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Key Concepts

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  • Epidemiology

    • Aortic dissection is the most common fatal disease process of the aorta. Increasing awareness of the clinical impact of the condition is reflected by the coining of the term “acute aortic syndrome” (AAS), meant to stand in contrast to the far more common but less lethal “acute coronary syndrome” (ACS). AAS refers to the related processes of acute dissection (AD), intramural hematoma (IMH), and penetrating aortic ulcer (PAU). Although all studies are subject to ascertainment bias as some number of patients surely go undiagnosed, the best estimates of the incidence of aortic dissection derive from a handful of population-based analyses. Estimates from such studies put the incidence somewhere between 2 and 7/100,000. AD is roughly twice as common among men than women, and typically presenting among men in their late 40s to early 60s while women more often present in their 70s. IMH and PAU tend to occur in older patients, and more often affect the descending than the ascending thoracic aorta. AAS occur more frequently in the winter months than summer months, and more often in the morning than evening.

  • Pathophysiology

    • AD is a mechanical failure of the aortic wall, and is associated with deterioration of the material properties of that structure. Histologically, this is reflected by medial degeneration—classically referred to as “cystic medial necrosis”—characterized by smooth muscle cell loss and elastin fragmentation. These changes may occur in the setting of some genetic disorders such as Marfan syndrome, Ehlers–Danlos syndrome, and other familial thoracic aortic syndromes, but are also normal consequences of aging. Factors that accelerate this process include hypertension and tobacco abuse, predisposing patients to aortic catastrophe. The inciting event is commonly held to be an intimal tear that permits entry of blood into the weakened media with distal and, in some cases, proximal propagation. In contrast, IMH is thought secondary to primary rupture of intramural vasa vasora. IMH can progress to AD, and some thinkers argue that all AD in fact begin as IMH. PAU may lead to IMH or AD.

  • Clinical features

    • Although AD can be painless, most often it is associated with the acute onset of severe, tearing, migratory pain. These symptoms may be associated with unequal extremity blood pressures as well as a changing pulse exam (as the dissection evolves), either hypertension or hypotension, and/or a new murmur of aortic regurgitation. Although the presentation can be dramatic, with associated end-organ complications, such as syncope, cerebrovascular accident, anuria, or ischemic bowel, equally once the acute pain has passed the diagnosis may be subtle. Misdiagnosis of AD as ACS or other conditions such as pulmonary embolus is the rule not the exception. Accordingly, a high index of suspicion and low threshold to perform appropriate imaging studies are critical. The mortality rate associated with AD untreated is estimated at 1 to 2 percent per hour during the first 24 to 48 h and 75 percent at 2 weeks.

  • Diagnostics

    • The diagnosis of dissection is critically dependent upon ...

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