Congenital bilateral subclavian steal: ductus-dependent symptoms in interrupted aortic arch associated with ventricular septal defect.

There are two types of congenital bilateral subclavian steal. The first type is accompanied by severe coarctation or interruption of the aorta in which both the right and left subclavian arteries have their origin distal to the obstruction in the aorta. In most cases with complete interruption of the aorta there is a large ventricular septal defect. The second, less common type of steal is associated with isolated atresia of the proximal segment of the subclavian arteries. In the first type of steal, the anatomic predisposition for the steal is present from birth but clinical symptoms frequently do not appear until childhood or adolescence. In the newborn the presence of a widely patent duclus arteriosus and its capacity to transmit the flow and pressure from a hypertensive pulmonary artery to the descending aorta and thus to the subclavian arteries prevents cerebral symptoms and angiographic signs, but in the older infant and child, the internal diameter of the ductus has usually decreased, leading to symptoms of the subclavian steal syndrome.