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Abstracts: ASAIO Bioengineering/tissue Engineering Abstracts


Wu, Changfu1; Liu, Jia-Shing2; Hwang, Ned H C2; Lin, Yukweng M1

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Mechanical heart valves (MHVs) are among the most successful artificial implants in clinical use today. Driven by the transvalvular pressure difference, an MHV opens and closes through fluid-structure interaction. From both structure and fluid dynamics point of views, the closing phase imposes more severe loading conditions on the valve leaflet(s) and the surrounding blood, such as water hammer effect, negative pressure drop, and high shear stress, all of which are undesirable properties associated with an MHV.


A two-dimensional computational fluid dynamics analysis was performed to simulate the closing process of a 25 mm St. Jude Medical bileaflet MHV, by means of a fully-coupled fluid-structure-interaction approach. A loading rate of 750 mmHg/s was applied on the ventricular side.


The simulation results are generally in good agreement with previous experimental observations. The leaflet closes in about 22 ms with a maximum tip velocity of 1.97 m/s. Upon closure, the leaflet undergoes elastic deformation and the leaflet tip decelerates rapidly. It is noted that the peak negative pressure on the atrial side of the leaflet tip occurs during the leaflet deceleration phase. When the leaflet tip approaches the inner surface of the housing, a leakage jet is formed in the peripheral clearance gap, which accelerates to about 14 m/s as a result of both a narrowing clearance gap and the regional negative pressure field on the atrial side. The maximum shear stress thereby reaches 4000 Pa. The water-hammer force exerted on the leaflet is about 12 N.

Copyright © 2005 by the American Society for Artificial Internal Organs