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.