What is the definition of an aortic dissection?

• A. Tear in at least two layers of the wall of the aorta, with blood coursing between layers
• B. Rupture of the aorta into the peritoneal cavity
• C. Aortic aneurysm rupture into the chest
• D. Thrombus formation in the aorta

Answer: (A)

Aortic dissection happens when blood breaches the inner lining of the aorta and tracks within the wall, splitting the layers apart. An intimal tear allows blood to enter the media, creating a false lumen and separating at least two layers of the vessel wall. That description directly matches a tear through the wall with blood coursing between layers.

This is different from a rupture into the peritoneal cavity or chest, which are full-thickness failures of the vessel with bleeding outside the wall, or from thrombus formation in the lumen, which is clotting inside the vessel rather than separation of wall layers.