[1] By separating a portion of the wall of the artery (a layer of the tunica media or in some cases tunica intima), a tear creates two lumens or passages within the vessel, the original or true lumen, and the false lumen created by the new space within the wall of the artery.

Dissections originating in the tunica media are caused by disruption of the vasa vasorum.

It is thought that dysfunction in the vasa vasorum is an underlying cause of dissections.

In the above example, if the aortic dissection extended from proximal to the left subclavian artery takeoff to the mid descending aorta, the common iliac arteries would be perfused from the true lumen distal to the dissection but would be at risk for malperfusion due to occlusion of the true lumen of the aorta by the false lumen.

As a disease family, arterial dissections share common features, including shared genetic risk variants, and commonly perturbed molecular pathways.