Two broadband components were observed the first coincided with mitral valve closure while the second significantly preceded aortic valve opening. The most dominant feature was a powerful, rapidly-rising frequency component that preceded mitral valve closure. The first heart sound was observed to be non-stationary and multicomponent. Heart sounds were recorded using ultralight acceleration transducers cemented directly to the epicardium. A resonant origin for first heart sound generation was tested through two studies in an open-chest canine preparation. Accordingly, the goals of this thesis were threefold, (1) to characterize the frequency dynamics of the first heart sound, (2) to determine the relative contribution of the myocardium and the valves in determining first heart sound frequency, and (3) to develop new tools for non-stationary signal analysis. Previous clinical studies have implicated resonant vibrations of both the myocardium and the valves. The results showed that the relationships are best fit by nonlinear exponential models.įrequency Dynamics of the First Heart SoundĬardiac auscultation is a fundamental clinical tool but first heart sound origins and significance remain controversial. The relationship between the maximum amplitude of S1 and the maximum rising rate of LVP and the relationship between the amplitude of dominant peaks/valleys and the corresponding rising rate of LVP were examined by linear, quadratic, cubic, and exponential models. To further investigate this relationship, this study simultaneously sampled the external phonocardiogram, electrocardiogram, and intracardiac pressure in the left ventricle in three anesthetized dogs, while invoking wide hemodynamic changes using various doses of epinephrine. Some researchers believed the relationship was positively linear others stated the relationship was only positively correlated. The relationships between the amplitude of the first heart sound (S1) and the rising rate of left ventricular pressure (LVP) concluded in previous studies were not consistent. Tang, Hong Ruan, Chengjie Qiu, Tianshuang Park, Yongwan Xiao, Shouzhong Reinvestigation of the relationship between the amplitude of the first heart sound to cardiac dynamics.
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