Isolation of the subclavian artery is an unusual anomaly in which the subclavian artery arises not from the aortic arch but from a pulmonary artery via an arterial duct. Such isolation most often occurs with a right aortic arch, and in lesions frequently associated with a right arc, such as tetralogy of Fallot. Since1994, we have undertaken surgery in four young infants with isolated subclavian arteries and unusual associated anomalies, including one with atrioventricular septal defect and common valvar orifice, two with interruption of a left aortic arch and one with interruption of a right aortic arch. In both patients with interrupted left arch, the isolated subclavian artery was diagnosed preperatively by echocardiography. We emphasize the significant issues.

We describe two children with isolated origin of the left subclavian artery from the left pulmonary artery detected by echocardiography during the assessment of their congenital cardiac malformations. Both patients demonstrated pre-operative evidence of subclavian steal. This entity results from persistence of the dorsal segment of the sixth left arch, with regression of the left fourth arch and interruption of the left dorsal arch distal to the origin of the seventh left intersegmental artery. The significance of this finding relates to the potential for pulmonary overcirculation, which could have significant post-operative ramifications if not detected prior to surgical repair of an associated cardiac malformation. This entity differs from cases with a right aortic arch and aberrant left subclavian artery which has the potential to form a vascular ring, unlike cases with isolated origin of the left subclavian artery from the pulmonary artery that do not cause compression of the airway.