Cardiovascular Fluid Mechanics: I. Fluid Dynamics of Prosthetic Aortic Valves. II. Use of the Fast Fourier Transform in the Analysis of Cardiovascular Sounds

Citation

Yoganathan, Ajit Prithiviraj (1978) Cardiovascular Fluid Mechanics: I. Fluid Dynamics of Prosthetic Aortic Valves. II. Use of the Fast Fourier Transform in the Analysis of Cardiovascular Sounds. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/TVP6-ZY22. https://resolver.caltech.edu/CaltechETD:etd-05252004-140334

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Pressure drops across ten prosthetic aortic heart valves have been measured under both steady and pulsatile flow using two different Newtonian liquids having viscosities of 0.01 dyne sec/cm[superscript 2] and 0.035 dyne sec/cm[superscript 2], respectively. The experimental results and the theory developed indicate that for a given aortic valve it is possible to predict peak systolic and mean systolic pressure drops from experimental pressure-drop data for steady flow. The difference in viscosities of the test fluids, 0.01 and 0.035 dyne sec/cm[superscript 2], seemed to have negligible effect within experimental error on the pressure drops over a range of flow rates from 83.0 cm[superscript 3]/sec to 500.0 cm[superscript 3]/sec. A laser-Doppler anemometer was used to study the in vitro velocity profiles in the near vicinity of a Starr-Edwards 1260 ball valve, a Smeloff-Cutter ball valve, a Cooley-Cutter disc valve, and a Bjork-Shiley tilting disc aortic prosthesis. The experiments were conducted under steady flow conditions. The experimental results indicate that all the aortic prostheses studied create very disturbed flow fields and cause large wall and bulk turbulent shear stresses in their near vicinity. If such stresses occur in vivo they could damage the endothelial lining of the ascending aorta, red blood cells and platelets, and could lead to thrombus formation and hemolysis. A detailed study of the Bjork-Shiley tilting disc aortic prosthesis reveals that it is possible to correlate the in vitro velocity measurements with two late pathological failure modes observed in recovered Bjork-Shiley aortic prostheses. The fast Fourier transform (FFT) was used in the frequency analysis of the first and second heart sounds in normal man, and the closing sounds of aortic prostheses produced in a pulse duplicator. An initial study indicates that frequency analysis via the FFT technique could be used as a non-invasive diagnostic tool for some cardiovascular problems.

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