Thrombus simulants were attached to the inflow valve housing and in-vitro sound recordings were made of mechanical aortic valves in a mock circulatory loop driven by a pulsatile artificial heart (ventricle). The valves were isolated from the ambient sound by means of a semi-anechoic chamber. Nine trials of >60 cycles each were recorded and the power spectra within 10 frequency bands (from 0 to 1000 Hz) were calculated using pole-zero modelling and Fast Fourier Transforms (FFTs) and submitted to ANOVA (analysis of variance) tests. FFT results showed a significant difference (p<0.01) in power levels within the 650 to 750 Hz band between valves with and without thrombus simulants when blockage exceeded 10% of total flow area. Pole-zero results showed a significant difference (p<0.05) when blockage exceeded 25% of total flow area.

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Conference Proceedings of the 1995 IEEE Engineering in Medicine and Biology 17th Annual Conference and 21st Canadian Medical and Biological Engineering Conference. Part 2 (of 2)
Lariviere, J., Mussivand, T., & Goubran, R. (1995). Effects of thrombus simulants on acoustic characteristics of artificial heart-valves. In Annual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings (pp. 939–940).