High-Frequency Pressure Fluctuations Measured in Heart Valve Patients Peter K. Paulsen MD, Benedikte K. Jensen BSc, J. Michael Hasenkam MD, Hans Nygaard ME Mechanical heart valve patients require life-long anticoagulant therapy, in contrast to bioprosthetic valves. The reason for this is still not fully understood. In vitro studies have demonstrated the presence of cavitation bubbles in the vicinity of mechanical heart valves, but not bioprosthetic valves. When cavitation bubbles collapse they release a significant amount of energy, which also might damage the formed elements of the blood. A correlation between the presence of cavitation bubbles and high-frequency pressure oscillations has been established in vitro. The aim of this study was to measure and quantify high-frequency pressure oscillations in 20 patients with normal (n = 6), bioprosthetic (n = 5) or mechanical (n = 9) aortic valves. Measurements were performed intraoperatively using a hydrophone placed near the aortic annulus. The root mean square value (RMS) of the high-frequency pressure signals were calculated in the frequency range of 35-150 kHz. High frequency pressure fluctuations, with intensities above the noise floor, were registered only in the vicinity of mechanical heart valve prostheses, and not in the vicinity of normal or bioprosthetic valves.

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