Keywords aortic dissection - malperfusion - hybrid arch repair
Introduction
Up to one-third of cases of acute type A aortic dissection (ATAAD) and 25% of acute type B aortic dissection (ATBAD) cases are complicated by malperfusion syndrome, which is considered an independent predictor of early mortality.[1 ] The optimal timing and management strategy for such malperfusion is unclear, in part due to its heterogeneous and dynamic nature.[2 ] While resection of the primary entry tear and graft replacement of the ascending aorta remain the cornerstone of ATAAD management, this is not always sufficient to adequately resolve the concurrent malperfusion syndrome. In such cases, a more extensive repair or additional procedures are required. We hereby present a case of ATBAD with retrograde extension to the ascending aorta, with the most proximal intimal tear located in the descending thoracic aorta, complicated by preoperative lower extremity malperfusion and postoperative delayed mesenteric malperfusion, in which we opted for an open fenestration of the femoral artery, zone 2 arch repair, and subsequent thoracic endovascular aortic repair (TEVAR) which proved to be an effective method to treat this highly lethal combination of events.
Case Presentation
A 60-year-old man was admitted to the Emergency Department complaining of acute pain in his left lower limb, which showed signs of severe hypoperfusion and partial loss of motor function. A computed tomography (CT)-angiogram showed aortic dissection extending from the ascending aorta to the femoral arteries, with the most proximal intimal tear located in zone 3, just distal to the origin of the left subclavian artery (LSA; [Fig. 1A ]), which can be classified as a type B0,12 according to the recent Society for Vascular Surgery/Society of Thoracic Surgeons (SVS/STS) reporting standards.[3 ] The brachiocephalic, left carotid, coeliac, superior mesenteric, and right iliofemoral arteries originated from both lumina, and the left iliofemoral trunk was almost completely obliterated ([Fig. 1B ]). The origin of the celiac trunk and superior mesenteric artery (SMA) are shown in [Fig. 2A ].
Fig. 1 Preoperative computed tomography (CT) scan. (A ) The most proximal intimal tear is seen in the descending thoracic aorta. (B ) Partial occlusion of the iliofemoral trunk.
Fig. 2 Mesenteric malperfusion treatment. (A ) Postoperative computed tomography (CT) scan showing dynamic obstruction of the celiac trunk and superior mesenteric artery (SMA). (B ) Intraoperative angiography showing a patent left carotid-to-subclavian bypass and TEVAR deployment distally to the new common brachiocephalic/left carotid trunk. (C ) Postendovascular procedure CT scan showing celiac trunk and SMA patency. TEVAR, thoracic endovascular aortic repair.
The patient was immediately taken to the operation room, where open embolectomy and direct fenestration of the left common femoral artery were carried out, with immediate visible reperfusion of the limb. Concurrently, a median sternotomy was performed and a cardiopulmonary bypass was instituted via direct cannulation of the ascending aorta (with ultrasound guidance), with a Y-connected to an 8-mm Dacron interposition graft on the common femoral artery for perfusion of the left lower limb. Hypothermic circulatory arrest at 25 °C and bilateral antegrade selective cerebral perfusion were used. A supra-coronary ascending aorta and zone 2 aortic arch replacement with a 28-mm Dacron graft were performed, with reimplantation of the brachiocephalic and left carotid arteries as a common trunk, since the patient had a bovine arch. A 25-mm landing zone was left between the newly implanted common trunk and the distal suture line for future endovascular treatment.
Completion of the procedure to exclude the causal intimal tear in zone 3, by left carotid-to-subclavian bypass and TEVAR, was planned at a later stage as a preemptive measure, given the fact that the CT scan showed some compression of the true lumen at the level of the celiac trunk and SMA, risking visceral malperfusion. Nevertheless, a few days after the initial surgery the patient developed paralytic ileus with nausea and abdominal pain. A CT-angiogram showed gaseous distention of the small bowel and gastric fluid accumulation, along with hypoperfusion of the celiac trunk and the SMA. No signs of advanced bowel ischemia were yet found since the bowel wall contrast enhancement was still normal. Therefore, the decision was taken to complete the procedure, as planned, on an emergency basis, by left carotid-to-subclavian bypass followed by TEVAR with a 34 × 200 mm GORE TAG (W. L. Gore & Associates, Flagstaff, AZ) endograft, with the proximal landing zone located just distally to the new common trunk and distal landing zone at the mid-descending thoracic aorta. The origin of the LSA was occluded with a 12-mm Amplatzer Vascular Plug (St. Jude Medical, St. Paul, MN) before the implantation of the endograft. Balloon dilatation of the endograft was required at the level of zone 3, due to incomplete expansion. Spinal cord drainage was not used due to the emergency setting. Celiac trunk and SMA patency were confirmed by intraoperative angiography ([Fig. 2B ]) and postoperative CT scan, showing expansion of the true lumen, reduction of the false lumen, and good perfusion of the two vessels ([Fig. 2C ]). The remainder of the postoperative course was uneventful, and the patient was discharged after 12 days. The 3-month follow-up CT scan showed stable diameters, although false lumen patency persists.
Discussion
Malperfusion is present in up to one-third of patients with ATAAD and 25% of ATBAD. Malperfusion is considered an independent predictor of early mortality, which is reported to range up to 50%, depending on the number of affected organ systems and the management strategy.[1 ]
[2 ] Also, preoperative lower extremity malperfusion is considered an independent predictor of early mortality (OR: 1.43; 95% CI: 1.01–2.01; p = 0.042), as well as postoperative mesenteric malperfusion (OR: 3.24; 95% CI: 1.94–5.35; p < 0.001).[1 ] In selected cases, early reperfusion strategies, either by open or endovascular treatment, in addition to a central aortic repair, have been demonstrated to improve outcomes.[4 ]
[5 ] In our reported case, the left lower extremity malperfusion syndrome was treated by open surgical repair of the obliterated left femoral artery, as described, allowing for early restoration of the blood flow in both lumina.
The presence of an intimal tear located in the descending aorta makes the choice of distal aortic repair more complex. Furthermore, it has been reported as an independent predictor of postoperative mesenteric malperfusion by the GERAADA investigators.[1 ] In this case, in order to exclude the intimal tear, we planned a two-step hybrid procedure, by zone 2 arch repair with reimplantation of the first two aortic arch vessels, associated with deferred left carotid-to-subclavian artery bypass and TEVAR. As a matter of fact, standard hemiarch repair does not directly address arch or descending aorta tears and does not create a landing zone for later TEVAR.[6 ] Zone 2 hybrid arch repair creates an ideal artificial proximal landing zone for subsequent endovascular procedures. Moreover, if compared to the frozen elephant trunk technique in the emergency setting, simplifying the arch procedure and deferring the TEVAR reduce both circulatory arrest time and the risk of spinal cord injury,[7 ] augmented by the beneficial association of left carotid-to-subclavian bypass, as demonstrated by the 4-territory concept.[8 ]
Regarding the mesenteric malperfusion, the preoperative CT scan already showed compression of the true lumen at the level of the coeliac trunk and SMA, but no clinical signs of malperfusion were present. The delayed-onset malperfusion syndrome that emerged a few days after surgery was caused by dynamic obstruction of the celiac trunk and SMA, therefore we decided to treat it promptly by early completion of the planned procedure, thus avoiding irreversible ischemic damage, which is associated with a dismal prognosis. Other options can be considered for the treatment of delayed malperfusion, such as endovascular fenestration, however, that approach does not avoid later aneurysmal degeneration of the untreated dissected aorta.
Conclusion
Zone 2 arch repair represents an optimal treatment choice for ATAAD and ATBAD with retrograde extension to the ascending aorta, especially in younger patients, allowing the creation of an artificial proximal landing zone for future TEVAR in case of aneurysmal degeneration of the distal arch and descending thoracic aorta. Additionally, this case clearly displays that, in selected cases, this strategy allows for an expeditious and effective treatment of delayed malperfusion syndrome.
