Muscular Subaortic Stenosis

A quarter of a century has passed since Brock's original report1 of the condition characterized by asymmetric septal hypertrophy and a subaortic pressure gradient (muscular subaortic stenosis).2 The pressure gradient may be affected by changes in myocardial contractility, systemic vascular resistance, and ventricular volume.3 Propranolol has little effect on the pressure gradient at rest, but it may diminish the increment that occurs with exercise.4 Verapamil has a greater effect than propranolol in reducing the gradient at rest, although substantial gradients (>50 mm Hg) have persisted even after high doses of intravenous verapamil, and in one patient the gradient markedly increased. . . .