Subaortic left innominate vein: radiologic findings and consideration of embryogenesis.

To propose a hypothesis about the embryogenesis of the subaortic left innominate vein, the authors reviewed the radiologic features of 14 patients diagnosed with subaortic left innominate vein made by computed tomography or magnetic resonance imaging scan. The authors retrospectively analyzed the level of the aortic arch, associated aortic arch anomalies, and the presence or absence of obliteration of the prevascular space. A high aortic arch was seen in 10 patients, five with a cervical, two with a right and, one with a double aortic arch. The prevascular space was occupied by the aortic arch, the great arteries, or both in all 10 patients with a high arch. In the remaining four patients with a normal aortic arch, the prevascular space was preserved, but abnormal elongation of the aortic segment between the left common carotid artery and the left subclavian artery was seen in three. The authors postulate that precardinal anastomosis can develop in any pathway where there is the available space. In the presence of abnormal elongation of the aortic arch and resultant widening of the subaortic space, the chance of the development of a subaortic left innominate vein increases.