Pulmonary blood supply by a branch from the distal ascending aorta in pulmonary atresia with ventricular septal defect: differential diagnosis of fifth aortic arch.

A patient with pulmonary atresia and a ventricular septal defect is described in whom an arterial branch from the distal ascending aorta supplied segments of both lungs. The branch is considered to represent a persistent fifth aortic arch. The possible morphogenesis and differential diagnosis of a communication between the ascending aorta and the pulmonary artery in pulmonary atresia with ventricular septal defect are discussed.