Study of Cavitation in Mechanical Heart Valve Prostheses

Cavitation is believed to cause damage to tilting disk mitral mechanical heart valves (MHVs). Previous studies have indicated that this phenomenon may be dominant during MHV closure. The "squeeze-flow" field between the closing occluder and valve housing, water hammer pulse at closure and the Venturi effect are possible contributing factors. These underlying physical mechanisms have not been thoroughly investigated yet. A two phase study is proposed for systematically investigating cavitation in tilting disk MHVs using a combined experimental-nu- merical approach. During Phase I, a computer model will be developed for detailed investigation of the "squeeze-flow" effect which occurs in regions where cavitation damage has been observed in MHV explants. The valve closure velocity data, needed for these simulations, will be measured at different physiologic flow conditions in mono and bileaflet MHVs. These experiments will be performed by Dr. Ned Hwang at the University of Miami. In Phase II, a similar methodology will be used for investigating the remaining flow mechanisms that could induce cavitation. The computer models will be validated experimentally and then used to correlate the cavitation potential of tilting disk MHVs with the valve design parameters.