We describe a patient with pulmonary atresia and intact ventricular septum in whom the right atrium was divided by a vascular aneurysm located in the right atrioventricular groove. We postulate that the structure represents an aneursymally dilated right coronary artery taking anomalous origin from the pulmonary trunk, with fistulous communication to the right atrium. We discuss the findings relative to concepts of development of the coronary arteries in normal hearts and in pulmonary atresia with an intact ventricular septum.
