Hypertrophic cardiomyopathy. Disappearance of auscultatory, carotid pulse, and echocardiographic manifestations of obstruction following myocardial infarction.

Three patients with echocardiographically documented asymmetric septal hypertrophy and findings compatible with dynamic left ventricular outflow tract obstruction suffered acute myocardial infarction in regions remote from the interventricular septum. Following infarction, echocardiographic signs of dynamic left ventricular outflow tract obstruction were no longer apparent. No resting gradient was documented in either of the two patients undergoing cardiac catheterization following myocardial infarction. Valsalva's maneuver resulted, however, in a gradient of 20 mm Hg in one patient. It appears that myocardial infarction may cause loss of or marked lessening of dynamic left ventricular outflow tract obstruction, even when the infarction involves areas other than the septum.