Prosthetic aorta. Coloured angiogram of an artificial aorta (black and red, centre) in place following surgery to repair an aortic aneurysm. The whole thoracic aorta, including the aortic valve in the heart, has been replaced. The heart appears as a rounded pink area occupying most of the lower left of the image. Aortic aneurysms are blood-filled swellings in the wall of the aorta, caused by congenital weakness in the vessel or by accumulation of fatty deposits on its inner surface (atherosclerosis). Rupture of such aneurysms is often fatal, but surgical repair of non-ruptured aortic aneurysms in the chest offers an 80-90% chance of survival.