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Abnormalities seen in the great arteries view

Aberrant Right Subclavian Artery

An aberrant right subclavian artery (ARSA) is a subtle cardiac finding, which can be categorised as anatomical variant rather than true abnormality. It can be isolated or part of intracardiac anomaly

The right subclavian artery usually arises above the level of the aortic arch, as the first branch from the innominate (or brachiocephalic artery), which in turn is the first vessel that arises from the aortic arch. An ARSA arises anomalously as a fourth branch of the aortic arch at the level of the arterial duct. In contrast to the normal vessel, which arises at the level of the shoulders and travels almost horizontally rightwards, the aberrant vessel arises from the first portion of the descending aorta and passes behind the trachea and cranially as well as rightwards. Hence, the course of an ARSA would not be seen in a standard long-axis view of the aortic arch.

Prevalence

ARSA is found in about 1 in 100 live births.

Other abnormalities

ARSA is observed in up to 30% of fetuses with trisomy 21. The likelihood ratio for trisomy 21 with ARSA in the absence of other defects or markers of aneuploidy is about 4. There is also a possible association between ARSA and 22q11.2 deletion.

Prognosis

There are no adverse consequences of ARSA. Rarely, dysphagia caused by compression of the trachea and esophagus may occur.

 A case of ARSA

Colour flow mapping demonstrates the left aortic arch crossing the midline in front of the trachea (arrowhead) and meeting the arterial duct in front of the spine creating a “V” shape appearance (yellow lines). There is forward flow within the aortic arch and pulmonary artery. There is an ARSA arising from the descending aorta (red line), behind the trachea (arrowhead) and below the level of the aortic arch at the level of the duct.