Variant of the aortic arch
Variant anatomy of the aortic arch occurs when there is failure of normal aortic development. It results in a number of heterogenous anomalies of the aorta and its branch vessels.
Normally, the aorta ascends in the superior mediastinum to the level of the sternal notch before arching posteriorly and descending in the left hemithorax. The arch gives off three branch vessels, the brachiocephalic (also called the innominate), left common carotid and left subclavian arteries.
Aortic development is a complex process that takes place during the third week of gestation. During development, the two dorsal aortae fuse to form the descending aorta, the ventral aortic limbs fuse to form the aortic sac, the left 4th arch vessel becomes the aortic arch and the right 4th arch vessel becomes atretic distally.
Common arch anomalies
Other arch anomalies
- hypoplastic ascending aorta
- coarctation of the aorta
- interrupted aortic arch
- patent ductus arteriosus
- cervical aortic arch
- ductus diverticulum
- circumflex aorta
Branch vessel anomalies
Abnormal formation of the 1st, 2nd and 3rd arch vessels results in abnormal branch vessels:
- bovine arch (commonest, occurring in 10-20% of the population)
- thyroidea ima artery (between 4-10 % of cases)
- variant origin of vertebral arteries (2.5-6% of cases)
- aberrant right subclavian artery (in 0.6% of cases)
- aberrant left subclavian artery (right-sided arch)
- variant aortic branch vessels
- bronchial arteries (case)