-2 :: Case - 4842 ::
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Tx and Followup:
None. This finding is a normal variant. The child is otherwise healthy and is fortunate not to have a right-sided aortic arch with a mirror image branching pattern, which has an extremely high assocation with congenital anomalies.

Additional Discussion:
Please see the accompanying factoid.

Discussion Author: Richard P. Moser, III

There are three main classes of right-sided aortic arch anomalies:
1). RIGHT AORTIC ARCH WITH MIRROR IMAGE BRANCHING
*associated congenital heart disease in 98% of patients (unless situs inversus present)
-->occurs in 35% of patient’s with truncus ateriosus and 30% of patients with Tetralogy of Fallot; however, due to the much greater incidence of Tetralogy, this abnormality is most often seen in association with Tetralogy of Fallot (90%), followed by truncus arteriosus (2.5%), transposition of the great vessels (1.5%), and ASD/VSD (0.5%)
*arch and descending aorta are both on the right side
*arch gives rise to left innominate artery, then right common carotid artery, then right subclavian artery
*caused by interruption of the embryonic left arch just distal to the left ductus arteriosus
*THERE IS NO POSTERIOR IMPRESSION ON THE BARIUM-FILLED ESOPHAGUS.

2). RIGHT AORTIC ARCH WITH AN ABERRANT LEFT SUBCLAVIAN ARTERY
*caused by interruption of the left arch between the left common carotid artery and the left subclavian artery
*the left ligamentum or ductus completes the vascular ring, resulting in compressive symptoms in 5% of patients, usually associated with a large aortic diverticulum at the origin of the left subclavian artery as well as a tight left-sided ligamentum arteriosum
*increased incidence of cardiac defects (5-12%) compared to normals (<1%): Tetralogy of Fallot (71%), ASD/VSD (21%), aortic coarctation (7%)

3). RIGHT AORTIC ARCH WITH ISOLATION OF THE LEFT SUBCLAVIAN ARTERY
*caused by interruption of the left arch at two levels: (1) between the left common carotid artery and the left subclavian artery and (2) just distal to the left ductus arteriosus
*the left subclavian artery arises from the left pulmonary artery via the left ligamentum or ductus arteriosus
*arch and descending aorta are both on the right side
*THERE IS NO POSTERIOR IMPRESSION ON THE BARIUM-FILLED ESOPHAGUS.
*causes a subclavian steal phenomenon via siphoning of blood from the left vertebral artery
-->check for decreased or absent left upper extremity pulse
*most cases occur in patients with Tetralogy of Fallot

Four vascular impressions seen on the barium esophagram include:
1). Posterior impression on esophagus AND anterior impression on trachea-->double aortic arch or right aortic arch with aberrant left subclavian artery.
2). Anterior impression on the trachea-->innominate artery or common carotid artery compression.
3). Posterior impression on the esophagus-->left aortic arch with aberrant right subclavian artery
4). Posterior impression on trachea AND anterior impression on esophagus-->pulmonary sling.

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