Pulmonary artery aneurysm, 3D coloured computed tomography (CT) scan. The heart is at lower left in this view, with the aorta (the body's main blood vessel) arching over the top and down towards lower centre. An aneurysm is a weakening of the walls of a blood vessel, leading to swelling and rupture. Here, the aneurysm is in the trunk of the pulmonary artery. A rupture here would be swiftly fatal. If the condition is detected before rupture, surgery is needed to repair the artery and implant a stent to strengthen its walls. This condition has developed frmo a coronary artery-pulmonary artery fistula. The lung blood vessels are also shown here.