Phonocardiography, in conjunction with external pulse tracings, can often be decisive in the diagnosis of idiopathic hypertrophic subaortic stenosis (IHSS). This disease has been recognized with considerable frequency in recent years,1 and it is incumbent upon the clinician to familiarize himself with its various manifestations.
Idiopathic hypertrophic subaortic stenosis is characterized by hypertrophy of the entire left ventricle with particular involvement of the interventricular septum in the region of the outflow tract. Subaortic obstruction is a dynamic process, and the stenosis occurs only after the left ventricle has contracted sufficiently to bring into approximation the thickened walls of its outflow tract. For this reason, the stenosis may vary in severity from time to time, and maneuvers which increase the vigor of ventricular contraction or which enhance left-ventricular emptying will increase the subaortic obstruction.
As a result of the subaortic stenosis, a midsystolic, crescendodecrescendo (diamond-shaped) murmur is produced which is
Tavel ME. Clinical Phonocardiography: III. Its Use in Diagnosis of Idiopathic Hypertrophic Subaortic Stenosis. JAMA. 1968;203(4):285–286. doi:10.1001/jama.1968.03140040037009
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