Double aortic arch

A 29-year-old man was brought to the emergency department after a car accident. He was previously healthy and asymptomatic.

Chest radiograph performed in the emergency room shows a mediastinal abnormality.
CT is also performed in the emergency setting, which shows, besides the findings resulting from trauma, a double aortic arch, in this case an incidental finding. The ascending aorta is seen to divide into right and left arches. The right arch is higher, larger and more posterior than the left. Each arch gives rise to a subclavian and carotid artery, and no brachiocephalic artery is present giving a symmetric configuration to the great vessels in the supra-aortic mediastinum.

Congenital anomalies of the aortic arch are rare, with its frequency varying between 0.5 to 3.0%. [1] They result from abnormal or incomplete regression of embryonic branchial arches. According to Edward´s hypothesis, there are two aortic arches and two ductus arteriosus in the embryonic period, and the normal anatomy results from the regression of the dorsal segment of the right arch. Interruption of this system in different locations explains the various aortic arch anomalies. [1, 2, 3]
Congenital anomalies of the aortic arch are in most cases incidental findings in asymptomatic patients. However, symptoms may present when a vascular ring occurs and compresses the trachea or oesophagus. Congenital anomalies of the aortic arch may also be associated with congenital heart disease. [1, 2]
CT angiography was considered the best imaging method for characterization of isolated thoracic aortic anomalies, with MRI being an alternative.
A double aortic arch is present in 0.05-0.3% of the population. [1]
In double aortic arch, the ascending aorta divides into two arches. The right arch is usually larger, extends more cephalad and is more posterior than the left arch. The left arch has a course similar to that of the normal left aortic arch, and the right arch has a course behind the oesophagus and joins the left arch. The descending aorta is usually on the left side. The subclavian and carotid arteries arise from their respective arches. [2]
Double aortic arch is the most common cause of complete vascular ring, with the majority of patients presenting with symptoms resulting from compression of adjacent structures in the first months of life (stridor, recurrent respiratory infections or dysphagia). [2, 3] Occasionally, it is an incidental finding in asymptomatic adults. [2]