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TECHNICAL PAPERS

A Thin Film Nitinol Heart Valve

[+] Author and Article Information
Lenka L. Stepan

Biomedical Engineering Department, University of California at Los Angeles, Room 32-135, Engineering IV, Los Angeles, CA 90095lenka@seas.ucla.edu

Daniel S. Levi

Pediatric Cardiology, Mattel Children’s Hospital at UCLA, B2-427, 10833 Le Conte Avenue, Los Angeles, CA 90095-1743dlevi@ucla.edu

Gregory P. Carman

Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, 38-137M Engineering IV, Los Angeles, CA 90095carman@seas.ucla.edu

J Biomech Eng 127(6), 915-918 (Jul 06, 2005) (4 pages) doi:10.1115/1.2049311 History: Received March 20, 2005; Revised June 23, 2005; Accepted July 06, 2005

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” 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. Bio-corrosion experiments were conducted on untreated and passivated thin film nitinol. To determine the material’s in vivo biocompatibility, thin film nitinol was implanted in pigs using stents 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 thin film nitinol samples after immersion in Hank’s solution for one month. Finally, organ and tissue samples explanted from four pigs at 2, 3, 4, and 6 weeks after thin film NiTi implantation appeared without disease, and the thin film nitinol itself was without thrombus formation. Although long term testing is still necessary, thin film NiTi may be very well suited for use in artificial heart valves.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Inner Teflon tubing with support bars

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Figure 2

Closed (left) and open (right) positions of a completed thin film nitinol butterfly valve

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Figure 3

Flow rates from the butterfly valve were similar to that of the Edwards valve and significantly higher than without a valve

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Figure 4

Pressure traces from (a) no valve, (b) Edwards tissue valve, and (c) thin film nitinol butterfly valve in pulsatile pump

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Figure 5

Left: Liver, Right: Lung. Histology pictures of organs after aortic thin film nitinol implantation in pig.

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Figure 6

Stainless steel stent covered with thin film nitinol after two weeks of implantation. The left half on the stent is bare and displays tissue growth. The right side of the stent is covered with thin film nitinol and is free of tissue growth.

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Figure 7

Left A: Damage on aorta wall from bare stent strut. Left B: Neointimal formation where bare stent contacted aorta wall. Right: Healthy aortic wall where thin film nitinol covered stent was placed.

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Figure 8

The piece of thin film nitinol shown on the left is free from tissue growth. An SEM picture of the same film (right) reveals only RBC’s are found on the surface of the thin film nitinol after the film was explanted from a pig.

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