Aortic dissection occurs when an injury to the innermost layer of the aorta allows blood to flow between the layers of the aortic wall, forcing the layers apart. In most cases this is associated with a sudden onset of severe chest or back pain, often described as “tearing” in character. Also, vomiting, sweating, and lightheadedness may occur. Other symptoms may result from decreased blood supply to other organs such as stroke or mesenteric ischemia. Aortic dissection can quickly lead to death from not enough blood flow to the heart or rupture of the aorta.
Source: Aortic Dissection wikipedia