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TECHNICAL PAPERS

Cavitation Dynamics of Medtronic Hall Mechanical Heart Valve Prosthesis: Fluid Squeezing Effect

[+] Author and Article Information
C. S. Lee

University of Iowa, Iowa City, IZ 52242

K. B. Chandran

Departments of Biomedical and Mechanical Engineering, University of Iowa, Iowa City, IA 52242

L. D. Chen

University of Iowa, Iowa City, IA 52242

J Biomech Eng 118(1), 97-105 (Feb 01, 1996) (9 pages) doi:10.1115/1.2795951 History: Received July 21, 1993; Revised December 04, 1994; Online October 30, 2007

Abstract

The cause of cavitation in mechanical heart valves is investigated with Medtronic Hall tilting disk valves in an in vitro flow system simulating the closing event in the mitral position. Recordings of pressure wave forms and photographs in the vicinity of the inflow surface of the valve are attempted under controlled transvalvular loading rates averaged during valve closing period. The results revealed presence of a local flow field with a very high velocity around the seat stop of mechanical heart valves that could induce pressure reduction below liquid vapor pressure and a cloud of cavitation bubbles. The analysis of the results indicates that the “fluid squeezing” between the stop and occluder as the main cause of cavitation in Medtronic Hall valves. The threshold loading rate for cavitation initiation around the stop was found to be very low (300 and 400 mmHg/s; half the predicted normal human loading rate that was estimated to be 750 mmHg/s) because even a mild impact created a high speed local flow field on the occluder surface that could induce pressure reduction below vapor pressure. The present study suggests that mechanical heart valves with stops at the edge of major orifice region are more vulnerable to cavitation, and hence, have higher potential for damage on valve components and formed elements in blood.

Copyright © 1996 by The American Society of Mechanical Engineers
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