Aortic intramural hematoma: aspects of pathogenesis 2011.

Non-invasive tomographic imaging modalities have recently contributed to identifying aortic intramural hematoma, a variant form of classic dissection, which is characterized by the absence of an intimal tear and thus the absence of direct flow communication, and which represents an important disease entity in acute aortic syndrome. Clinical investigations have revealed that intramural hematoma has characteristic clinical features and that the natural remodeling process of hematoma is different from that of classic aortic dissection. These findings suggest that intramural hematoma is not just a precursor to aortic dissection, but may be a unique disease entity with a more favorable prognosis compared to aortic dissection. There is regional heterogeneity regarding the relative incidence of this hematoma, with higher incidence seen in Eastern countries. Due to favorable outcomes with medical treatment in Asian patients with type A intramural hematoma, a tailored or individualized approach based on risk stratification using initial clinical information and including imaging studies and timely surgical repair has been suggested in hemodynamically stable patients; however, these results need to be confirmed in other patient populations. The concept of a "micro-tear" which cannot be easily visualized using conventional imaging modalities has been raised: "echo-free space" on transesophageal echocardiography and "focal contrast enhancement" on ultra-fast computerized tomography have drawn many physicians' attention, and the possibility of a pathophysiologic link between classic aortic dissection and intramural hematoma has been discussed. Further investigations are needed to test whether intramural hematoma begins with an initial intimal tear and a different aortic status--characterized by a more rigid and non-compliant aorta associated with old age or long-standing hypertension--and results in an apparently absent intimal flap.