A person with a dissecting thoracic aneurysm has a swollen and weakened area in the wall of the aorta. The aorta is the largest artery in the body. The aorta begins at the heart and travels to the abdomen.

A thoracic aneurysm is dissecting when the layers of the aortic wall are tearing apart. Over time, the aneurysm can rupture, which can cause death from sudden, severe bleeding into the chest.