An Aortic Aneurysm is an abnormal enlargement (bulging) of part of the wall of the aorta. It is most commonly a result of atherosclerosis. The aorta begins within the heart. The aorta travels upward, then bends and then travels down beside the spine. The bend is known as the aortic arch. Type A aneurysms are found above the aortic arch and type B aneurysms are found below the aortic arch.