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Page 8 of 16 Trahanas et al. Vessel Plus 2022;6:49 https://dx.doi.org/10.20517/2574-1209.2021.125

dissection (who have stable and thickened dissection flaps and distal fenestrations that pressurize the false
lumen). A small single-center study from Duke University placed implantable pressure monitors into the
proximal thoracic false lumen at the time of TEVAR for CTBAD and demonstrated a significant reduction
[17]
in pressurization of the proximal thoracic false lumen after primary tear coverage with TEVAR . Other
series from multiple centers have also demonstrated false lumen thrombosis and beneficial positive thoracic
aortic remodeling when CTBAD is treated with TEVAR, with excellent procedural and survival outcomes.
TEVAR has been shown to have a lower peri-procedure morbidity and mortality, albeit with a higher
reintervention rate, when compared to open surgery [17,24,32-34] . These findings have also been confirmed in a
large meta-analysis of open vs. endovascular intervention for CTBAD . If false lumen perfusion persists
[20]
after TEVAR, embolization and other endovascular occlusion procedures have been successful in
[35]
promoting thrombosis of the false lumen .
Open surgical intervention
Open surgical intervention is the treatment of choice for patients with connective tissue disease or anatomy
[2]
(typically TAAA) that is unsuitable for TEVAR . The extent of the aneurysmal degeneration will determine
the design of the operation needed for repair, and Dr. Stanley Crawford developed the currently utilized
classification scheme of TAAA based upon the longitudinal extent of aneurysmal involvement . Extent I
[22]
TAAA spare the abdominal aorta, whereas extents II, III, and IV involve the abdominal aorta, with extent II
being the most extensive [Figure 4]. The Safi modification adds type V, which extends from the distal
thoracic aorta, including the celiac and superior mesenteric origins only (but not the renal arteries) .
[36]
In the open approach, the aneurysmal segment of the aorta is ideally replaced from non-aneurysmal aorta
proximally to normal caliber aorta distally, which may or may not be dissected. If dissection is present in the
distal aorta at the anastomotic site, the distal dissection membrane may be fenestrated to allow perfusion of
any branches being supplied by the false lumen. If no major branches rely on false lumen flow, the false
lumen can be obliterated in the suture line. If dissected aorta remains after open repair, then the risk of
subsequent aneurysmal degeneration distal to the anastomotic site remains as well . In fact, even after open
[9]
procedures, studies have shown 12% of patients require late additional intervention for subsequent
aneurysmal degeneration .
[20]

Regarding the conduct of the operation, there are a wide variety of techniques and strategies available to
accomplish the surgical resection safely. The simplest and oldest is the “clamp and sew” technique
popularized by Dr. Stanley Crawford . Due to the risk of organ ischemia, it has become widely accepted
[22]
that intraoperative protection strategies should be considered in nearly all patients who are having an open
repair of the DTA or TAAA [21-22] . These protection strategies include extracorporeal circulatory support,
selective perfusion of visceral and large branch arteries, neurophysiologic intraoperative monitoring, and
cerebrospinal fluid drainage .
[21]
Extracorporeal circulatory support can be accomplished via left heart bypass (LHB), partial
cardiopulmonary bypass (CPB), and full CPB with or without systemic cooling. The benefit of LHB is lower
heparinization, but at the disadvantage of having to clamp the aorta to complete the proximal anastomosis,
which may necessitate greater surgical dissection and risk damaging surrounding nerves and structures.
Additionally, because the heart is relied upon to perfuse the upper body during LHB, systemic cooling
cannot be initiated due to the risk of ventricular fibrillation. Individual perfusion catheters can be used in
the ostia of the visceral vessels to maintain some organ perfusion during the period of visceral ischemia
[22]
[Figure 5].