Association of interrupted aortic arch with malformations producing reduced blood flow to the fourth aortic arches.

Interrupted aortic arch is a rare congenital malformation of the great arteries with loss of continuity between the proximal portion of the aortic arch and the descending aorta, which is usually supplied by a patent ductus arteriosus. The hearts of 12 patients with interrupted aortic arch listed in the autopsy files of The Johns Hopkins Hospital were evaluated. Four categories were identified. Seven hearts with normal outflow tract relations had significant pulmonary arterial override of a ventricular septal defect and thus recevived part of left ventricular and all of right ventricular ejection flow; flow into the aorta was correspondingly reduced. Two hearts had mitral valve obstruction with decreased left heart flow. Two hearts had double inlet left ventricle and transposed great arteries with the aorta originating from a small anterior conal chamber. One heart had a truncus malformation with a disproportionately large flow entering the pulmonary arterial division. In each of these hearts, the pattern of the outflow tracts and associated malformations suggested that there was a preferential flow of blood into the sixth arches and correspondingly a reduced flow into the fourth arches at the time of normal disappearance of components of the embryonic aortic arch system. Thus, interrupted aortic arch may simply be disappearance of the normally persisting connection between the left fourth and sixth arches as a result of flow imbalance in early cardiogenesis.