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Page 2 of 9 Lou et al. Vessel Plus 2022;6:38 https://dx.doi.org/10.20517/2574-1209.2021.108

to optimize treatment. The conventional management of acute type A aortic dissection (ATAAD) with or
without malperfusion is emergent central aortic repair, which involves a hemiarch replacement with the
addition of a total arch replacement for patients with pre-existing arch aneurysms, primary intimal tears
identified in the distal arch or descending thoracic aorta, and/or evidence of visceral or peripheral extremity
malperfusion. However, evidence has been gradually accumulating to suggest a potential benefit for initial
reperfusion of distal organs using endovascular techniques followed by central aortic repair. This approach
has been fueled by the success of thoracic endovascular aortic repair (TEVAR), which is now regarded as
the gold standard in the treatment of complicated acute type B aortic dissection (TBAD) with malperfusion.

This focused review highlights the pathogenesis and challenges in management, provides an overview of
malperfusion syndromes by organ systems, and addresses the ongoing areas of controversy and new
frontiers in the treatment of acute aortic dissection with malperfusion. ATAAD complicated by mesenteric
malperfusion (MMP) has historically portended the worst outcomes, and its management has undergone
the most flux in recent years. Therefore, we will focus the latter part of our discussion on the evolving role
of end-organ revascularization first followed by central aortic repair.

CLINICAL DEFINITIONS
When discussing end-organ malperfusion, it is first necessary to establish the clinical definition of
malperfusion vs. malperfusion syndrome. Malperfusion itself is defined as inadequate end-organ perfusion,
secondary to dissection-related obstruction of the aorta and its branch vessels. This can result from multiple
[1]
mechanisms of obstruction, categorized as dynamic, static, or both .

The relationship between the mobile septum and the true lumen is complex. In dynamic obstruction, the
repetitive motion of the intimal flap within the aortic lumen covers and protrudes into branch vessel ostia to
an end-organ resulting in ischemia. This mechanism is the most common cause of malperfusion (80%) and
[2]
results in variable symptoms given the dynamic nature of the occlusion . Static obstruction occurs when
the dissection flap continuously occludes the branch vessel ostia or the branch vessel dissects and extends
distally. The mechanism of obstruction, static vs. dynamic, dictates the treatment strategy, with dynamic
generally resolving with medical management of hemodynamics and central aortic repair. In contrast, static
malperfusion generally requires some form of additional intervention to treat in addition to central aortic
repair.

Later stages of end-organ malperfusion result in malperfusion syndrome, characterized by necrosis and/or
end-organ dysfunction. As a syndrome, it entails a set of clinical, laboratory and radiographic findings as
described below:
• Clinical features (e.g., abdominal pain, hematochezia, pulselessness, loss of motor function, oliguria);
• Laboratory findings (e.g., lactic acidosis, elevated liver and pancreatic enzymes, elevated creatinine);
• Radiographic findings of dynamic or static obstruction resulting in absent or decreased flow to the organ.

PATHOGENESIS AND CHALLENGES
Malperfusion syndrome itself results in an inflammatory cascade resulting from end-organ ischemia,
increased myeloperoxidase production, and complement consumption. Free radical generation through
neutrophil activation in ischemic tissue mediates endothelial injury and compromises membrane integrity.
The downstream upregulation of TNF-alpha and IL-1 results in a positive feedback loop, which is mediated
by leukocyte extravasation and cytokine release, leading to further end-organ injury. Thus, the
inflammatory cascade brought on by end-organ ischemia significantly impairs clinical outcomes even after
successful operative repair of the dissection .
[1]