Association of distal displacement of the left subclavian artery and coarctation of the aorta.

Previously noted but undocumented observation of distal displacement of the left subclavian artery in patients with discrete coarctation of the aorta was verified by an objective two-dimensional echocardiographic method in 28 patients with aortic coarctation and in 43 control subjects. Relative position of brachiocephalic arteries to one another was evaluated by the ratio of the distance between the left common carotid and the left subclavian artery to the distance between the innominate and the left common carotid artery. Large distance between the left common carotid and the left subclavian artery was reflected by high value of the derived ratio. In neonates with aortic coarctation, the ratio was 1.69, SD +/- 0.66, compared to 1.04, SD +/- 0.40 in the control group. In older children this ratio was less discriminatory. We also observed that the left subclavian artery formed an acute angle (less than 90 degrees) with the proximal (upstream) segment of the aortic arch in infants with aortic coarctation. In all control infants, this angle was equal to or greater than 90 degrees. A corresponding necropsy study confirmed the echocardiographic findings. We conclude that distal displacement of the left subclavian artery is associated with coarctation of the aorta. It can be accurately visualized and objectively assessed by the two-dimensional echocardiographic technique proposed.