Repair of Retrograde Type A Aortic Dissection after Thoracic Endovascular Aortic Aneurysm Repair Using the Modified Elephant Trunk Technique

Methods

A 58-year-old man with a history of hypertension, emphysema, and coronary artery disease presented to an outside facility with acute onset of chest pain radiating to his neck. Computed tomography (CT) of the chest and abdomen was performed, revealing an acute type B aortic dissection. He was admitted to the intensive care unit for medical management. On hospital day 3, the patient reported persistent back and flank pain and subsequently underwent angiography and intravascular ultrasonography, which identified right renal artery compromise owing to flap occlusion. For this reason, the patient underwent TEVAR of the descending thoracic aorta using a 37 mm × 15 cm Gore TAG Excluder (Flagstaff, AZ) with right renal artery stenting. The patient's convalescence was prolonged, requiring intense rehabilitation and physical therapy, possibly owing to noncompliance, but he was eventually discharged home after 1 month. Three weeks after discharge, the patient re-presented to the same outside facility with shortness of breath and a new onset of chest pain. Evaluation revealed no evidence of cardiac cause for the chest pain; an electrocardiogram and cardiac enzymes showed no evidence of cardiac ischemia. CT angiography was performed, this time revealing acute type A aortic dissection presumed to be retrograde in nature (Figure 1). He was subsequently transferred to our institution for management.

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Figure 1.

Computed tomographic angiogram of the chest revealing a previous thoracic stent (A) and type A aortic dissection (B).

On admission, pain control was begun, and the patient's hypertension was controlled with β-blockade (anti-impulse therapy). He was prepared for urgent repair. In the operating room, general anesthesia was administered, and transesophageal echocardiography confirmed the type A aortic dissection with associated mild aortic insufficiency. Standard arterial and pulmonary arterial monitoring was used. In addition, bilateral near-infrared spectroscopy and electroencephalography (EEG) were used for cerebral monitoring. After sterile preparation, the right common femoral artery was exposed and median sternotomy was performed. Systemic anticoagulation was given. Cardiopulmonary bypass was instituted via the right common femoral artery and superior and inferior vena cava, with no inappropriate changes in cerebral monitoring observed during the cooling phase. When the EEG became isoelectric, which corresponded to a nasopharyngeal temperature of 15.9°C, hypothermic circulatory arrest and retrograde cerebral perfusion was commenced. On opening the ascending aorta, the previously placed thoracic endograft was identified, with its proximal attachment at the level of the innominate artery. The thoracic endograft was removed without difficulty. Thrombus was noted in both ostia of the left common carotid and left subclavian arteries. Using a #4 balloon tip catheter, thrombus was extracted from each of the ostia of the left common carotid and left subclavian arteries. Backflow of deoxygenated blood was noted from these orifices. Inspection revealed a tear (50% of the circumference of the aorta) on the posterior-lesser curve junction, 2 cm proximal to the ostium of the innominate artery. The flap did extend to the previous location of the endovascular stent. Distally in the descending thoracic aorta, a flap was identified, distal to the position of the distal end of the previous stent. The transverse arch was otherwise intact and not significantly dilated. We decided to perform a modified elephant trunk technique. A 10 cm length of a 20 mm diameter collagen-impregnated polyester graft was inserted into the descending thoracic aorta above the dissection flap. This was sutured distal to the left subclavian artery using a 3-0 polypropylene suture. The lesser curve of the transverse arch was resected. A 28 mm collagen-impregnated polyester graft with a 10 mm side arm was then cut in a beveled fashion and sutured to the remaining transverse arch using 3-0 polypropylene suture (Figure 2). Femoral flow was reinitiated, and the graft was de-aired. A new arterial line with a cannula was inserted into the 10 mm side arm, and antegrade perfusion was begun. The femoral perfusion was decreased to 500 cc/min, and systemic warming was begun. During the warming period, the proximal reconstruction was performed by resuspending the aortic valve, reconstructing the aortic root, and performing the proximal ascending graft to sinotubular junction anastomosis using 3-0 polypropylene sutures. The original aorta measured 34 mm; a 37 mm × 15 cm device was used for minimal oversizing. The patient was warmed, weaned from bypass, and decannulated, and the wound was closed.

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Figure 2.

Acute type A dissection after thoracic endovascular repair. Completed transverse arch repair with the modified elephant trunk technique.

Results

The patient awoke neurologically intact and was extubated on the second postoperative day. He developed self-limited atrial fibrillation, which was medically controlled by the fifth postoperative day. He required physical therapy and was transferred to a rehabilitation facility on the eleventh postoperative day.

Discussion

RTAAD remains a surgical challenge. It occurs spontaneously in up to 10% of all cases. ^1,2 Although a rare complication after TEVAR, RTAAD may occur in 2 to 10% of cases after TEVAR. ^9,10,12,13 Most cases have been reported during endovascular interventions for acute aortic dissection, although accounts have been reported during endovascular interventions for fusiform and saccular aneurysms, traumatic aortic injury, and cases of connective tissue disorders (Marfan syndrome). ^5,13,14 Time of occurrence with TEVAR-RTAAD has been variable, with most TEVAR-related RTAADs reported at the time of stent deployment. As in our case, delayed presentations have been observed from 1 to 124 days after stent placement. ^5,12,13 Specific factors have been suggested in the etiology of RTAAD associated with TEVAR. Suggested factors include increased rigidity of the prosthesis with too extreme aortic angulation, ⁶ open wire configuration causing intimal disruption, ^9,12,13 and tears caused by wire manipulation. ¹⁴ It is agreed, however, that predisposing medial degeneration is often associated with these cases. ¹³ As the original deployment was performed at an outside institution, and we did not have three-dimensional reconstructions from the original procedure, it was unclear whether the proximal attachment location resulted from a delayed migration (a rare possibility). No predischarge CT scan or magnetic resonance angiogram was available that might have shown the proximal location. It is uncertain whether the tear was an entry or re-entry tear. The patient had a hematoma extending from the stent, and this tear could have been a retrograde re-entry point. It would be speculation to conclude that the injury was device related.

Of the 16 patients with TEVAR-RTAAD thus reported (Table 1), 7 patients (44%) were managed nonoperatively, associated with 6 eventual deaths (mortality of 85%). The 9 patients (56%) who were managed with open surgical repair had an associated mortality of 33 to 66%. ^12,13 Thus, the mortality associated with TEVAR-RTAAD appears to be greater than that of classic acute type A aortic dissection repair.

Previous reports of repair have not provided much detail about the approach for open repair. In our report, we maintain that profound hypothermic circulatory arrest allowing an open distal anastomosis is necessary. This allows for thorough examination of the arch and easy extraction of the previous stent. Although a previous stent may be left in place and an anastomosis may be constructed to the endovascular prosthesis, ¹⁵ we felt it was better to remove the stent and place a Dacron graft in its place as the modified elephant trunk. The modified elephant trunk technique expedites future distal repair if required. It is important to keep the distal end of the elephant trunk above any fenestration so that flow is maintained in both the true and false lumen in a setting of chronic distal dissection, as in this case. Another reason for complete excision of the stent in this case was that it was occluding the left common carotid artery and left subclavian artery, and removal of the prosthesis allowed for reestablishment of antegrade flow through these vessels.

RTAAD remains a challenge. Prompt diagnosis, urgent open repair using profound hypothermic circulatory arrest, and open distal anastomosis are important for success.