Biomedical Engineering Reference
In-Depth Information
4.17 Abiocor artifi cial heart with trileafl et Angiofl ex valve (arrow).
Image courtesy of Abiomed, Danvers, MA, USA.
surfaces they contact will facilitate development of materials with
improved blood compatibility. Ceramics-based products are especially
durable and stable because ceramic materials minimize surface-induced
activation and are highly resistant to chemical modifi cation and mechani-
cal damage. 104 One such design incorporates a single crystal alumina disc
and a titanium nitride (TiN) valve ring. Electron microscopy studies
showed the device was free of platelet aggregation or fi brin deposition,
and high pressure testing revealed better than expected durability. 105 Other
alloplastic biomaterials are being investigated, including silicone and other
plastics, based on the success of other plasticized medical devices. 106
Silastic-polyurethane (Angiofl ex®), a biomaterial developed by Abiomed
(Danvers, MA, USA), has been incorporated into the Abiocor® artifi cial
heart (Fig. 4.17). 107,108
The Abiocor® valve is designed as a trileafl et confi guration without
seams. In vitro fl uid dynamic testing revealed an overall improvement in
performance as compared with the Carpentier-Edwards and Ionescu-
Shiley tissue valves. However, steady and pulsatile fl ow velocity measure-
ments with a laser Doppler anemometer system indicated a jetlike and
turbulent fl ow fi eld downstream of the valve. 109 Scanning electron micros-
copy of the Angiofl ex valve 29 days after implantation revealed some
structural deterioration on the closing edge of the valve and platelet adhe-
sion, but no major thrombi were noted. 110 Antimicrobial coatings of the
Abiocor® valve also have been tested, but impregnating the valve with
chlorhexidine digluconate produced no additive or synergistic antibacte-
rial effect as compared to uncoated valves. 111 Angiofl ex valves with Dacron
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