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Acute aortic syndromes (AAS) are constellation of potentially life-threatening pathologies characterized by disruption of tunica media layer of the aortic wall. It includes a spectrum of disease entities consisting of aortic dissection (AD), penetrating aortic ulcers (PAUs), and intramural hematomas (IMH). Age and sex-adjusted incidence of AAS is reported to be 7.7 cases per 100,000 person-years.1,2 In this chapter, we will focus on pathophysiology, epidemiology, natural history, and treatment of PAU and IMH.
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PENETRATING AORTIC ULCER (PAU)
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PAU is a focal disruption in the intima and internal elastic lamina of the aorta typically caused by erosion of an atherosclerotic plaque and corresponding inflammatory changes in the aortic wall. PAUs can present as an isolated entity or concomitantly with IMH and ADs. Similar to ADs, PAUs are classified using the Stanford classification. Type A PAUs occur in the ascending aorta, whereas type B PAUs occur in the descending aorta. PAUs are located in the aortic arch in 7% of cases, descending thoracic aortic in 63% of cases, and abdominal aorta in 30%.3 In patients with symptomatic PAU on presentation, rupture rates of up to 45% have been reported.3
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First described by Shennan in 1934, PAUs are responsible for 2% to 10% of AAS and are disproportionately found in older patients with advanced atherosclerotic disease as opposed to ADs, which are more prevalent in young hypertensive patients.1,4 The incidence of PAU is 2.1 per 100,000 person-years. It most commonly affects older patients with diffuse atherosclerosis and significant cardiovascular risk factors; however, young patients with connective tissue diseases are also at high risk.2
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INTRAMURAL HEMATOMA (IMH)
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IMH, identified by Krukenberg in 1920, is defined as an accumulation of hemorrhage in the tunica media without an identifiable intimal tear on imaging. Classically, IMH was thought to be due to vasa vasorum rupture. However, new theories suggest that a transient intimal tear allowing for accumulation of blood in the media layer of the aortic with subsequent thromboses of blood may be responsible.5 Interestingly, these tears seem to occur in a plane closer to the adventitia than classic dissections which may explain IMH’s propensity for rupture.6 The accumulated hemorrhage can then infarct the aortic wall predisposing the patient to AD, pseudoaneurysm development, and aneurysmal degeneration.1,7–9 While IMH may present with symptoms similar to an AD, they occur in the absence of false lumen flow and are most commonly localized to the descending thoracic aorta in 50% to 85% of cases.5
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The precise prevalence of IMH in AAS remains unclear, with reported rates ranging from the low-single digits to as high as one-third of all AAS cases. The International Registry of Acute Aortic Dissection (IRAD), comprising 30 aortic centers in 10 countries, reported a rate of only 6.3% while several Asian studies report rates of ...