[A case of dissection of the right aortic arch, with consideration on the development of its major branches and ductus arteriosus].

In the present study, we reported a case of the right aortic arch which was found in the course of dissection at Juntendo University in 1993 from a cadaver of a 92-year-old female. The present case possessed as its terminal branch the right subclavian artery. The ascending aorta arose from the left ventricle and ran upwards, curved dorsally and became the right aortic arch. The arch passed on the right side of the trachea and esophagus, curved right posteriorly and became the thoracic aorta which descended on right side of the vertebral column. The aortic arch sent off the left brachiocephalic artery, the right common carotid artery and the right subclavian artery in this order and connected with the pulmonary artery by the right ligamentum arteriosum. The present case represents the 11th report of dissection of a right aortic arch in Japan which was type M according to the classification system of Adachi-Williams-Nakagawa. Type M is subdivided into three subtypes depending on the pattern of the ligamentum arteriosum. The right ligamentum arteriosum has been found in three cases including the present study. We critically discussed previous explanations and theories on the developmental processes of the right aortic arch and its variable major branches and ductus arteriosus.