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Geragotellis et al. Vessel Plus 2023;7:6 https://dx.doi.org/10.20517/2574-1209.2022.41 Page 3 of 12

[1]
Figure 1. Illustration depicting the aortic arch’s different Zones (0-4). Original figure. Reused from Choudhury et al. .

Overview of clinical outcomes with Z-2-FET
The increasing popularity of Zone 2 distal anastomosis in FET is manifested in the recent data
demonstrating its efficacy. The Pennsylvania group achieved successful thoracic false lumen (FL)
[9]
obliteration in 80% of cases, with 17% complete thromboses . Findings from Chen et al. echo this success,
with three-month computed tomography surveillance showing FL obliteration in 91.7% of acute DeBakey 1
dissections .More recent data from a Chinese single-centre study showed similar positive results, with FL
[10]
thrombosis confirmed on imaging in 92.3% of patients treated for acute type B dissection (TBAD) . In
[11]
their 148-patient series, Sun et al. reported an in-hospital mortality of 4.7% for patients undergoing Z-2-FET
[12]
for type A aortic dissection (TAAD), with 99% of lesions remaining free from reoperation . Other series
have been described equally as encouraging success, while groups in Japan and China have reported zero
deaths in their studies [11,13] . Generally, the mortality rates in the literature range from 4.2%-14.3% [9,10,12,14-19] .

Upon searching independent Z-2-FET studies within the literature, neurological outcomes were similarly
encouraging, with numerous studies reporting zero incidences of clinically relevant spinal cord injury
(SCI) [15,17,19] . However, more extensive series, including that from the Bologna group , have described the
[20]
incidence of spinal cord injuries at about 5%. Stroke, however, remains a significant potential complication
of FET, with the reported postoperative rates being 1.9%-10.7% [9-15,17,18] . Augmentations to surgical
techniques and neuroprotective protocols are expected to ameliorate these neurological outcomes. Factors
beyond the distal anastomosis site will influence clinical practice’s neurological and mortality/morbidity
outcomes. Significant factors are the complexity and severity of the underlying pathology and the surgical
approach adopted (supra-aortic vessel re-implantation and LSA revascularisation).

ZONE 3 FROZEN ELEPHANT TRUNK
Z-3-FET technicalities
The surgical approach in Z-3-FET involves a deeper aortic arch resection distal to the origin of LSA.
Manipulation of the arch at Zone 3 poses more technical challenges due to its anatomic position deep
[1]
within the chest . Furthermore, FET implantation at Zone 3 requires a more extensive dissection of
surrounding structures, which increases the risk of inadvertent damage to the recurrent laryngeal nerve
(RLN) . Similar to Z-2-FET, different surgical approaches to Z-3-FET for re-implantation of the supra-
[21]
aortic vessels exist . However, increased surgical complexity associated with Z-3-FET precipitates longer
[1]
hypothermic circulatory arrest and CPB durations, which may increase the risk of neurological injury,
[7]
visceral ischaemia, and renal complications . Nevertheless, it is essential to note that the choice of the Z-3-