Right circumflex aorta

Case contributed by Dr Mona Mohamed Naguib Sabala

Presentation

Known case of learning difficulties. Presenting with cough on swallowing ? possible aspiration.

Patient Data

Age: 45 years
Gender: Male
Fluoroscopy

Water-soluble contrast swallow was initially done to rule out aspiration.

Unfortunately, the exam was limited as the patient is known to have learning difficulties. However, it showed prominent posterior indentation of the thoracic esophagus & CT was advised for further assessment. No aspiration noticed during the exam. 

CT

 CT angiogram revealed a right-sided aortic arch crossing the midline posterior to the esophagus, further descending on the left side (circumflex aorta). The circumflex arch is ectatic and measures 38 mm in its maximum diameter. Marked compression on the posterior aspect of the esophagus by the ectatic circumflex arch is also noted.

The first branch arising from the arch is the left common carotid artery, followed by the right common carotid artery, right subclavian artery, and finally the aberrant left subclavian artery which arises from a small diverticulum after the aortic arch has crossed the midline to the left. A left ductus arteriosus is also present which completes the vascular ring. The thoracic aorta descends on the left side. The diagnosis is consistent with right circumflex aorta with aberrant left subclavian artery. 

These are annotated images to show the circumflex retroesophageal right aortic arch and its branching pattern. 

Case Discussion

Right circumflex aorta, also referred to as circumflex retroesophageal right aortic arch, is an extremely rare vascular anomaly. It accounts for less than 0.1 % of the vascular rings which themselves encompass only 1-3 % of all congenital heart disease. It is caused by a right aortic arch with a left ductus/ligamentum arteriosum and left descending aorta. 

Embryologically, it develops when there is regression of the left fourth branchial arch and persistence of the left ductus arteriosus and left dorsal aorta. However, it has also been postulated that the higher proximal aortic arch in this anomaly may arise from the third primitive aortic arch, whereas the distal arch may arise from the fourth arch, which could account  for both the higher position of the proximal arch and the elongated length of the transverse aortic arch.

In this anomaly, the right aortic arch itself crosses the midline posterior to the esophagus and trachea (usually at the level of T4 or T5 vertebra). After crossing the midline, the aorta gives rise to a left diverticulum from which the left ductus arteriosus/ligamentum areriosum arises and completes the vascular ring. Even in the absence of a ligamentum arteriosum, the circumflex aorta it self, especially if ectatic, can cause symptomatic tracheal and/or esophageal compression. There are two possible branching patterns, which depend on whether the left subclavian artery is aberrant or not. The first arch vessel maybe the left brachiocephalic, followed by the right carotid and then the right subclavian artery, or the left carotid artery alone arises as the first branch, followed by the right carotid, right subclavian, and the aberrant left subclavian artery (which arises from an aortic diverticulum after the aorta has crossed the midline). The latter branching pattern is more common and is the one in the above case.The descending thoracic aorta descends on the left, as aforementioned.

CT angiography (CTA) is the imaging modality of choice for diagnosis, it is a noninvasive technique that enables rapid and detailed evaluation of the vascular anomalies, in addition to assessment of tracheal or esophageal compression, if present, in the same study. Circumflex retroesophageal right aortic arch can mimic an aneurysm on CT angiograph; however, identification of this anomaly is important, as it is usually symptomatic and patients with severe symptoms may require an aortic uncrossing procedure, in which the distal aortic arch is transected and the retroesophageal segment mobilized anterior to the trachea, followed by its anastomosis with the ascending aorta.

 

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