Key Words Aortic dissection - Subclavian artery - Ischemia
Introduction
End-organ malperfusion and ischemia is not uncommon in acute DeBakey Type I dissection.
Traditionally, proximal aortic repair has been undertaken first, and remaining end-organ
ischemia, if any, has been managed postoperatively. However, if arterial obstruction
is judged static, rather than dynamic, and unresolving ischemia is anticipated, it
may be justified to address ischemia without delay, i.e., intraoperatively, to mitigate
its effects.
Case Presentation
The patient, a previously healthy 61-year-old man, was admitted to another hospital
with sudden chest pain and left leg ischemia: pain, numbness, pulselessness and loss
of motor control. A computed tomography (CT) scan demonstrated acute aortic dissection
Stanford Type A/DeBakey Type I with subtotal occlusion of the right carotid artery
([Fig. 1 ]) and left external iliac artery ([Fig. 2 ]). Clinically, the dissection was classified as Penn Ab[1 ]. Suspecting static occlusion, due to local false lumen thrombosis, rather than dynamic
occlusion, due to mobile dissection flap, it was decided to address the malperfusion
of the left leg directly. At operation, simultaneously with sternotomy and cannulation,
a femoro-femoral crossover bypass using an 8-mm Dacron graft was performed ([Fig. 3 ]), with immediate restoration of peripheral regional tissue saturation as monitored
by near-infrared spectroscopy (INVOS™, Covidien, Boulder, CO, USA). In addition, a
prophylactic three-compartment fasciotomy of the lower leg was carried out. Arterial
cannulation was performed in the only nondissected peripheral vessel, the left subclavian
artery ([Fig. 1 ]), using an 18 French Fem-Flex II (Edwards Lifesciences LLC, Irvine, CA, USA) cannula
introduced by modified Seldinger technique[2 ]. The ascending aortic repair was carried out in a standard fashion, using a supracoronary
straight 28-mm tube-graft with a side-arm, a hemiarch distal anastomosis during deep
hypothermia (18°C), and circulatory arrest followed by side-arm recannulation, reperfusion,
and rewarming. Apart from implantation of a permanent pacemaker due to intermittent
AV-block, the postoperative course was uneventful. At radiological follow-up three
months postoperatively, the ascending aortic repair is satisfactory, the right carotid
artery is patent with less false lumen thrombosis, the left external iliac artery
remains subtotally occluded ([Fig. 4 ]), and the crossover bypass is widely patent with a right-to-left flow verified by
duplex sonography.
Figure 1. Preoperative computed tomography scan of the aortic arch with intravenous contrast,
reformatted image, highlighting subtotal occlusion of right carotid artery compressed
by the false lumen (black arrowhead ). Note left subclavian artery take-off from true lumen.
Figure 2. Preoperative computed tomography scan of the aortic bifurcation with intravenous
contrast, reformatted image, highlighting occlusion of left external iliac artery
with false lumen thrombosis (white arrow ). Note patent but dissected right common iliac artery (white arrowhead ).
Figure 3. Intraoperative photograph demonstrating the finished femoro-femoral crossover bypass
(white arrowheads ), the exposed heart and dissected ascending aorta (white arrow ), and the left subclavian artery cannulated from a separate incision (black arrowhead ).
Figure 4. Postoperative computed tomography scan of the pelvic region with intravenous contrast,
reformatted image, demonstrating persisting left external iliac artery occlusion (black
arrows ) and patent femoro-femoral crossover bypass graft (white arrowhead ).
Discussion
The treatment of leg malperfusion and ischemia at presentation has regularly been
postponed until after the ascending aortic repair[3 ]. In cases of dynamic obstruction, it is reasonable to assume that dissection repair
and reestablishment of preferential true lumen blood flow is sufficient to restore
leg perfusion, and ischemia can resolve. However, if the obstruction is static (or
combined), delaying intervention until after aortic repair may only propagate further
ischemic damage, contributing to the increased mortality and morbidity associated
with end-organ ischemia[1 ]
[4 ]. Performing a simultaneous crossover bypass is a quick and simple solution with
high success rate. The only modification of the dissection operation is refraining
from femoral arterial cannulation. The described strategy of selective leg perfusion[5 ] adds no further benefit in a similar situation, still mandating a revascularization
of the affected leg in a postponed or secondary procedure. Endovascular treatment
using bare metal stent or stent-graft would either delay the aortic repair (if performed
preoperatively), delay leg reperfusion (if performed postoperatively), or demand a
hybrid operating suite for the two procedures to be performed simultaneously, along
with the cost of the device(s), the need for antithrombotic medication, and the risk
of future secondary intervention.
Although outside of manufacturer instructions for use, peripheral INVOS™ tissue saturation
monitoring is quick, simple, and probably satisfactory in assessing immediate revascularization
outcome and limb reperfusion[6 ].
