Aortic dissection is a potentially life-threatening condition in which there is bleeding into and along the wall of the aorta, the major artery leaving the heart.

Aortic dissection most often occurs because of a tear or damage to the inner wall of the aorta. This usually occurs in the thoracic (chest) portion of the artery, but may also occur in the abdominal portion.

The aorta has different branches through which blood flows. An aortic dissection is classified as type A or B depending on where it begins and ends.

• Type A begins in the first (ascending) part of the aorta and typically moves to another part of the chest.
• Type B begins in the last (descending) part of the aorta and moves down the abdomen.

When a tear occurs, it creates two channels: One in which blood continues to travel and another where blood remains still. As the aortic dissection grows bigger, the channel with nontraveling blood can get bigger and push on other branches of the aorta.

An aortic dissection may also involve abnormal widening or ballooning of the aorta (aneurysm).

The exact cause is unknown, but risks include atherosclerosis (hardening of the arteries) and high blood pressure. Traumatic injury is a major cause of aortic dissection, especially blunt trauma to the chest as can be caused by hitting the steering wheel of a car during an accident.

Other risk factors and conditions associated with the development of aortic dissection including:

• Bicuspid aortic valve
• Coarctation (narrowing) of the aorta
• Connective tissue disorders
• Ehlers-Danlos syndrome
• Heart surgery or procedures
• Marfan syndrome
• Pregnancy
• Pseudoxanthoma elasticum
• Vascular inflammation due to conditions such as arteritis and syphilis

Aortic dissection occurs in approximately 2 out of every 10,000 people. It can affect anyone, but is most often seen in men aged 40 to 70.