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ASAIO CARDIAC ABSTRACT

CAVITATION INTENSITY RANKING OF THE MECHANICAL HEART VALVES BASED ON THE FAINT LIGHT OBSERVATION

Takiura, K1; Chinzei, T1; Imachi, K1

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Cavitation on mechanical heart valves (MHVs) has been identified as a cause of MHV failure. A reliable in vitro test method to evaluate the cavitation potential has been investigated since the early 1990s. We are developing the evaluation method of cavitation based on sonoluminescence. The cavitation bubbles emit the faint light at their collapse. Then the bubble collapse, which actually induces harmful effects, was analyzed by counting the photons emitted from the cavitation bubbles around the MHV. A photon counting system was developed using a photomultiplier tube. The MHV closure triggered the photon counter. The photons were recorded for 3.5 msec from MHV closure every beat, and they were accumulated over 500 beats. In addition to a 20-mm Björk-Shiley as a reference specimen, the FDA Round Robin 27-mm MHVs (Medtronic Hall, Edwards Duromedics and St Jude Medical) were investigated. The valve was submerged in the water tank of 9-L deionized water, and the pressure difference of 120 and 200 mmHg was exerted on the valve at 60 bpm with a pulse duplicator. The ratio of the photon number for a MHV specimen to that for the reference Björk-Shiley against 120 mmHg was defined as the cavitation intensity. Cavitation intensities of Björk-Shiley, Medtronic Hall, Edwards Duromedics and StJude Medical were1, 0.51, 0.15 and 0.01 against 120 mmHg, and 1.81, 0.88, 0.21 and 0.01 against 200 mmHg, respectively. The cavitation intensity was successfully quantified and it was clearly demonstrated that bileaflet MHVs elude violent cavity collapse. We believe this method would he acknowledged for gauging the MHV cavitation severity.

Copyright © 2004 by the American Society for Artificial Internal Organs