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

thoracoabdominal incision and the necessity for single-lung ventilation make preoperative pulmonary
[21]
function assessment particularly important . Every effort should be made to medically optimize a patient
prior to this intervention, and all organ systems should be evaluated. Echocardiogram, electrocardiogram,
right and left heart cardiac catheterization, pulmonary function testing, complete metabolic panel and liver
function testing, and CTA of the entire arterial tree are just a few of the preoperative tests that may be
[22]
necessary . Patients with prior abdominal or retroperitoneal surgery, large abdominal hernia, morbid
obesity, and poor cardiopulmonary reserve are often unfit for open DTA or TAAA repair. While TAAA
repair falls outside of the scope of STS preoperative risk calculator, this tool may be used to quantify patient
co-morbidities.

TEVAR may offer a less morbid procedure and has been shown to be durable in the mid-term ; however,
[23]
the long-term durability of these devices is unknown. Ideal candidates for TEVAR have the aneurysmal
component limited to the descending aorta with the entry tear distal to but not involving the left subclavian
artery . Patients with a distal descending diameter of > 4.2 cm at the celiac axis are generally not candidates
[2]
for standard TEVAR . In a study of TEVAR for CTBAD, a 15% incidence of complete resolution of the
[2]
thoracic and abdominal false lumen was observed in those treated with TEVAR. It should be noted that all
these patients with complete false lumen resolution had the four visceral vessels fed by the true lumen and
[24]
less than three distal (abdominal, iliac) residual fenestrations . Greater than five distal fenestrations in the
abdominal aorta and iliac arteries increase the risk for late aneurysmal degeneration of the abdominal aorta,
[24]
even after treatment . These anatomical features are therefore critical when considering which
intervention strategy to offer. A tortuous and angulated aorta, or small and heavily calcified common
femoral and iliac arteries, may also exclude TEVAR as an option. Occasionally an iliac or abdominal aortic
[23]
conduit may be required for access .

Endovascular intervention
If TEVAR is planned for CTBAD, it is important to consider the proximal and distal landing zones, the
extent of the aorta to be covered, and the access vessels. Proximally, a 2 cm landing zone proximal to the
primary tear is desired. Although the proximal landing zone ideally should involve non-dissected aorta, the
procedure can still be successful in many cases if a portion of the proximal landing zone is dissected, as may
be seen in the case of a primary tear distal to the left subclavian artery. The average diameter measured via
centerline technique in the undissected segment should be used to size the proximal portion of the
[2]
endograft . If required for adequate sealing, the origin of the left subclavian can be partially or fully covered
and selectively revascularized based upon whether there is the preservation of pulsatile antegrade flow [2,25-27] .
The location of distal fenestrations by thin-cut CTA should be studied preoperatively, and intravascular
ultrasound (IVUS) can be useful for identifying them intraoperatively.

Operators should have a low threshold to cover the entire descending thoracic aorta down to the level of the
celiac axis to eliminate distal fenestrations. In contradistinction to the proximal landing zone, the distal
landing zone should be sized only to the true lumen to avoid stent graft-induced new entry tear (SINE)
from excessive device oversizing relative to the small distal true lumen. Unlike acute type B dissection,
where endograft deployment is always proximal to distal, in the setting of CTBAD, endograft deployment is
often distal to proximal (so-called “distal first technique”). Larger proximal endografts can be placed to
overlap inside distal smaller segments to minimize the risk of SINE [2,4,28] . CTA imaging can help guide the
choice of access site, and IVUS is indispensable in confirming wire access of the true lumen .
[2]
Intraoperative transesophageal echocardiography and IVUS also help to assess the position and expansion
of the endografts after deployment and rule out complications such as retrograde type A dissection
[2]
[Figure 3].