Chapter30 Aorta

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Chapter 30: Thoracic Aorta

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Figure 30.14.  Right Arch and Mirror-Image Branching. A : Axial CTA images in a patient with repaired tetralogy of Fallot demonstrate a right aortic arch ( * ). B : A 20-mm coronal MIP image shows the right arch (*). The first branch off the right arch is the left brachiocephalic artery ( black arrow ), which divides into the left subclavian ( white arrow ) and left com- mon carotid ( yellow arrow ) arteries. The next branch off the arch is the right common carotid artery ( black arrowhead ) and the last branch is the right subclavian artery ( red arrows ). C : Axial image above the arch shows the left subclavian ( white arrow ), left common carotid ( yellow arrow ), right common carotid ( black arrowhead ), and right subclavian ( red arrow ) arteries. There is no retroaortic subclavian artery.

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to the esophagus, often with an associated diverticulum of Kommerell (Fig. 30.13). This is most commonly associated with left-sided ligamentum arteriosum which forms a vascular ring that can cause symptoms due to compression. However, the ligamentum itself is usually not visualized on imaging. In right aortic arch with mirror-image branching, the first branch is the left brachiocephalic artery which divides into the left common carotid and subclavian arteries, followed by the right common carotid artery and right subclavian artery (Fig. 30.14). If an aberrant subclavian artery is present, there cannot be mirror-image branching. Congenital heart disease, especially tetralogy of Fallot, is commonly seen with right arch and mirror-image branching. Right aortic arch with iso- lated arch vessels is extremely rare and associated with con- genital heart disease. Isolation indicates that the vessel arises from the pulmonary artery rather than the aorta.

Double Aortic Arch

Right aortic arch with aberrant left subclavian artery and dou- ble aortic arch represent the two most common vascular rings. Double aortic arch results from persistence of both right and left embryologic aortic arches. The common carotid and sub- clavian arteries arise from their ipsilateral arch, resulting in a four-vessel branching pattern. On frontal projection radiogra- phy, double aortic arch will present as bilateral indentations on the lower trachea (Fig. 30.15). Posterior indentation of the esophagus may be seen on esophagram, similar to that seen in cases of aberrant subclavian arteries (Fig. 30.16). On axial CT or MR images, there is symmetric, four-vessel branching at the thoracic inlet in contrast to right or left arch variants, which results in asymmetric vessel branching.