Transient asymmetric ventricular septal hypertrophy in the newborn unassociated with maternal diabetes.

Severe hypertrophy of the interventricular septum was found by echocardiography in a 15 day old infant without symptoms whose mother was not diabetic. The electrocardiogram showed pronounced intraventricular conduction disturbances. Both echocardiographic and electrocardiographic findings showed no abnormality after 27 months, the explanation for which could be the spontaneous regression of an intracardiac rhabdomyoma.