Dissection occurs within the layers of the media and may rupture through the adventitia or back through the intima. The false channel may reenter the true aortic lumen at any point. The blood supply of any tributary artery of the aorta may be compromised, and the aortic valve may be rendered incompetent. Death often follows from rupture of the aorta, usually into the pericardial cavity or left pleural space. Dissection may originate anywhere along the aorta, but the most common sites are the proximal ascending aorta within 5 cm of the aortic valve and the descending thoracic aorta just beyond the origin of the left subclavian artery.
Iatrogenic dissection stems from arterial catheterization and cardiovascular surgical procedures.
Another anatomic classification designates dissection involving the ascending aorta as type A and that confined to the descending thoracic aorta as type B. Many physicians simply refer to dissection of the ascending aorta as proximal, and that of the descending aorta as distal. The cardinal symptom is pain, which is present in almost all conscious patients. The pain is typically abrupt in onset and excruciating. It is often described as tearing or ripping. The most common location is the precordium, but pain in the interscapular area is frequent, especially with dissection involving the descending thoracic aorta.