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The movements of the mitral, tricuspid and aortic valves have been recorded echocardiographically and related to the first heart sound (S1) in patients with various hemodynamic and conduction abnormalities. Closure of the mitral and tricuspid valves has been studied with respect to the corresponding atrioventricular pressure crossover and it is clear that both valves finish closing about 50 msec after pressure crossover. In order to clarify the relative contribution of tricuspid valve closure and aortic root events to the second high frequency component of S1, a new simultaneous dual echophonocardiographic technique was employed. This permitted the simultaneous registration of tricuspid and aortic valve movements and demonstrated that in certain circumstances the second high frequency component of S1, could be attributed to tricuspid closure, aortic root events being excluded from the genesis of this sound. These observations suggest that the two high frequency components of S1 are related to closure of the mitral and tricuspid valves. The results do not however, exclude a contribution to S1 of aortic root events, which may be of lower frequency vibrations.

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