Anomalous right ventricular muscle bundle: clinical pitfalls and extracardiac anomalies.

Seven patients with anomalous right ventricular muscle bundle are presented to emphasize possible pitfalls in the clinical diagnosis as based on physical examination, chest x ray, and electrocardiogram. Echocardiography, on the other hand, revealed abnormalities in all four of the patients on whom the study was done. The echocardiogram was directly responsible for a change in diagnosis and referral for a cardiac catheterization in one patient who had been followed for 19 years with the clinical diagnosis of a small ventricular septal defect. Four of the seven patients with anomalous right ventricular muscle bundle had extracardiac anomalies, one girl with an absent left thumb, and three patients, one girl and two boys, with left-sided renal anomalies. This high incidence of renal anomalies has not been previously reported in clinical or postmortem series.