Reversal of left carotid arterial flow as a sign of type C interruption of the aortic arch.

While performing neurosonography on an 8-day-old baby boy, we noted antegrade flow in the right carotid and basilar arteries but retrograde flow in the left carotid artery. The child was diagnosed as having a severe cardiac malformation and associated interruption of the aortic arch on echocardiography. Our finding is explained by the site of interruption-between the innominate and left carotid arteries, or type C interruption.