Aortic dissection

An aortic dissection is where part of the tunica intima (which is the endothelial, or the innermost layer of a blood vessel) of the aorta is ripped off. What happens is a tear in the tunica intima of the aorta forms, and the high-pressured blood flowing through the aorta begins to tunnel between the tunica intima and the tunica media, separating the two layers. This is widely accepted as an unideal situation.

Now as the high-pressured blood continues to shear more and more of the tunica intima off the tunica media, blood starts to pool between the two layers, increasing the outside diameter of the blood vessel. The area where blood collects between the tunica intima and the media is called a false lumen, and the true lumen is the regular lumen of the blood vessel.

Since high pressure is a cause of aortic dissection, it’s no surprise that the aorta is the prime target for this problem. So what causes aortic dissections? Well, chronic hypertension is the major cause, whether the hypertension is caused by stress or from increased blood plasma volume like in pregnancy. Blood vessel coarctation, which is the narrowing of a blood vessel, also can cause dissection.

Aortic dissections most often happen in the first 10 cm of the the aorta closest to the heart. In order for an aortic dissection to occur, an underlying condition usually has to exist that weakens the aorta’s wall. Connective tissue disorders like Marfan’s and Ehlers-Danlos syndrome can cause a dissection, as well as a decreased blood flow to the vasa vasorum. Aneurysms can be a cause of aortic dissection as well, and incidentally dissection can also cause aneurysms because again, the dissection weakens the blood vessel wall.