Aorta surgery. Artificial blood vessel (white, upper centre) being stitched in place to replace an aneurysm (swelling) of the aortic arch. The aortic arch is the first part of the aorta (the main body artery) where it emerges from the top of the heart. The chest wall has been opened up and blood has been rerouted from this area to allow the surgery to take place. The artificial aortic arch needs to be attached to both the heart and the remainder of the aorta. If an aneurysm is not repaired, it may burst and cause fatal internal bleeding. For images of the surgery, see M551/331- 336.