A Thin Film Nitinol Heart Valve
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In order to create a less thrombogenic heart valve with improved longevity, a prosthetic heart valve was developed using thin film nitinol (NiTi). A “butterfly” thin film NiTi valve was constructed using a single, elliptical piece of thin film NiTi and a scaffold made from Teflon tubing and NiTi wire. Flow tests and pressure readings across the valve were performed in vitro in a pulsatile flow loop. Biocorrosion experiments were conducted on untreated and passivated thin film nitinol. To determine the material’s in vivo biocompatibility, thin film nitinol was implanted in a pig using a stent covered with thin film NiTi. Flow rates and pressure tracings across the valve were comparable to those through a commercially available 19 mm Perimount Edwards tissue valve. No signs of corrosion were present on samples of thin film nitinol after immersion in Hank’s solution for 1 month. Finally, organs and tissue samples explanted from the pig 17 days after thin film NiTi implantation appeared without disease, and the thin film nitinol itself was without thrombus formation or endothelialization. Although long term testing will be needed, thin film NiTi may be very well suited for use in artificial heart valves.© 2004 ASME