This is a view of the intimal surface of the aorta. Note the long diagonal tear, on the left side of the screen, into which the probe has been inserted. Most cases of aortic dissections are associated with a tear in the intima of the vessel through which blood penetrates the wall of the vessel with propogation along the media. In fact, the term aneurysm is incorrect as there is not a dilatation of the vessel. Dissections are of three types: 1) the ascending aorta and a variable length beyond are involved , 2) only the ascending aorta is involved, and 3) either the descending aorta alone or the descending plus a variable length beyond is involved. Types 1 and 2 are sometimes classed together as Type A dissections and Type 3 as Type B dissections . Ninety percent of the dissections occur in the ascending aorta. Aortic dissection has a fifteen minute mortality rate of thirty-five percent if untreated. Some dissections can become chronic or may even heal spontaneously. Common etiologies for dissection are HTN, cystic medial necrosis as with Marfan's syndrome, jet lesions from valve defects, medial necrosis from thrombosis of the vasa vasorum, and other connective tissue disorders affecting the media of the aorta.
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