A novel study of mechanical heart valve cavitation in a pressurized pulsatile duplicator

Submission of data regarding the cavitation potential of a mechanical heart valve is recommended by the U.S. Food and Drug Administration in the device-review process. An acoustic method has long been proposed for cavitation detection. However, the question as to whether such a method can differentiate the cavitation noise from the mechanical closing sound has not been sufficiently addressed. In this study, cavitation near a Medtronic Hall tilting disc valve was investigated in a pressurized pulsatile duplicator. The purpose of pressurizing the testing chambers was to prevent cavitation under a normally cavitating loading condition to isolate the mechanical closing sound. By comparing the sound signals before and after pressurization, some noticeable differences were found between them. In the time domain, the intensity of the sound under a cavitating condition was much higher. In the frequency domain, the energy distribution of a sound signal was distinctively different depending on whether cavitation occurred or not. The valve closing sound had a large amount of energy in the low-frequency range (less than about 25 kHz). When cavitation took place, the sound energy shifted toward the high-frequency range (from 25 to 500 kHz).