Muscular Subaortic Stenosis in Childhood

The clinical findings in three siblings with muscular subaortic stenosis are presented, showing the progression of this disease entity within the pediatric age group. In two of the children the diagnosis was supported by hemodynamic findings, supplemented by surgical and autopsy observations in one of these cases. In the youngest member of the family group the diagnosis is based on the clinical examination, thoracic roentgenograms, and electro-vector-cardiographic evidence of left ventricular hypertrophy. It is probable that the father and paternal grandfather died of the same disease. Approximately one-half of the reported cases of this lesion have been familial, supporting the concept that this disease is transmitted by a dominant Mendelian gene. Slowly progressive fatiguability with exertion, palpitations, angina, and syncope are the most frequent symptoms. Congestive heart failure is rare, but sudden unexpected death is common. A harsh systolic ejection murmur at the left sternal border and apex is a constant physical finding; this is often accompanied by paradoxical splitting of the two components of the second heart sound. Chest roentgenograms demonstrate progressive left ventricular hypertrophy and a normal-sized aorta. The electrocardiogram and vectorcardiogram usually show left ventricular hypertrophy, often accompanied by negative T-waves in the left precordial leads. Characteristic hemodynamic findings are a distinctive pulse contour, the narrowing of the peripheral arterial pulse pressure following a premature ventricular contraction, and a pressure gradient between the body and outflow tract of the left ventricle. Left ventricular angiocardiography shows a narrowing of the muscular obstruction during systole and a widening during diastole. Excision of this muscular obstructive lesion has been reported to produce marked symptomatic relief in some patients.