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Cardiovascular Imaging

Aberrant subclavian artery

anomalous origin from the proximal descending aorta of either the right or left subclavian artery. An aberrant right subclavian artery arises distal to the left aortic arch. An aberrant left subclavian artery arises distal to the right aortic arch (nonmirror-image right aortic arch); an aortic diverticulum exists at the site of origin. In a right arch with aberrant left subclavian artery, a right-sided ligamentum arteriosum connects the diverticulum and the proximal left pulmonary artery producing a complete vascular ring. In both types of aberrant subclavian arteries, the vessel runs behind the oesophagus. The aberrant right subclavian artery produces an impression on the back of the oesophagus while the left one usually causes anterior displacement and severe compression of the oesophagus. The latter also frequently causes airway compression. The right aberrant artery can be associated with dysphagia in adults while the left usually causes symptomatic airway and oesophageal obstruction during infancy or early childhood.

Plain radiography with barium swallow displays a right-sided aortic arch impression and posterior impression of the aberrant left subclavian on the oesophagus or left-sided aortic arch impression and posterior impression of the aberrant left subclavian artery on the oesophagus. The lateral view also reveals anterior displacement and compression of the trachea by the aberrant left subclavian artery. Thoracic aortography demonstrates the relationship of the arch to the trachea or oesophagus (simultaneous barium swallow) and origin of the aberrant subclavian as the fourth major branch of the aortic arch.

Definitive diagnosis is now usually accomplished by CT or MRI. Both display the severity of airway narrowing and the retro-oesophageal aberrant artery (Fig.1). Both demonstrate the large aortic diverticulum invariably at the site of airway compression with an aberrant left subclavian artery.

CBH

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Fig.1

ECG-gated transaxial spin-echo image shows a right aortic arch and the left subclavian artery on the left posterior aspect of the oesophagus.
Aberrant subclavian artery, Fig.1