Aortic Aneurysm Aneurysm of Aorta or Major Branches An aneurysm of the aorta or major branches is an abnormal dilation or bulging in the wall of the aorta or its major branches due to weakened vessel walls. According to the SSA definition, these aneurysms can lead to life-threatening complications such as rupture, requiring surgical intervention or ongoing management to prevent catastrophic outcomes.