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  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 .
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).
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.
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.
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).
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 . 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 . 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.