Relation between fetal flow patterns, coarctation of the aorta, and pulmonary blood flow.

Abstract

Intracardiac anomalies cause disturbances in fetal flow patterns which in turn influence dimensions of the great vessels. At birth the aortic isthmus, which receives 25 per cent of the combinedfetal ventricular output, is normally 25 to 30 per cent narrower than the descending aorta. A shelf-like indentation of the posterior aortic wall opposite the ductus characterizes the junction of the isthmus with descending aorta. In tetralogy of Fallot, pulmonary atresia, and tricuspid atresia, when pulmonary blood flow is reduced from birth, the main pul- monary artery is decreased and ascending aorta increased in size. Conversely in intracardiac anomalies where blood is diverted away from the aorta to the pulmonary artery, isthmal narrowing or the posterior indentation may be exaggerated.