INVESTOR CONTACT:
- -----------------
John F. Thero
Chief Financial Officer
(978) 777-5410

MEDIA CONTACT:
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Edward E. Berger, Ph.D.
Vice President for Government and External Affairs
Corporate Communications
(978) 777-5410

FOR IMMEDIATE RELEASE

             ABIOMED OUTLINES OFFER TO ACQUIRE THERMO CARDIOSYSTEMS

         DANVERS, MA, January 9, 2001--ABIOMED, Inc. (NASDAQ: ABMD), a leader in
heart assist and replacement technology, confirmed today that it has made an
offer to acquire Thermo Cardiosystems, Inc. (AMEX: TCA) of Woburn, MA. Thermo
Cardiosystems is a manufacturer and developer of left ventricular assist
systems. ABIOMED's offer for Thermo Cardiosystems is a fixed $11.50 per share,
with $1.50 in cash and $10.00 in ABIOMED common stock, subject to a cap on the
maximum number of shares offered.

         "We believe that our offer is superior to the current arrangement of
Thermo Cardiosystems to merge with Thoratec Laboratories Corporation." stated
Dr. David M. Lederman ABIOMED's President and Chief Executive Officer.
"ABIOMED's offer provides an exciting alternative to Thermo Cardiosystems with a
company in ABIOMED that doesn't have overlapping or directly competing product
lines."

         "ABIOMED has established market leadership with its BVS(R) product
line. We have brought the AbioCor(TM) Implantable Replacement Heart to the
threshold of clinical trials. We are in a very solid financial position. As
part of our growth strategy, we will selectively look to acquire
complementary products and companies that would help us better serve our
customers. Joining ABIOMED with TCA would provide powerful synergies and
growth opportunities" Dr. Lederman said. "ABIOMED has unique technology and
experience that we believe would improve Thermo Cardiosystems' products. The
resulting company would offer a broad range of best-in-class products for the
full spectrum of clinical indications from short-term recovery assistance to
total heart replacement."

         "ABIOMED and Thermo Cardiosystems share many common customers. Our
customers have been outspoken in recent months regarding the attractiveness of
adding Thermo Cardiosystems to ABIOMED. We are convinced that together we would
provide greater levels of customer support, greater product options, introduce
new products faster and continually improve our existing products with the
combined resources and experiences of our two companies. Given the large need
for heart assist and replacement technology, our respective commitment and focus
in these areas and our extensive technology and experience, we are


convinced that a combination of ABIOMED and Thermo Cardiosystems at the right
price is in the best interest of our customers, shareholders and employees,"
stated Dr. Lederman.

         "The missions, histories and prospects of ABIOMED and Thermo
Cardiosystems are compelling and remarkably consistent with one another," added
Dr. Lederman. "Just as ABIOMED is positioned to be first to market with an
implantable replacement heart, Thermo Cardiosystems is a leader with products
for other exciting emerging niche markets. We have great respect for the people
at Thermo Cardiosystems. Both companies are focused on solutions for the many
needs of heart failure patients. Both companies are pioneers in the area of
heart assist devices. Both companies have decades of experience and know-how
together with extensive technology that we believe are unmatched in the
industry. Both companies currently market ventricular assist devices for
temporary patient support. ABIOMED was first to market with a bridge to recovery
device, our BVS system. Thermo Cardiosystems was first to market with a bridge
to transplant device, the Heartmate. The BVS and Heartmate are the current
market leaders in their respective markets, each with more customers and
patients supported than any other ventricular assist device. Both ABIOMED and
Thermo Cardiosystems are working towards application of our respective
technologies into new and larger markets. Thermo Cardiosystems is currently
conducting a clinical trial of its device for the permanent support of patients
needing ventricular assistance with a focus on congestive heart failure
patients. ABIOMED is preparing for a clinical trial of its implantable
replacement heart for the permanent support of patients needing ventricular
replacement with focus on coronary heart disease patients and those congestive
heart failure patients who cannot be adequately assisted by a ventricular assist
device. These two separate markets for permanent support of end-stage heart
failure patients we estimate to each be multi-billion dollar annual
opportunities."

         "The combination of the companies would result in a company that is
well capitalized, with over $100 million in cash, and with over $90 million in
annual revenues. The combined company would have broad distribution capabilities
and an extensive pipeline of products in research and development. We see
opportunities for extensive leverage from these synergies" said ABIOMED's Chief
Financial Officer John F. Thero.

         "Our offer is before the Thermo Cardiosystems' Board. If they choose to
forego their present arrangement, we are prepared to act quickly and decisively
to reach an agreement and complete this proposed transaction" said Mr. Thero.
"We are optimistic about ABIOMED's future. If our proposal were to be accepted,
the closing of the transaction may benefit from the timing and momentum of our
AbioCor Implantable Replacement Heart. Merging with Thermo Cardiosystems would
add diversity and additional upside potential to ABIOMED without straying from
our areas of core competency. If we can reach an agreement, we would not
anticipate regulatory difficulties. Furthermore, post-merger integration would
be facilitated because both companies are headquartered here in Massachusetts;
geographic proximity would help us deal effectively with communication and
coordination issues, and work force relocation would be minimal." ABIOMED
expects that it would retain substantially all of Thermo Cardiosystems'
employees and management.

         Based in Danvers, Massachusetts, ABIOMED, Inc. (pronounced
"AB'-EE-O-MED") is a leading developer, manufacturer and marketer of medical
products designed to assist or replace


the pumping function of the failing heart. The Company's AbioCor implantable
replacement hearts is in advanced stages of development and the AbioCor is
awaiting FDA approval to begin initial human trials. ABIOMED currently
manufactures and sells the BVS, a temporary heart assist device, for the support
of all patients with failing but potentially recoverable hearts. This News
Release contains forward-looking statements, including statements regarding the
expected benefits of the proposed merger, the development of and timing of new
products and revenue growth potential. Actual results may differ materially
based on a number of factors, including uncertainty of successfully meeting
product development milestones and obtaining regulatory approvals for clinical
trials, complex manufacturing, unproven markets for products under development,
dependence on key personnel, competition and technological change, uncertainty
in the ability to recruit required personnel on a timely basis, government
regulations, dependence on limited sources of supply, dependence on third-party
reimbursement, potential inadequacy of product liability insurance, dependence
on patents and proprietary rights and other risks detailed in the Company's
filings with the Securities and Exchange Commission. There can be no assurance
that the Company's offer would be accepted or, if accepted, approved by
regulatory authorities and shareholders. Investors are cautioned that all such
statements involve risks and uncertainties. Readers are cautioned not to place
undue reliance on these forward-looking statements, which speak only as of the
date of this Release. The Company undertakes no obligation to publicly release
the results of any revisions to these forward-looking statements that may be
made to reflect events or circumstances after the date hereof or to reflect the
occurrence of unanticipated events.

         This material is not a substitute for the proxy statement/prospectus
included in the registration statement which would be filed with the Securities
and Exchange Commission by ABIOMED in connection with this proposed business
combination with Thermo Cardiosystems. Investors are urged to read any such
proxy statement/prospectus because it will contain important information,
including detailed risk factors. The registration statement that would be filed
by ABIOMED, as well as the proxy statement/prospectus and other documents filed
with the SEC by ABIOMED, will be available free of charge at the SEC's website
(www.sec.gov) and from ABIOMED.

         ABIOMED, its directors and certain of its executive officers may be
considered participants in any solicitation of proxies made in connection with
the proposed business combination. Information concerning ABIOMED's directors
and executive officers can be found in the documents filed or to be filed with
the SEC, including any such proxy statement/prospectus.