Two different anatomic systems, the DeBakey and Stanford (Daily) systems, have been used to classify aortic dissection [1,2]. The Stanford system, which is more widely used, classifies dissections that involve the ascending aorta as type A, regardless of the site of the primary intimal tear, and all other dissections as type B. In contrast, the DeBakey system is based upon the site of origin with type 1 originating in the ascending aorta and propagating to at least the aortic arch, type 2 originating in and confined to the ascending aorta, and type 3 originating in the descending aorta and extending distally or proximally.
Aortic intramural hematoma (IMH) is one of the variants of aortic dissection and is classified the same way as classic aortic dissection. It is characterized by the absence of a detectable intimal tear (although microtears may be present) and therefore the absence of continuous flow communication (figure 1).
The false channel usually originates from rupture of the vaso vasorum into the media of the aortic wall (picture 1) . Two mechanisms have been described: spontaneous rupture or rupture induced by a penetrating atherosclerotic ulcer . As described below, the presence of a penetrating atherosclerotic ulcer on noninvasive imaging appears to have prognostic importance, being associated with a higher likelihood of progressive disease with medical therapy . (See 'Penetrating atherosclerotic ulcer' below.)
Aortic IMH is considered a precursor to classic aortic dissection . In different series, aortic IMH accounted for 5 to 20 percent of patients with symptoms consistent with an aortic dissection (eg, acute aortic syndrome) [5-9].
The clinical features, management, and prognosis of IMH will be reviewed here. Similar issues for typical aortic dissections are discussed separately. (See "Clinical manifestations and diagnosis of aortic dissection" and "Management of aortic dissection".)