A disruption of the wall of the aorta that causes blood to leave the true arterial lumen, either to enter a false lumen between the intima and the deeper layers of the vessel, or to hemorrhage into the chest or abdomen. Aortic dissection usually occurs in patients with aneurysmal dilation of the aorta, but it may sometimes occur as a result of trauma. It often results in sudden death. Some patients may be able to be stabilized with antihypertensive agents, pending attempts at surgical repair.