Key Words
Aortic dissection - Aortic surgery
Introduction
Aortic intramural hematoma (IMH) is pathologically distinct from aortic dissection,
characterized by hemorrhage into the aortic media in the absence of an intimal tear
and direct flow communication between the true and false lumens. Krukenberg[1] suggested that rupture of the vasa vasorum initiates the process of IMH. Gore suggested
that medial degeneration predisposes the vasa vasorum to rupture and hemorrhage[2].
The management of acute Stanford Type A intramural hematoma (IMH) of the aorta remains
controversial. Most surgeons advocate emergency surgery in a manner similar to frank
acute Type A dissection. Others recommend a conservative approach to this distinct
clinicopathological entity. We describe a patient with acute Type B aortic pathology
mimicking Type A IMH with organ malperfusion that was successfully managed by thoracic
endovascular aortic repair (TEVAR).
Case Presentation
A 56-year-old white female with a history of hypertension, heavy smoking, and chronic
obstructive pulmonary disease was admitted to another hospital complaining of severe
chest and abdominal pain. Electrocardiogram showed nonspecific ST-T changes. Initial
troponin I levels were within normal limits. The patient was transferred immediately
for cardiac catheterization with a presumed diagnosis of acute coronary syndrome.
Coronary catheterization demonstrated external compression and distortion of the left
main coronary artery with no discrete coronary stenoses. The patient was transferred
to the acute cardiac care unit where 2-D echocardiogram showed moderate-to-severe
left ventricular dysfunction, normal right ventricular function, no significant valvular
abnormalities, and suspected acute aortic dissection.
Shortly thereafter, the patient deteriorated into cardiogenic shock with florid pulmonary
edema. The patient was sedated and intubated, and inotropic support was initiated
and an intra-aortic balloon pump was inserted.
After stabilization, a CT angiogram of the chest and abdomen was obtained. This test
was interpreted as Type A IMH starting at the sinotubular junction and extending down
to the iliac bifurcation ([Figure 1]). The IMH was complicated by external compression of the left main coronary artery,
as well as liver, right kidney, and colon malperfusion. A large intercostal artery
was observed in the proximal descending thoracic aorta ([Figure 2]). Correspondingly, metabolic acidosis and marked elevation of liver enzymes and
international normalized ratio (INR), were observed. Cardiac surgery consult was obtained,
but the patient was deemed to be too ill to undergo a major aortic procedure. The
initial course was further complicated by Gram-negative sepsis, likely originating
from a right lower lobe pulmonary infiltrate. At this time point, this desperately
ill patient was transferred to our care.
Figure 1. CT angiography axial view demonstrating the aortic intramural hematoma in the ascending
and descending aorta (yellow arrows).
Figure 2. CT angiography coronal view demonstrating the intramural hematoma, large intercostal
artery (upper green arrow) and unperfused right kidney (lower green arrow).
After initial stabilization, to better strategize treatment plan, we elected to repeat
the imaging studies, 5 days after initial presentation. A transesophageal echocardiogram
showed moderate left ventricular dysfunction, moderate aortic insufficiency, extensive
Type A IMH, and a large left pleural effusion. Repeat CT angiography demonstrated
stable hematoma in the ascending aorta ([Figure 3]), a newly developed pseudoaneurysm originating within an intimal ulcer in close
proximity to the noted large intercostal artery in the proximal descending aorta ([Figures 4] and [5]) and a new large pleural effusion.
Figure 3. CT angiography axial view demonstrating the pseudoaneurysm (yellow arrow) with extravasation
of dye into the hematoma.
Figure 4. CT angiography coronal view demonstrating the pseudoaneurysm (yellow arrow) at the
site of the intercostal branch seen in [Figure 2].
Figure 5. CT angiography 3D reconstruction demonstrating the aortic pseudoaneurysm (black arrow)
at the level of the pulmonary artery bifurcation.
The diagnosis was revised to acute Type B aortic pathology with proximal and distal
extension, and we elected to proceed with TEVAR aiming to exclude the intimal tear.
Using routine endovascular techniques, a 26×100 mm C-Gore Tag-R Type (W L Gore & Assoc.
Inc. Flagstaff, AZ, USA) stent was successfully implanted via the left femoral artery.
Due to the fact that the procedure was performed in an acute dissection phase, the
balloon at both ends of the stent was not inflated, and an oversized stent was not
used.
The patient was extubated 3 days after the procedure. The patient fully recovered
and was discharged home on the thirteenth postoperative day. Pre-discharge CT angiography
showed a well-positioned stent graft, no endoleak, and marked decrease in the ascending
aortic IMH as well the descending aortic pseudoaneurysm. Thirteen months after surgery,
the patient is asymptomatic. Follow-up CT angiography showed complete resolution of
the IMH, elimination of the intimal ulcer and remodeling of the pseudoaneurysm ([Figures 6], [7], and [8]).
Figure 6. CT angiography axial view 9 months after the procedure: the intramural hematoma had
resolved, and the stent graft is seen in the descending aorta.
Figure 7. CT angiography coronal view 9 months after the procedure, demonstrating the stent
graft in the descending aorta and the disappearance of the aortic pseudoaneurysm.
Figure 8. CT angiography 3D reconstruction 9 months after the procedure, demonstrating the
stent graft in the descending aorta and the disappearance of the aortic pseudoaneurysm.
Discussion
Emergency surgery is nearly always recommended in patients with acute Type A aortic
pathology and organ malperfusion. The most important principle of surgical repair
of typical Type A dissection includes resection and reconstruction of the aortic segment
containing the intimal tear initiating the dissection. This is most commonly achieved
via a median sternotomy using deep hypothermia and circulatory arrest. Due to very
high mortality and morbidity associated with this approach, an alternative strategy
comprised of emergency percutaneous or open distal aortic fenestration, followed by
delayed complete repair, was described[3]. The latter approach re-establishes organ perfusion, allowing the patient to recover
and reach the complete repair in a much better condition. By definition, this strategy,
however, is not applicable in Type A IMH due to lack of proximal intimal tear. Our
patient was, therefore, considered for an open conventional repair, but deemed too
ill. Repeat imaging was highly suggestive that the site of origin of the acute aortic
pathology was, in fact, a locus minoris adjacent to a large intercostal artery in
the proximal descending aorta. We therefore, elected to exclude the site using standard
endovascular techniques. To minimize the risk of spinal cord injury, we covered only
the suspicious segment. Two other important technical considerations included avoidance
of stent-graft oversizing and balloon dilation[4]. TEVAR resulted in rapid clinical improvement and marked, sustained reverse aortic
remodeling.
This case underscores the importance of frequent surveillance imaging in patients
with acute aortic pathology treated medically (rather than surgically) aiming to better
define the pathology and/or identify interval changes suggestive of pending rupture.
In the current case, it enabled us to identify a very uncommon event of organ malperfusion
secondary to retrograde and antegrade extension of IMH originating from a Type B aortic
pathology. This resulted in a dramatic shift in the operative strategy to a much less
invasive approach of TEVAR.
