An aortic aneurysm is a stretched and bulging area in the wall of the aorta. The aorta is the large artery that carries oxygen-rich blood from the heart to the rest of the body. A thoracic aortic aneurysm happens in the section of the aorta that is in the chest.

Thoracic aortic aneurysms are also known as ascending or descending aortic aneurysms.