Right Aortic Arch With Isolation of the Left Innominate Artery Arising From the Pulmonary Artery and Atrial Septal Defect

Abstract

A 6-month-old child (weight, 6.250 kg) was referred for evaluation of a systolic murmur and congestive heart failure. Echocardiography revealed right-sided cardiac chamber enlargement and an atrial septal defect, with right aortic arch and no clear visualization of the left pulmonary artery take-off. Angiography confirmed the diagnosis of right aortic arch, with the right carotid artery being the first branch and perfusing through the vertebrobasilar circulation the left carotid and subclavian vessels in a retrograde fashion. The former emptied through a left innominate artery into the pulmonary vessels, displaying a left-to-right shunt. In addition, the left subclavian artery was fed from a plexus of collaterals coming from the upper intercostal branches (Fig 1; A = aorta; AA = ascending aorta; IA = innominate artery; LBP = left branch-pulmonary; LCC = left common carotid; LDA = left descending coronary aorta; LSC = left subclavian; P = pulmonary artery; RDA = right descending coronary aorta; RPB = right pulmonary branch; RSC = right subclavian). On cardiopulmonary bypass, the atrial septal defect was closed. Then the ductus was transected, the pulmonary stump was oversewn, and the free end was reimplanted end-to-side to the ascending aorta, thus creating a mirror-like arrangement of the branches (Fig 2; LCC = left common carotid; LPA = left pulmonary artery; LS = left subclavian; RCC = right common carotid; RS = right subclavian). Edwards proposed in 1948 that all abnormalities of the aortic arch could be explained by a model involving a double aortic arch with right and left ductus, followed by resorption and remodeling of particular segments. In the case of our patient, the regression of the portion proximal to the left common carotid (so-called D) and the segment distal to the left subclavian (so-called A), plus the patency of the left ductus, gave rise to the arrangement of an isolated left innominate artery in the setting of a right-sided aorta (Fig 1). Because our patient presented an atrial septal defect, surgery was scheduled through a mid-sternotomy and under extracorporeal circulation. On reimplanting the left innominate artery in the ascending aorta, a physiological setting was achieved (ie, a right aortic arch with mirror-image arrangement of the neck vessels, plus interruption of the left-to-right shunt).