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.