Classification Anomalies can be classified into four groups, depending on the position of the aortic arch relative to the trachea and the pattern of branching of the brachiocephalic arteries: ■ Left aortic arch with aberrant right subclavian or brachiocephalic artery ■ Right aortic arch with aberrant left subclavian or brachiocephalic artery ■ Right aortic arch with mirror-image branching ■ Double aortic arch Most of the major anomalies produce a complete or partial vascular ring around the trachea and esophagus The only exception is the classic form of right aortic arch with mirror-image branching Aberrant origin of a subclavian or brachiocephalic branch of the aortic arch produces encirclement of the trachea and esophagus because the anomalous artery takes a retroesophageal course The arterial duct, regardless of whether it is patent or ligamentous, may also contribute to encirclement of the trachea and esophagus Occasionally the distal aortic arch itself has a retroesophageal course that causes esophageal and tracheal compression Therefore the assessment and description of the anomalies should include description of: ■ The position of the aortic arch relative to the trachea ■ The location of the most proximal part of the descending aorta in relation to the spine ■ The presence or absence of an aberrant branch ■ The origin and insertion of the patent or ligamentous arterial duct or, rarely, ducts The anomalies producing a complete or partial vascular ring around the trachea and esophagus are: ■ Aortic arch anomalies forming a complete vascular ring: ■ Double aortic arch ■ Right aortic arch with aberrant left subclavian or brachiocephalic artery and left-sided arterial duct ■ Left aortic arch with aberrant right subclavian or brachiocephalic artery and right-sided arterial duct ■ Right aortic arch with mirror-image branching and retroesophageal left arterial duct between right-sided descending aorta and left pulmonary artery ■ Circumflex retroesophageal aortic arch ■ Aortic arch anomalies forming a partial vascular ring: ■ Left aortic arch with aberrant right subclavian or brachiocephalic artery and left-sided arterial duct ■ Right aortic arch with aberrant left subclavian or brachiocephalic artery and right-sided arterial duct Other anomalies that may have clinical significance include the cervical aortic arch, isolated origin of the left or right subclavian artery from a pulmonary artery, and double-barreled, or double lumen, aortic arch