Anatomical variation of the branching patterns of the aortic arch: a literature review

Many anatomical variations of the branching pattern of the aortic arch have been documented within the literature. These variations find their origin in alterations of the embryological development of the arch and thus can be used as antenatal biomarkers for various syndromes. There exist five main branching patterns of the arch of the aorta: the normal configuration; the Bovine Arch (types 1 and 2); the Left Vertebral Artery arising from the arch; Aberrant Right Subclavian Artery; and the Thyroid ima artery. The aim of this study was to analyse the literature to identify the different reported anatomical variations in the branching patterns of the arch and to determine their prevalence. Literature searches of databases EMBASE and MEDLINE were performed in June 2021 and identified 1197 articles, of which 24 articles were considered eligible for inclusion. Twenty-eight variations were found. The prevalence of the normal branching configuration ranged from 61.2% to 92.59%; prevalence of the bovine arch type 1 ranged from 4.95% to 31.2%; while prevalence of the bovine arch type 2 ranged from 0.04% to 24%. Alongside bovine arch types 1 and 2, five concomitant variations found. The left vertebral artery arose from the aortic arch in five different locations. Prevalence of the origin of the left vertebral artery from the arch ranged from 0.17% to 15.3%. Three different combinations existed with the aberrant right subclavian artery. Within the studies examined, the prevalence of this variant ranged from 0.08% to 3.33%. The origin of the thyroid ima from the aortic arch ranged from 0.08% to 2%. Other variations which could not be classified into these six main groups were also found among the literature. These variations have clinical implications for stroke medicine, carotid surgery, radiological investigations, and various surgical specialities such as cardiothoracic, neck and thyroid surgery. They can also result in clinical symptoms such as dysphagia and dyspnoea in the case of aberrant right subclavian artery. Anatomists and clinicians alike should be aware of these variations when planning any radiological, percutaneous or surgical procedure. No ethical approval was required due to the review nature of this research.