An infant had supraventricular tachycardia and massive anasarca at birth. The supraventricular tachycardia and congestive heart failure were minimally responsive to medical therapy. At 1 month of age, a diagnosis of atrial and ventricular septal defect was made by cardiac catheterization.
At 5 months of age, at an operation for pulmonary banding, a peculiar neoplasm of the right atrium was noted. On clamping and resection of the neoplasm, the supraventricular tachyarrhythmia reverted to normal sinus mechanism. The neoplasm, by light and electron microscopy, was thought to be a conduction system hamartoma and was thought to have caused the arrhythmia. A review of the literature showed that no such lesions had been reported previously.