Acoustic and visual characteristics of cavitation induced by mechanical heart valves.
OBJECTIVE
A sudden pressure drop and recovery can induce cavitation in liquids. Mechanical heart valves (MHVs) generate such a pressure drop at closure, and cavitation generation around MHVs has been demonstrated many times. Cavitation is suspected as being a cause of blood and valve material damage.


METHODS
In this in-vitro experiment, visual images and acoustic signals associated with MHV cavitation were studied to reveal cavitation characteristics. Björk-Shiley Convex-Concave valves, one with a pyrolytic carbon occluder and one with a Delrin occluder, were installed in a single-shot valve chamber. Cavitation intensity was controlled by load (dP/dt) and air content of water. The acoustic signal was measured using a hydrophone and visual images recorded with a high-speed digital camera system.


RESULTS
Cavitation images showed that 10 ppm water rarely developed cavitation, unlike the 16 ppm water. A distinct peak pressure was observed at cavitation collapse that was a good indicator of MHV cavitation intensity. The average of the peak pressures revealed that cavitation intensity increased faster with increasing load for the 16 ppm water.


CONCLUSIONS
The use of the peak pressure may be the preferred method for correlating cavitation intensity in structures for which the separation of valve closure noise and cavitation signal is difficult, as for the valves studied here.
Sohn
Kwanghyun
K
The Pennsylvania State University, Department of Bioengineering, 205 Hallowell Building, University Park, PA 16802, USA.
Manning
Keefe B
KB
Fontaine
Arnold A
AA
Tarbell
John M
JM
Deutsch
Steven
S
D000162:Acoustics; D001672:Biocompatible Materials; D002244:Carbon; D006350:Heart Valve Prosthesis; D018056:Hemorheology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008422:Materials Testing; D008955:Models, Cardiovascular; D010781:Photography; D011312:Pressure; D011474:Prosthesis Design; D012117:Resins, Synthetic; D012815:Signal Processing, Computer-Assisted; D014867:Water
D001672:Biocompatible Materials; D012117:Resins, Synthetic; C009139:pyrolytic carbon; D014867:Water; D002244:Carbon; C010102:delrin