Auscultatory features of hypertrophic obstructive cardiomyopathy. A study of 90 patients.

The auscultatory signs in 90 subjects with hypertrophic obstructive cardiomyopathy are described. The late-onset ejection systolic murmur and its responses to vaso-active manoeuvres reflect a volume-dependent outflow tract obstruction. Late vibrations of the systolic murmur, not uncommonly recorded at the apex, are due to associated mitral incompetence. Non-ejection systolic clicks may occur, and the likely explanation is inequality of the functional length of the mitral chordae tendineae secondary to asymmetrical myocardial hypertrophy. The second heart sound is often abnormal, usually with delay in the aortic component. Some correlation was demonstrated between the relative degrees of left and right ventricular outflow obstruction and the pattern of splitting of the second heart sound. Reversed or partially reversed splitting is usually associated with a more severe left ventricular outflow obstruction. Ejection systolic clicks and early diastolic murmurs occur infrequently, but are not incompatible with the diagnosis of hypertrophic obstructive cardiomyopathy.