SOUNDS DUE TO MUSCULAR CONTRACTION AND THEIR IMPORTANCE IN AUSCULTATORY QUALITIES OF THE FIRST HEART SOUND

Abstract

The question as to whether skeletal muscle of frogs and isolated portions of the cats'' ventricles give rise to sounds when contracting under varying degrees of isometricity was re-investigated by registering vibrations from such muscles. For this purpose the Wiggers-Dean capsules were so modified as to increase their sensitivity, decrease their periodicity and enhance the stability of the rubber cement film. Sound vibrations could be heard and recorded from such preparations provided that a minimal degree of shortening occurs. The number, amplitude and duration of these vibrations depended on the vigor of contraction and the degree of shortening permitted. The investigations were then extended to registration of vibrations from the anterior surface of the dog''s ventricles before and after ligation of the ramus descendens. This enabled a comparison of sound vibrations from a region that is first contracting and then passively stretched during systole. No significant changes could be detected as long as intraventricular pressure curves remained essentially unchanged as to gradients and magnitude. It is concluded that vibrations produced directly by contraction are probably obscured or submerged by the more intense vibrations of other structures and that they are related most definitely to changes in intraventricular tension. Consequently there seems little probability that alterations in recorded first sounds can be of help in the diagnosis of coronary infarction.