The effect of the aortic valve orientation on cavitation.

When implanting a mechanical aortic valve the annulus orientation is important with respect to turbulence. However, the effect on cavitation has not yet been investigated. The aim of this study was to investigate how cavitation is influenced hereof in vivo. Three pigs were included in the study. An Omnicarbon 21mm valve equipped with a rotating mechanism enabling controlled rotation of the valve was implanted in aortic position. Under stable hemodynamic conditions, measurements were performed using a hydrophone positioned at the aortic root. The valve was rotated from 0-360° in increments of 30°. From the pressure fluctuations recorded by the hydrophone the root mean square of the 50 kHz high pass filtered signal as well as the non-deterministic signal energy was calculated as indirect measures of cavitation. Various degrees of cavitation were measured but no relationship was found between either of the two cavitation measures and the valve orientation. Hemodynamics varied during the experiments for all pigs (3.9-5.7 l/min; 5.0-7.2 l/min; 3.1-7.5 l/min). Changes in cavitation quantities seemed to be caused by changes in hemodynamics rather than valve angular position. In conclusion, these results do not favor any position over another in terms of cavitation potential.