An aortic dissection sometimes referred to as a "dissecting aorta" or "dissecting aneurysm," is the most common catastrophe of the aorta. An aortic dissection begins with a tear in the inner layer of the aortic wall (the intima). The force of the blood entering the middle layer (the media) causes the tear to extend. It typically extends distally (away from the heart) in the direction of blood flow but it may extend proximally (closer to the heart). As a result of the tear, blood is then channeled into the wall of the aorta, rather than into the central lumen, separating the layers of tissues. This creates a "false lumen" and results in decreased oxygen delivery to important organs including the brain, heart, kidneys, and intestines. It also generates a weakening in the aortic wall with a potential for rupture.
An aortic dissection is a life-threatening emergency. As many as 40% of people who experience aortic dissections die instantly, and the risk of death increases 1-3% every hour. Between 75-90% of patients who experience the most common type of dissection (those located in the part of the aorta closest to the heart) die within one week if not treated appropriately. While some types of aortic dissections do not require emergency surgery, most do. Regardless, patients with acute aortic dissections should be emergently referred to a center that specializes in the treatment of aortic diseases.