A rare heart defect characterized by complete lack of anatomical continuity between the transverse aortic arch and the descending thoracic aorta. AAI should be distinguished anatomically from atresia of the aortic arch where continuity between these segments is achieved by an imperforate fibrous strand of various lengths.

In utero, the ductus arteriosus (DA) serves to divert ventricular output away from the lungs and toward the placenta by connecting the main pulmonary artery to the descending aorta. A patent ductus arteriosus (PDA) in the first 3 days of life is a physiologic shunt in healthy term and preterm newborn infants, and normally is substantially closed within about 24 hours after bith and completely closed after about three weeks. Failure of physiologcal closure is referred to a persistent or patent ductus arteriosus (PDA). Depending on the degree of left-to-right shunting, PDA can have clinical consequences.