Aortic Arch Aneurysm

An isolated aortic arch aneurysm is an uncommon disease entity and often remains clinically silent, given its indolent growth pattern. Aneurysms of the aortic arch are commonly found in association with aneurysms of the adjacent ascending or descending aorta. The true incidence and natural course are still relatively unknown; however, aneurysms involving the arch pose a significant challenge pertaining to surgical management and can be complicated by neurological injury and life-threatening cardiovascular events. Definition A true aneurysm is defined as a pathological dilation of a segment of a blood vessel involving all three layers of the vessel wall (tunica intima, media, and adventitia) and having at least a 50% increase in diameter compared with the expected normal diameter of the artery. Aortic arch aneurysms include any thoracic aneurysm that involves the brachiocephalic vessels. Anatomy The aortic arch is derived from the left branch of the fourth pharyngeal arch during embryonic development. It represents the continuation of the ascending thoracic aorta, which begins at the level of the upper border of the second sternocostal joint of the right side; courses posteriorly, superiorly, and to the left. The distal portion of the aortic arch lies to the left of the trachea, transverses downwards, and terminates adjacent to the lower border of T4, where it continues as the descending aorta.The upward convexity of the aortic arch stems out the following three main branches: Brachiocephalic trunk (innominate artery): It further divides into the right subclavian and right common carotid arteries and supplies blood to the right arm and right head and neck. Left common carotid artery: It carries blood to the left side of the head and neck. Left subclavian artery: It is the most distal branch and distributes blood to the left arm.