Anatomical variations in the branches of the human aortic arch: a recent study of a South Australian population.

Variations of the branches of the aortic arch are likely to occur as a result of the altered development of certain branchial arch arteries during the embryonic period of gestation. In the present investigation the pattern of branches of the aortic arch was studied in 81 cadavers from a recent South Australian population of European descent, who have migrated to (n = 38) or were born and lived in (n = 43) South Australia during the twentieth century. Two principal variations were noted in the present study. Firstly, in 6 cadavers, the left vertebral artery originated directly from the arch of the aorta, between the left common carotid and the left subclavian arteries. The 6 subjects were among the subgroup born in South Australia, giving an incidence of 13.95%, which is much higher than in previous reports. The overall incidence of 7.41%, when related to the whole group, is also higher than incidences reported in other populations. The presence of this variation suggests that in some individuals part of the aortic arch is formed from the left 7(th) inter-segmental artery. Secondly, none of the cadavers examined had the thyroidea ima artery, contrasting with previously reported incidences that varied between 4% and 10%. Since all 6 cadavers with the left vertebral artery variant were born in South Australia, it is suggested that environmental factors may have contributed to this variation. Significant environmental changes in South Australia around the turn of the twentieth century are discussed. This study represents the first systematic investigation of the branches of the aortic arch in a South Australian population and provides data relevant to the practice of medicine.