Persistent left fifth aortic arch in man. Report of two cases.

Two cases ofpersistent leftfifth aortic archforming a congenital double lumen aortic arch have been confirmed at necropsy. In the first case, the diagnosis was suspected during life after aortography. An unusual vessel ran inferior and parallel to the aortic arch from the innominate artery to the left subclavian artery. It lay superior to the pulmonary artery. Both cases were associated with other cardiovascular anomalies. The first case had a persistent ductus arteriosus, and a small membranous ventricular septal defect; the second, coarctation of the aorta, persistent ductus arteriosus, bicuspid aortic valve, and a single right coronary artery. There is disagreement about the existence of the fifth aortic arch in man. In the cat embryo, Hunting-ton (I9I9) depicts a fifth arch forming a vascular channel beneath the fourth arch. Brown (I9I3) in the cat embryo, and Buell (I922) in the chick embryo have described the existence of the fifth arch. Congdon (1922) reported that endothelial sprouts arising from the aortic sac ventrally and from the descending thoracic aorta correspond to the upper and lower ends of the fifth arches in man. (I962) allege that the status of the fifth aortic arches is uncertain. Balinsky (i965), Arey (i965), Langman (i969), and Duckworth (I967) either deny the existence of the fifth aortic arch in mammals, or believe that it is only present transiently if it does exist. Van Praagh and Van Praagh (I969) described the first case of duplication of the aortic arch and suggested that the smaller caudal arch or 'subway' represented the fifth aortic arch. In this presentation , we describe, to the best of our knowledge, the first case of a persistent fifth aortic arch diagnosed during life and a third example of this rare malformation in which there were two complete aortic arches of almost equal size arising anterior to the trachea. after an assisted breech delivery. The Apgar score was I. Intensive resuscitation was necessary. Initially, clinical findings and chest x-ray were compatible with the diagnosis of respiratory distress syndrome. Respiratory difficulty persisted, and from the end of the first week she required assisted ventilation by intermittent positive pressure. She also had convulsions due to hypogly-caemia and hypocalcaemia.