Genesis of the systolic murmur of idiopathic hypertrophic subaortic stenosis. Phonocardiographic, echocardiographic, and pulsed Doppler ultrasound correlations.

To study the genesis of the systolic murmur of idiopathic hypertrophic subaortic stenosis (IHSS), phonocardiograms, echocardiograms, and pulsed Doppler echocardiography were done in 11 patients with IHSS. Seven had marked systolic anterior motion of the mitral valve (SAM) at rest (group 1); four had small SAM at rest but marked SAM was noted after amyl nitrite inhalation, (group 2). In all group 1 patients, marked turbulence was present during systole in the left ventricular outflow tract (LVOT). A lesser degree of turbulence was present in systole in the left atrium in six of seven patients. The turbulence in the LVOT and left atrium was increased by amyl nitrite, and decreased by handgrip. In group 2 patients, mild turbulence was present in the LVOT at rest, but none was noted in the left atrium. Amyl nitrite increased turbulence in the LVOT, and turbulence in the left atrium was noted in two patients. We conclude that the murmur of IHSS in patients with marked SAM is due to a composite of turbulence in the LVOT and mitral regurgitation, whereas when only mild SAM is present, the murmur originates in the left ventricular outflow tract.