ABSTRACT
One family with asymmetric septal hypertrophy was reported. The propositus of this family was 31 years old man who was admitted because of transient syncope. His father and one brother were affected but asymptomatic. His sister was suddenly died at age 21 years. The interventricular septal thickness to left ventricular posterior wall thickness ratios were measured using M-mode echocard ogram. In the affected family, echocardiogram revealed asymmetric septal hypertrophy (1.5:1, 2:1, 1.9:1 respectively). In the propositus, cardiac catheterization and simultaneous biventricular cineangiography were performed. Pressure study revealed mild peak systolic pressure gradient within left ventricular apex and left ventricular outflow tract (4mm Hg respectively). Biventricular cineangiogram showed the septal width increased inferiorly, and left ventricular endocardial surface of the septum was straight, while the right ventricular border convex toward the right ventricle.