed by each of the Purchasers shall thereafter be of no further force or effect.

2. Representations and Warranties of the Company. The Company represents and warrants as of the date hereof and as of the Closing Date to the Purchasers as follows:

(a) Organization and Qualification. The Company is duly incorporated, validly existing and in good standing under the laws of the State of Delaware, with the requisite power and authority to own and use its properties and assets and to carry on its business as currently conducted. The Company is not in violation or default of any of the provisions of its certificate of incorporation and bylaws. The Company is duly qualified to conduct business and is in good standing as a foreign corporation in each jurisdiction in which the nature of the business conducted or property owned by it makes such qualification necessary, except where the failure to be so qualified or in good standing, as the case may be, would not have or reasonably be expected to result in a material adverse effect on the business, properties or financial condition of the Company, and no proceeding has been instituted in any such jurisdiction revoking, limiting or curtailing or seeking to revoke, limit or curtail such power and authority or qualification.

(b) Authorization; Enforcement. The Company has the requisite corporate power and authority to enter into and to consummate the transactions contemplated by this Agreement and the Note (the “Transaction Documents”) and otherwise to carry out its obligations hereunder and thereunder. The execution and delivery of each of the Transaction Documents by the Company and the consummation by it of the transactions contemplated thereby have been duly authorized by all necessary action on the part of the Company and no further action is required by the Company, its board of directors or its stockholders in connection therewith. Each Transaction Document has been (or upon delivery will have been) duly executed by the Company and, when delivered in accordance with the terms hereof and thereof, will constitute the valid and binding obligation of the Company enforceable against the Company in accordance with its terms except (i) as such enforceability may be limited by applicable bankruptcy, insolvency, reorganization, moratorium, liquidation and other similar laws of general application affecting enforcement of creditors’ rights generally, (ii) as limited by laws relating to the availability of specific performance, injunctive relief or other equitable remedies, and (iii) insofar as indemnification and contribution provisions may be limited by applicable law.

(c) No Conflicts. The execution, delivery and performance of the Transaction Documents by the Company and the consummation by the Company of the transactions contemplated hereby and thereby do not and will not conflict with or violate any provision of the Company’s certificate of incorporation or bylaws.

(d) Filings, Consents and Approvals. All consents, approvals, orders or authorizations of, or registrations, qualifications, designations, declarations or filings with, any governmental authority, required on the part of the Company in connection with the valid execution and delivery of this Agreement, the offer, sale or issuance of the Note, conversion of

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the Note, or the consummation of any other transaction contemplated hereby shall have been obtained and will be effective at the Closing, except for notices required or permitted to be filed with certain state and federal securities commissions, which notices will be filed on a timely basis.

(e) Issuance of the Securities. The Notes are duly authorized and, when issued and paid for in accordance with the applicable Transaction Documents, will be duly and validly issued, fully paid and nonassessable, free and clear of all liens imposed by the Company other than restrictions on transfer provided for in the Transaction Documents. Immediately prior to the conversion of the Note, the Company the shares of the Company’s stock issuable on conversion of the Notes will have been duly authorized and reserved for issuance, and when so issued in accordance with the terms of the applicable Transaction Documents and upon receipt of any necessary shareholder consent, will be validly issued, fully paid and nonassessable, free and clear of all liens imposed by the Company other than restrictions on transfer provided for in the Transaction Documents.

(f) SEC Reports; Financial Statements. The Company has filed all reports, schedules, forms, statements and other documents required to be filed by it under the Securities Act of 1933, as amended (the “Securities Act”) and the Securities Exchange Act of 1934, as amended (the “Exchange Act”), including pursuant to Section 13(a) or 15(d) thereof, for the two years preceding the date hereof (the foregoing materials, including the exhibits thereto and documents incorporated by reference therein, being collectively referred to herein as the “SEC Reports”) on a timely basis or has received a valid extension of such time of filing and has filed any such SEC Reports prior to the expiration of any such extension. As of their respective dates, the SEC Reports complied in all material respects with the requirements of the Securities Act and the Exchange Act and the rules and regulations of the Securities and Exchange Commission promulgated thereunder, and none of the SEC Reports, when filed, contained any untrue statement of a material fact or omitted to state a material fact required to be stated therein or necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading. The financial statements of the Company included in the SEC Reports comply in all material respects with applicable accounting requirements and the rules and regulations of the Securities and Exchange Commission with respect thereto as in effect at the time of filing. Such financial statements have been prepared in accordance with United States generally accepted accounting principles (“GAAP”) applied on a consistent basis during the periods involved, except as may be otherwise specified in such financial statements or the notes thereto and except that unaudited financial statements may not contain all footnotes required by GAAP, and fairly present in all material respects the financial position of the Company as of and for the dates thereof and the results of operations and cash flows for the periods then ended, subject, in the case of unaudited statements, to normal, immaterial, year-end audit adjustments.

(g) Private Placement. Assuming the accuracy of the Purchasers’ representations and warranties set forth in Section 3, no registration under the Securities Act is required for the offer and sale of the Securities by the Company to the Purchasers as contemplated hereby.

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3. Representations and Warranties of the Purchasers. Each Purchaser, for itself and for no other Purchaser, represents and warrants as of the date hereof and as of the Closing Date to the Company as follows:

(a) Authorization. Such Purchaser has full power and authority to enter into and to consummate the transactions contemplated by the Transaction Documents and otherwise to carry out the obligations thereunder, and each Transaction Document, when executed and delivered by the Purchaser, will constitute the valid and binding obligations of the Purchaser, enforceable against it in accordance with its terms, except (i) as limited by general equitable principles and applicable bankruptcy, insolvency, reorganization, moratorium and other laws of general application affecting enforcement of creditors’ rights generally, (ii) as limited by laws relating to the availability of specific performance, injunctive relief or other equitable remedies and (iii) insofar as indemnification and contribution provisions may be limited by applicable law. Each Purchaser not a natural person is duly organized, validly existing and in good standing under the laws of the jurisdiction of its organization with full right, corporate or partnership power and authority to enter into and to consummate the transactions contemplated by the Transaction Documents and otherwise to carry out its obligations thereunder. The execution, delivery and performance by each Purchaser that is not a natural person of the transactions contemplated by this Agreement have been duly authorized by all necessary corporate or similar action on the part of such Purchaser.

(b) Own Account. Such Purchaser understands that the Securities are restricted securities and have not been registered under the Securities Act or any applicable state securities law and is acquiring the Securities as principal for its own account and not with a view to or for distributing or reselling such Securities or any part thereof in violation of the Securities Act or any applicable state securities law, has no present intention of distributing any of such Securities in violation of the Securities Act or any applicable state securities law and has no arrangement or understanding with any other persons regarding the distribution of such Securities (this representation and warranty not limiting such Purchaser’s right to sell the Securities in compliance with applicable federal and state securities laws) in violation of the Securities Act or any applicable state securities law. The Purchaser does not have any agreement or understanding, directly or indirectly, with any person to distribute any of the Securities.

(c) Purchaser Status. At the time such Purchaser was offered the Securities, it was, and at the date hereof it is, and on each date on which it converts the Note, it will be an “accredited investor” as defined in Rule 501(a) under the Securities Act. Such Purchaser is not required to be registered as a broker-dealer under Section 15 of the Exchange Act.

(d) Experience of Such Purchaser. Such Purchaser, either alone or together with its representatives, has such knowledge, sophistication and experience in business and financial matters so as to be capable of evaluating the merits and risks of the prospective investment in the Securities, and has so evaluated the merits and risks of such investment. Such Purchaser is able to bear the economic risk of an investment in the Securities and, at the present time, is able to afford a complete loss of such investment.

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(e) Restricted Securities. The Purchaser understands that the Securities have not been, and will not be, registered under the Securities Act, by reason of a specific exemption from the registration provisions of the Securities Act which depends upon, among other things, the bona fide nature of the investment intent and the accuracy of the Purchaser’s representations as expressed herein. The Purchaser understands that the Securities are “restricted securities” under applicable U.S. federal and state securities laws and that, pursuant to these laws, the Purchaser must hold the Securities indefinitely unless they are registered with the Securities and Exchange Commission and qualified by state authorities, or an exemption from such registration and qualification requirements is available. The Purchaser further acknowledges that if an exemption from registration or qualification is available, it may be conditioned on various requirements including, but not limited to, the time and manner of sale, the holding period for the Securities, and on requirements relating to the Company which are outside of the Purchaser’s control, and which the Company is under no obligation and may not be able to satisfy.

(f) Legends. The Purchaser understands that the Securities, and any securities issued in respect thereof or exchange therefor, may bear one or all of the following legends:

(g) General Solicitation. Such Purchaser is not purchasing the Securities as a result of any advertisement, article, notice or other communication regarding the Securities published in any newspaper, magazine or similar media or broadcast over television or radio or presented at any seminar or any other general solicitation or general advertisement.

(h) Knowledge; Access to Information. Such Purchaser is aware of the Company’s business affairs and financial condition and has acquired sufficient information about the Company to reach an informed and knowledgeable decision to acquire the Securities. Such Purchaser acknowledges that it has been afforded (i) the opportunity to ask such questions

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as it has deemed necessary of, and to receive answers from, representatives of the Company concerning the terms and conditions of the offering of the Securities and the merits and risks of investing in the Securities; (ii) access to information about the Company and its financial condition, results of operations, business, properties, management and prospects sufficient to enable it to evaluate its investment; and (iii) the opportunity to obtain such additional information that the Company possesses or can acquire without unreasonable effort or expense that is necessary to make an informed investment decision with respect to the investment.

(i) Disclosure. Such Purchaser acknowledges and agrees that the Company does not make and has not made any representations or warranties with respect to the transactions contemplated hereby other than those specifically set forth in Section 2 hereof.

(j) Address. Such Purchaser’s address on the signature page hereto indicates the true state of residence of such Purchaser.

(k) Transactions in Securities. During the period from the commencement of negotiations between such Purchaser and the Company with respect to the transactions contemplated by this Agreement and the date hereof, such Purchaser has not established a short position with respect to the Company’s Common Stock.

(l) Confidentiality. Other than to other persons party to this Agreement, such Purchaser has maintained the confidentiality of all disclosures made to it in connection with this transaction (including the existence and terms of this transaction), and further agrees, and will cause its affiliates, to keep confidential and not to publish (by press release, press interview, or otherwise) or otherwise divulge or use for its own benefit or for the benefit of any third party any information of a confidential or proprietary nature furnished to it by the Company, or the existence and terms of this Agreement, without the prior written approval of the Company, except to such Purchaser’s employees and representatives as may need to know such information for purposes of the transactions contemplated by this Agreement, and except as required by applicable law. In the event of any such required disclosure, the Purchaser will (i) provide the Company with written notice of the required disclosure at least 48 hours in advance of such disclosure, and (ii) limit such disclosure to the minimum required under the applicable law or obligations, whether through a request for confidential treatment or otherwise. The confidentiality obligation described above shall not apply to information of the Company which: (a) was already known by such Purchaser prior to the time of its disclosure by the Company to such Purchaser; (b) is publicly available or later becomes publicly available through no fault of such Purchaser; or (c) is disclosed to such Purchaser by a third party having no similar confidentiality obligation. This obligation shall terminate three years after execution of this Agreement.

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4. Conditions of the Purchaser’s Obligations at Closing. The obligations of each Purchaser to the Company under this Agreement are subject to the fulfillment, on or before the Closing Date, of each of the following conditions, unless otherwise waived:

(a) Representations and Warranties. The representations and warranties of the Company contained in Section 2 shall be true on and as of the Closing Date with the same effect as though such representations and warranties had been made on and as of the Closing Date.

(b) Qualifications. All authorizations, approvals or permits, if any, of any governmental authority or regulatory body of the United States or of any state that are required in connection with the lawful issuance and sale of the Securities pursuant to this Agreement shall be obtained and effective as of the Closing Date.

5. Conditions of the Company’s Obligations at Closing. The obligations of the Company to each Purchaser under this Agreement are subject to the fulfillment, on or before the Closing Date, of each of the following conditions, unless otherwise waived:

(a) Representations and Warranties. The representations and warranties of the Purchasers contained in Section 3 shall be true on and as of the Closing Date with the same effect as though such representations and warranties had been made on and as of the Closing Date.

(b) Qualifications. All authorizations, approvals or permits, if any, of any governmental authority or regulatory body of the United States or of any state that are required in connection with the lawful issuance and sale of the Securities pursuant to this Agreement shall be obtained and effective as of the Closing Date.

(c) Payment of Principal Amount. Purchaser shall have paid by check or wire transfer of immediately available funds the principal amount set forth on the signature page of this Agreement.

6. Miscellaneous.

(a) Termination. This Agreement may be terminated by the holders of at least a majority of the outstanding principal amount of the Notes, by written notice to the other parties, if the Closing has not been consummated on or before November 15, 2011.

(b) Fees and Expenses. Except as expressly set forth in the Transaction Documents to the contrary, each party shall pay the fees and expenses of its advisers, counsel, accountants and other experts, if any, and all other expenses incurred by such party incident to the negotiation, preparation, execution, delivery and performance of this Agreement. The Company shall pay all transfer agent fees, stamp taxes and other taxes and duties levied in connection with the delivery of any Securities.

(c) Entire Agreement. The Transaction Documents, together with the exhibits and schedules thereto, contain the entire understanding of the parties with respect to the subject matter hereof and supersede all prior agreements and understandings, oral or written, with respect to such matters, which the parties acknowledge have been merged into such documents, exhibits and schedules.

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(d) Notices. Any and all notices or other communications or deliveries required or permitted to be provided hereunder shall be in writing and shall be deemed given and effective on the earliest of (a) personal delivery to the party to be notified, (b) when sent by confirmed telex or facsimile (provided that notice is also given under clause (c) below) if sent during normal business hours of the recipient; if not sent during normal business hours of the recipient, then on the next business day, or (c) receipt by the party to be notified by nationally recognized overnight courier service. The address for such notices and communications shall be as set forth on the signature pages attached hereto until changed by notice given in accordance with this Section.

(e) Amendments; Waivers. No provision of this Agreement may be waived or amended except in a written instrument signed, in the case of an amendment, by the Company and the holders of at least a majority of the outstanding principal amount of the Notes or, in the case of a waiver, by the party against whom enforcement of any such waiver is sought. No waiver of any default with respect to any provision, condition or requirement of this Agreement shall be deemed to be a continuing waiver in the future or a waiver of any subsequent default or a waiver of any other provision, condition or requirement hereof, nor shall any delay or omission of either party to exercise any right hereunder in any manner impair the exercise of any such right.

(f) Headings. The headings herein are for convenience only, do not constitute a part of this Agreement and shall not be deemed to limit or affect any of the provisions hereof. The language used in this Agreement will be deemed to be the language chosen by the parties to express their mutual intent, and no rules of strict construction will be applied against any party.

(g) Successors and Assigns. This Agreement shall be binding upon and inure to the benefit of the parties and their successors and permitted assigns. The Company may not assign this Agreement or any rights or obligations hereunder without the prior written consent of each Purchaser. Any Purchaser may assign any or all of its rights under this Agreement to any Person to whom such Purchaser assigns or transfers any Securities, provided such transferee agrees in writing to be bound, with respect to the transferred Securities, by the provisions hereof that apply to the “Purchasers”.

(h) No Third-Party Beneficiaries. This Agreement is intended for the benefit of the parties hereto and their respective successors and permitted assigns and is not for the benefit of, nor may any provision hereof be enforced by, any other Person.

(i) Governing Law. All questions concerning the construction, validity, enforcement and interpretation of the Transaction Documents shall be governed by and construed and enforced in accordance with the internal laws of the State of New York, without regard to the principles of conflicts of law thereof, except to the extent that the application of the General Corporation Law of the State of Delaware is mandatorily applicable. Each party agrees that all legal proceedings concerning the interpretations, enforcement and defense of the transactions contemplated by this Agreement and any other Transaction Documents (whether brought against a party hereto or its respective affiliates, directors, officers, stockholders, employees or agents) shall be commenced exclusively in the state and federal courts having jurisdiction for Middlesex County, Massachusetts, USA. Each party hereby irrevocably submits

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to the exclusive jurisdiction of the state and federal courts located in Middlesex County, Massachusetts, USA, for the adjudication of any dispute hereunder or in connection herewith or with any transaction contemplated hereby or discussed herein (including with respect to the enforcement of any of the Transaction Documents), and hereby irrevocably waives, and agrees not to assert in any suit, action or proceeding, any claim that it is not personally subject to the jurisdiction of any such court, or that such suit, action or proceeding has been commenced in an improper or inconvenient venue for such proceeding. Each party hereby irrevocably waives personal service of process and consents to process being served in any such suit, action or proceeding by mailing a copy thereof via registered or certified mail or overnight delivery (with evidence of delivery) to such party at the address in effect for notices to it under this Agreement and agrees that such service shall constitute good and sufficient service of process and notice thereof. Nothing contained herein shall be deemed to limit in any way any right to serve process in any manner permitted by law. Each party hereto hereby irrevocably waives, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to this Agreement or the transactions contemplated hereby. If any party shall commence an action or proceeding to enforce any provisions of the Transaction Documents, then the prevailing party in such action or proceeding shall be reimbursed by the other party for its reasonable attorneys’ fees and other costs and expenses incurred with the investigation, preparation and prosecution of such action or proceeding.

(j) Survival. The representations, warranties, agreements and covenants contained herein shall survive the closing and the delivery, conversion and/or exercise of the Securities, as applicable, for the applicable statute of limitations.

(k) Execution. This Agreement may be executed in two or more counterparts, all of which when taken together shall be considered one and the same agreement and shall become effective when counterparts have been signed by each party and delivered to the other party, it being understood that both parties need not sign the same counterpart. In the event that any signature is delivered by facsimile transmission, such signature shall create a valid and binding obligation of the party executing (or on whose behalf such signature is executed) with the same force and effect as if such facsimile signature page were an original thereof.

(l) Severability. If any provision of this Agreement is held to be invalid or unenforceable in any respect, the validity and enforceability of the remaining terms and provisions of this Agreement shall not in any way be affected or impaired thereby and the parties will attempt to agree upon a valid and enforceable provision that is a reasonable substitute therefor, and upon so agreeing, shall incorporate such substitute provision in this Agreement.

(m) Replacement of Securities. If any certificate or instrument evidencing any of the Securities is mutilated, lost, stolen or destroyed, the Company shall issue or cause to be issued in exchange and substitution for and upon cancellation thereof, or in lieu of and substitution therefore, a new certificate or instrument, but only upon receipt of evidence reasonably satisfactory to the Company of such loss, theft or destruction and customary and reasonable indemnity, if requested. The applicants for a new certificate or instrument under such circumstances shall also pay any reasonable third-party costs associated with the issuance of such replacement Securities. If a replacement certificate or instrument evidencing Securities is requested due to a mutilation thereof, the Company may require delivery of such mutilated certificate or instrument as a condition precedent to any issuance of a replacement Security.

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(n) Remedies. In addition to being entitled to exercise all rights provided herein or granted by law, including recovery of damages, each of the Purchasers and the Company will be entitled to specific performance under the Transaction Documents. The parties agree that monetary damages may not be adequate compensation for any loss incurred by reason of any breach of obligations described in the foregoing sentence and hereby agree to waive in any action for specific performance of any such obligation the defense that a remedy at law would be adequate.

(o) Independent Nature of Purchasers’ Obligations and Rights. The obligations of each Purchaser under any Transaction Document are several and not joint with the obligations of any other Purchaser, and no Purchaser shall be responsible in any way for the performance of the obligations of any other Purchaser under any Transaction Document. Nothing contained herein or in any Transaction Document, and no action taken by any Purchaser pursuant thereto, shall be deemed to constitute the Purchasers as a partnership, an association, a joint venture or any other kind of entity, or create a presumption that the Purchasers are in any way acting in concert or as a group with respect to such obligations or the transactions contemplated by the Transaction Document. Each Purchaser shall be entitled to independently protect and enforce its rights, including, without limitation, the rights arising out of this Agreement or out of the other Transaction Documents, and it shall not be necessary for any other Purchaser to be joined as an additional party in any proceeding for such purpose. Each Purchaser has been represented by its own separate legal counsel in their review and negotiation of the Transaction Documents.

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IN WITNESS WHEREOF, the parties hereto have caused this Convertible Note Purchase Agreement to be duly executed by their respective authorized signatories as of the date first indicated above.

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[PURCHASER SIGNATURE PAGES TO CAMBRIDGE HEART

CONVERTIBLE NOTE PURCHASE AGREEMENT ]

IN WITNESS WHEREOF, the undersigned have caused this Convertible Note Purchase Agreement to be duly executed by their respective authorized signatories as of the date first indicated above.

EIN Number: [PROVIDE THIS UNDER SEPARATE COVER]

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EXHIBIT A

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