Type B acute aortic dissection (AAD) and intramural hematoma (IMH) can both present as potentially catastrophic lesions of the descending aorta. IMH is distinguished from AAD by the absence of an intimal tear and flap. With short-term outcomes being similar to type B AAD, IMH is treated identically to AAD in the corresponding segment of the aorta. While all patients with any acute aortic syndrome of the descending aorta receive prompt anti-impulse therapy, thoracic endovascular aortic repair (TEVAR) is reserved for patients presenting with certain complications, namely malperfusion, rupture, or periaortic hematoma. Technical aspects of TEVAR for IMH include maximal endograft oversizing of 10% with 20 mm landing zones of the healthy aorta, revascularization of the left subclavian artery when covered, use of cerebrospinal fluid drainage with extensive coverage, and restoration of branch vessel perfusion. With respect to disease evolution, IMH may progress to classic AD, frank rupture, or aneurysmal dilation; yet, IMH may also regress and be completely resorbed. However, since the natural history of IMH is unpredictable, TEVAR is being used more aggressively to improve long-term survival, rates of secondary reintervention, and positive aortic remodeling. Much remains unknown for acute type B IMH, including the use of prophylactic TEVAR for stable uncomplicated presentations, as well as the optimal timing of intervention and certain technical aspects of TEVAR. As such, IMH remains a diagnostic and therapeutic challenge for cardiovascular surgeons.
Keywords: acute aortic dissection; aorta; aortic aneurysm; intramural hematoma; type B aortic dissection.
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