Aortic arch

Last revised by Jeremy Jones on 28 Jul 2023

The aortic arch represents the direct continuation of the ascending aorta and represents a key area for a review of normal variant anatomy and a wide range of pathological processes that range from congenital anomalies to traumatic injury.

The aortic arch represents the continuation of the ascending aorta. It is nominally defined as starting at the level of the transthoracic plane of Ludwig, a horizontal plane from the sternomanubrial angle to the T4 vertebral body. The sternomanubrial joint is the same level as the second sternocostal articulation.

It courses in a narrow arch from ventral to dorsal and from right to left such that at the end of the arch it sits to the left of midline, adjacent to the thoracic vertebral column. Its peak is at the T3/4 level.

Three main branches originate from the upward convexity of the arch in the majority (75%) of patients. In order from proximal to distal the branches are:

  • brachiocephalic trunk or artery (innominate artery) which goes on to divide into the right subclavian and right common carotid arteries

    • the aortic arch can be divided by the brachiocephalic trunk into "proximal" and "distal" portions 3

  • left common carotid artery

  • left subclavian artery

    • just beyond the last branch, the aortic isthmus represents a minor narrowing at the site of the ligamentum arteriosum, which runs between the undersurface of the aortic arch and the terminal pulmonary trunk, this ligament represents the obliterated foetal ductus arteriosus and due to this attachment, this represents the site of the majority of thoracic aortic injuries when the body undergoes significant deceleration

The arch terminates at the lower border of T4 where it continues as the descending aorta, in the plane of Ludwig, a horizontal plane from the sternomanubrial angle to the T4 vertebral body.

The arch position may be altered:

One of three common variations of the branching pattern can be identified:

  • normal: seen in 75% of patients

  • bovine arch: a common origin of brachiocephalic and left common carotid artery - seen in approximately 15% of patients (more common in individuals of African descent)

  • left common carotid has its origin from the brachiocephalic artery proper, rather than from a common trunk - seen in approximately 10% of patients (also more common in individuals of African descent)

Additional branches may arise directly from the arch:

  • thyroidea ima artery, usually between the brachiocephalic and left common carotid

  • left vertebral artery, usually between the left common carotid and the left subclavian arteries

  • rarely the right subclavian and right common carotid arise independently

See: variant anatomy of the aortic arch.

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