Intracardiac sound as a diagnostic adjunct in subaortic stenosis.

The purpose of this investigation is to demonstrate the potential diagnostic value of intracardiac sound recordings in patients with subaortic stenosis. Intracardiac pressure and sound were measured in 10 patients with various types of subaortic obstructions using a catheter-tip micromanometer. Seven patients had idiopathic hypertrophic subaortic stenosis (IHSS), 2 had a subvalvular membrane, and 1 had a subvalvular tunnel. Within the left ventricular cavity, at the site of maximal systolic left ventricular pressure, either there was no systolic murmur, or the murmur was of low intensity. However, within the outflow tract of the left ventricle, distal to the site of intraventricular obstruction, a prominent systolic murmur was detected in all patients. This murmur was of higher intensity than the one measured distal to the aortic valve. In one patient, in whom no subvalvular obstruction was present, but in whom entrapment of the tip of the catheter occurred, no murmur was detected in the left ventricle even though a subvalvular pressure gradient was observed. Therefore it appears that a systolic murmur recorded with maximal intensity in the outflow tract of the left ventricle may be of substantial help in distinguishing between an artifactual intraventricular pressure gradient, and one that results from intraventricular obstruction.