DISCUSSION
The present study revealed that this revascularization-first strategy for mesenteric malperfusion was reasonable and feasible. Patients who underwent revascularization-first strategy recovered without any mesenteric ischemic events, whereas those who underwent central repair-first strategy developed paralytic ileus.
Despite improvement of in AAD management, organ malperfusion can be critical.1 Specific mesenteric malperfusion rates were reported between 1.4% and 8.2%.3 Among ischemic end-organ complications occurring at the onset of dissection, mesenteric malperfusion is one of the most insidious and challenging complications to manage.1, 2
The classic treatment algorithm in AAD was to close the proximal entry tear and to reestablish peripheral true lumen perfusion.4, 6, 7 However, primary surgical repair of the entry site can add trauma to the already-ischemic organs, and the ensuing uncontrolled reperfusion usually ends in patient death. Recent reports have reported paradoxical results. Kamman et al. described that surgical delay in malperfusion cases was significantly associated with lower mortality rates.3 They recommended relief of branch vessel obstruction first, followed by urgent aortic repair only when the malperfusion syndrome and its sequelae were resolved.3Deeb et al. also recommended delaying surgery for primary distal reperfusion and stabilization.5 Tsagakis et al. proposed the hybrid OR concept prioritizing revascularization of malperfusion.6, 7 Thus, the authors emphasized the controversial paradigm of mesenteric revascularization-first approach using IVR prior to the central repair to alleviate metabolic crisis.
Malperfusion has two types of pathophysiology, namely, dynamic and static. Dynamic malperfusion is defined as dissection with compression of the true lumen owing to false lumen pressurization with resulting flap occlusion of the orifice of the branch vessel.3Static malperfusion is defined as dissection of the branch vessel with obstruction of the true lumen. In most cases, this is related to thrombosis of the false lumen with compression and obstruction of the true lumen.8 Static malperfusion may require initial intervention with stenting of the branch orifice or bypass for timely reperfusion.9 Previously, an aortic dissection with dynamic malperfusion may be treated with a central repair to entry closure.9 However, whether it is a dynamic or static malperfusion is usually unclear preoperatively. Furthermore, in many cases, a combination of a static and a dynamic component is present.3 Moreover, we should be cautious that malperfusion may worsen because the dissection flap extending into the branch changes after the central repair.9 Basically, in our institute, revascularization-first strategy is chosen for any type of malperfusion.
In accordance with Tsagakis et al., even in patients with initial circulatory instability due to tamponade, invasive diagnostics and treatment for organ malperfusion is possible in hybrid OR after cautious tamponade release and pericardial drainage under blood pressure control.6, 7 Tsagakis et al. have proposed that revascularization of malperfusion should be considered after cardiac drainage in hybrid OR even after full sternotomy.6, 7In the present study, central repair was prioritized in two cases because they were hemodynamically unstable. Even in hemodynamically unstable cases, immediate tamponade release via median sternotomy or cautious pericardial drainage placement should have been considered. After attaining hemodynamic stability, IVR should have been prioritized, followed by central repair. However, in a hemodynamically compromised case with free rupture or cardiopulmonary resuscitation, central aortic repair is inevitable. Moreover, in a case with cerebral or cardiac malperfusion, revascularization for them should be performed first. Therefore, the strategy for these severely complicated cases is still controversial.
In the 1990s, percutaneous techniques were introduced to restore end-organ perfusion and reduce morbidity associated with open surgical repair in a complex and high-risk patient cohort of AAD.3 This approach consisted of flap fenestration and placement of a true lumen stent in the visceral artery to eliminate dynamic obstruction. IVR was less invasive than open surgical revascularization for mesenteric malperfusion.
Hybrid ORs are currently gaining popularity worldwide due to the exponential growth of transcatheter aortic valve implantation procedures. Tsagakis et al. recommended that all patients with established or suspected diagnosis of acute aortic syndrome be admitted directly from helicopter or ambulance transport to the Hybrid OR in the presence of aortic team.6, 7 The potential of this hybrid OR concept is that it enables fast online diagnostics, followed by immediate intervention and/or open surgery, particularly for hemodynamically unstable patients.6, 7 In our institute, all patients from helicopter or ambulance transport suspected of acute aortic syndrome are checked at the emergency room before transport to the hybrid OR. The hybrid OR concept enables us to eliminate time loss and represents the ideal environment for the aortic team composed of surgeons, radiologists, and cardiac anesthesiologists. Direct transport to the hybrid OR should be incorporated in our institute.
Our study is limited by several factors. First, a small number of patients were enrolled owing to the rarity of the condition. Second, it was a retrospective, single-center experience that lacked any form of randomization. Finally, the surgical technique for AAD has evolved during the time period of this study. In the future, multicenter study will be necessary to compensate for these limitations. Furthermore, global research not only domestic, should be conducted. On the other hand, in our institute, the hybrid OR concept proposed by Tsagakis et al. should be promoted. The better performance of aortic team is expected in the treatment of acute aortic syndrome.