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Computed Tomography of Aortic Arch Anatomy in Adults : Common and Unusual Variants

EK Fishman, MD

Johns Hopkins Hospital
The Russell H. Morgan Department of Radiology and Radiological Science

Simplified Late Stage Aortic Arch Development

Model based on Edwards’ hypothetical double arch with bilateral ducti.

Breaks at 1 and 2 lead to left arch
Breaks at 3 and 4 lead to right arch.

Break at 1, with resorption of the right ductus, results in normal anatomy.
Break at 2 results in left arch with aberrant subclavian; typically the right ductus resorbs.

Break at 4 results in right arch with mirror-image branching; the ductus runs from the innominate artery to the left pulmonary artery, and there is no ring.
Break at 3 leads to right arch with aberrant subclavian; typically the left ductus persists, coursing from the descending aortic diverticulum to the left pulmonary artery, forming a common type of vascular ring.
Break at 5 differs only in that the aberrant vessel is the innominate artery

Normal Anatomy

Predominant human anatomy is a left aortic arch with three great vessels; first, the brachiocephalic trunk, then the left common carotid artery and finally the subclavian artery. This pattern occurs in 65-80% of the cases.
A common brachiocephalic trunk, so-called “bovine trunk”, in which both common carotid arteries and the right subclavian artery arise from a single trunk off the arch, occurs in 10 to 22% of individuals and accounts for more than two thirds of all arch vessel anomalies.

Vascular Ring Hierarchy

If abnormal combination of derivatives of the aortic arch system results in encirclement of the trachea and the esophagus it is often referred to as “vascular ring”.
International Congenital Heart Surgery Nomenclature And Database Committee Classification:
- Double aortic arch
  - Right arch dominant
  - Left arch dominant
  - Balanced arches
- Right aortic arch–left ligamentum
  - Mirror-image branching
  - Retroesophageal left subclavian artery
  - Circumflex aorta
- Pulmonary artery sling

Left AA with aberrant right subclavian artery

The right subclavian artery is the last branch of the aortic arch in l% of individuals.
It courses to the right behind the esophagus in 80% of these cases, between the esophagus and trachea in 15%, and anterior to the trachea or mainstem bronchus in 5%.
A retroesophageal course may be the cause of so-called dysphagia lusoria.
Another variant - aberrant right brachiocephalic artery is rare

Abberrant Right Subclavian Artery

Right AA with aberrant left subclavian artery

Right aortic arch is an uncommon anatomical anomaly that occurs in <0.1% of the population.
The most common type is the right aortic arch with an aberrant left subclavian artery
The vessels originate in the following order: left common carotid, right common carotid, right subclavian, and left subclavian artery.
Symptoms may arise from vascular ring formation as congenital heart disease is rare in this variant.

Right AA with mirror image branching

The mirror-image type of the right aortic arch (left brachiocephalic trunk, right common carotid and subclavian arteries) is almost always associated with congenital heart disease, especially the cyanotic type.

Double aortic arch

Rare anomaly caused by persistence (to varying degree) of the fetal double aortic arch system.
The ascending aorta divides into two arches that pass to either side of the esophagus and trachea and reunite to form the descending aorta.
Form of complete vascular ring, resulting in noncardiac morbidity, but rarely associated with intracardiac defects.
The descending aorta is usually on the left side.
Most commonly, one arch is dominant, whereas the other may be of small caliber or represented by a fibrous band

Hybrid lesion – CPAM type I and intralobar sequestration

Hybrid lesion is a term that reflects that a lesion has features of both CPAM and bronchopulmonary sequestration
Congenital lung abnormalities lie on a spectrum of abnormal parenchymal and vascular abnormalities
In hybrid lesions, identifying the feeding artery can help determine that the lesion demonstrates features of bronchopulmonary sequestration
CR can demonstrate these feeding vessels, as well as demonstrate the associated pulmonary parenchymal abnormalities

The coronal CR images demonstrate the double aortic arch, with a dominant right sided arch, which is the typical configuration. Both common carotid arteries and the left subclavian artery are well demonstrated, however the right subclavian artery is obscured by the overlapping clavicle. The lower CR image also highlights the pulmonary parenchyma and airways, and shows the trachea located posteriorly.

Normal Anatomy

The complete vascular ring is demonstrated on both the standard MDCT image as well as the volume shape and me rendered image below. However the cinematic rendering provides even further anatomic detail of the vascular ring, and shows it completely encircling the endotracheal tube. The adjacent pulmonary vasculature and osseous structures are also well demonstrated.

Normal Anatomy

The coronal CR image highlights the double arch encircling the trachea posteriorly, as they are able to be isolated given the removal of the anterior aspects of the arch. The larger right arch is also nicely shown. The patient underwent surgical repair, with diversion of the non dominant left arch, division of the PDA ligament and aortopexy of the Kommerel diverticulum.

References

Kau T et al. Aortic Development and Anomalies. Semin Intervent Radiol 2007;24:141–152
Hernanz-Schulman M.Vascular rings - a practical approach to imaging diagnosis. Pediatr Radiol 2005; 35: 961–979
Alsaif HA and Ramadan WS. An Anatomical Study of the Aortic Arch Variations. JKAU: Med. Sci., Vol. 17 No. 2, pp: 37-54
Backer CL, and Mavroudis C. Congenital Heart Surgery Nomenclature and Database Project: Vascular Rings, Tracheal Stenosis, Pectus Excavatum. Ann Thorac Surg 2000; 69:S308–18