Association of aberrant subclavian arteries with aortic pathology and proposed classification system.

Objective: Aberrant subclavian artery (aSCA) is a rare anatomic variant whose association with other aortic branch variations and aortic pathology has yet to be established. Knowledge of such an association could be relevant to recommendations for screening and awareness as associated variations are important for operative planning. We describe the incidence of aSCA variations, its association with aortic pathology, and a proposed classification system.

Methods: The thoracic cross-sectional imaging database at Keck Hospital of the University of Southern California from 2006 to 2018 was queried for presence of aSCA. Studies were evaluated for aSCA laterality, variant anatomy, and aortic and branch vessel disease. Medical records were reviewed for associated symptoms and diagnoses. The primary outcome was association of aSCA with aortic pathology (aneurysm or dissection). Secondary outcomes were comparison of right and left aSCA, comparison between the sexes, and creation of a proposed classification system.

Results: Of 98,580 axial imaging studies, 810 studies (0.82%) were identified with aSCA in 312 unique patients. Right aSCA made up the majority of cases (90.1%). All aSCAs had a retroesophageal course. Kommerell's diverticulum (KD) was present in 184 (59%) with an average diameter of 1.67 cm (range, 1.2-3.3 cm). KD was more frequent (84% vs 56%; P = .0003) and larger (2.05 cm vs 1.61 cm; P < .0001) in left aSCA patients. When present, KD was more often symptomatic in left aSCA compared with right aSCA (77.4% vs 49.1%; P = .005). Dysphagia, chest pain, reflux, and asthma were all more common in left aSCA patients. KD was also more common in men (73.3% vs 50%; P < .0001) and larger in men (1.81 cm vs 1.54 cm; P < .0001) but with no difference in symptoms between sexes. Our proposed classification system based on aortic arch branching is as follows: type 1, left arch with right aSCA (59.9%); type 2, left arch with common carotid trunk and right aSCA (30.1%); type 3, right arch with left aSCA (9.6%); and type 4, right arch with common carotid trunk and left aSCA (0.3%). Subtypes describe the right vertebral artery (RVA) and left vertebral artery (LVA) origin: subclavian (s, RVA 90.1%, LVA 96.8%), carotid (c, RVA 9.6%, LVA 0.3%), or arch (a, RVA 0.3%, LVA 2.9%). Overall, 9.9% (31/312) had associated aortic pathology, although the study was underpowered to detect a difference between right aSCA and left aSCA (9.3% vs 16.1%; P = .213). Type 3 and type 4 arches more often have associated aortic pathology, KD, and symptoms.

Conclusions: aSCAs are frequently symptomatic and commonly associated with aortic dissection and aneurysm. Our proposed classification scheme depicts all four aSCA arch variants and accounts for vertebral artery origin variation. These variants are common, and vertebral anatomy can differ greatly. Knowledge of these anatomic variations is critical to planning for endovascular and open repair of aortic arch pathology.