Atresia of the aortic arch, with a collateral artery from the right subclavian artery supplying the descending aorta.

An infant of 2 months presented with absence of the femoral pulses, albeit with no signs of cardiac failure. The mother was known to have ingested Valproate during pregnancy. Echocardiography showed the aortic arch to be interrupted between the left common carotid and left subclavian arteries, so-called type B interruption, in the setting of an intact ventricular septum. Angiography, and multislice computed tomography, revealed the descending aorta to be supplied by a collateral artery originating from the right subclavian artery. Corrective surgery was successfully performed, but revealed an atretic segment of the arch at the site of interruption of flow.