Page 65 - Read Online

Rinaldi et al. Vessel Plus 2024;8:21 https://dx.doi.org/10.20517/2574-1209.2023.65 Page 9 of 19

Randomized trials, such as the INSTEAD-XL study, have reported higher rates of thrombosis in the FL
during follow-up in uncomplicated patients who underwent TEVAR compared to those who received
medical therapy alone. Additionally, there was a decrease in aortic-related mortality in the TEVAR
[33]
group . Despite these findings, the use of pre-emptive TEVAR in uncomplicated aTBAD remains a subject
of debate and controversy.

IMH - intramural hematoma
Intramural hematoma (IMH) is characterized by the presence of blood within the aortic wall. It is believed
to occur as a result of ruptured vasa vasorum within the tunica media or as a consequence of aortic
dissection (AD) with thrombosis of the FL and without a detectable entry tear [34,35] . IMH has been described
in the literature as a precursor or even a subtype of AD, indicating a close relationship between the two
conditions [36,37] .

Similar to AD, IMH is also classified using the Stanford classification system. Type A IMH refers to cases
where the hematoma is localized in the ascending aorta, while type B IMH involves the aortic arch and/or
the descending thoracic aorta (DTA) without the involvement of the ascending aorta.

Management
In cases of Intramural Hematoma (IMH), it is possible to refer to the guidelines for aortic dissection (AD)
for the corresponding segment of the aorta. Type A IMH is considered a cardio-thoracic emergency and
requires prompt open ascending aortic repair [38,39] . On the other hand, Type B IMH can be either
uncomplicated or complicated. A complicated IMH is characterized by refractory chest and/or back pain,
progressive hematoma expansion, pleural effusion, or aortic rupture [36,37] .

Patients with uncomplicated Type B IMH are typically managed medically, following a similar approach as
with aTBAD. However, in cases of complicated Type B IMH, a non-conservative management strategy is
recommended. Currently, endovascular repair with thoracic endovascular aortic repair (TEVAR) is
[40]
preferred over open surgery for patients with favorable anatomy . Many authors suggest complete
coverage of the IMH lesion with the stent-graft, ensuring an ideal > 20 mm proximal and distal landing zone
of healthy aorta. A maximal oversize of 10% is commonly advocated [41-44] . However, some authors propose a
less extensive aortic coverage, with incomplete distal coverage of IMH, particularly in patients with large
[42]
patent critical intercostal arteries . IMH usually do not extend below the diaphragmatic aorta, and
adjunctive procedures for visceral branch involvement may be less necessary compared to AD. It is
important to note that patients with IMH exhibit a similar aortic frailty as seen in AD, and complications
such as retrograde Type A AD (RAD) and stent-graft induced new entry tears (SINE) may also occur in this
setting. Therefore, a cautious approach is advised during procedural planning, including reduced oversizing,
avoidance of ballooning, and the use of stent-grafts without barbs and low radial force [36,37] .

Notably, medical therapy alone has shown high failure rates in the treatment of IMH, with only 10% of
patients experiencing regression. IMH frequently evolves into classic AD (28%-47%) or aortic rupture
(20%-45%) . Several radiological signs have been identified as potential predictors of failure of medical
[42]
therapy, such as IMH thickness > 8 mm and aortic diameter > 55 mm. In these cases, many authors
recommend considering endovascular management, even in the absence of complications [42,45] . Close
imaging surveillance using magnetic resonance imaging (MRI) or computed tomography (CT) is therefore
recommended [Figure 6].