IN-VIVO OBSERVATION OF CAVITATION ON PROSTHETIC HEART-VALVES

In this study, a method to determine the existence of prosthetic heart valve cavitation in vivo is presented. Pennsylvania State University Left Ventricular Assist Devices (LVADs) were implanted in two separate calves for this study. Bjork-Shiley Monostrut (Irvine, CA) 27 mm and 25 mm valves with Delrin occluders were used in the mitral and aortic positions, respectively. A high fidelity, piezoelectric pressure trans ducer was mounted approximately 1.25 cm proximal to the mitral valve a nd measured the high frequency pressure fluctuations caused by cavitat ion bubble formation and collapse after valve closure. The root mean s quare (RMS) value of the mitral pressure signal during a 5 ms interval after valve closure was used as a measure of cavitation intensity. Th e pressure signals observed in vivo were similar to ones observed in v itro with the same type of pressure transducer and were associated wit h the visually observed cavitation. The percentage of beats with cavit ation increased from 20.3% to 67.7% when pump filling was decreased by increasing beat rate. A blood test conducted during post-operative da ys 1-3 showed a significant increase in plasma hemoglobin during the l ow filling condition. However, blood tests conducted later (post-opera tive days 7-44) did not show a significant change in plasma hemoglobin during low filling conditions.