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

extensive FET meta-analyses, which analysed neurological outcomes data from a total of 3154 patients from
35 studies and demonstrated that a 10 cm FET stent graft is protective against SCI compared to a 15 cm
[36]
device (2.5% vs. 11.6%; P < 0.001) . Stroke remains a concern with both Z-2-FET and Z-3-FET, although
[29]
0% stroke has been reported for Z-2-FET in the literature . Available head-to-head studies demonstrate a
permanent stroke rate of 0%-6% with Z-2-FET and between 4%-18% with Z-3-FET [8,28,29,31] [Table 2]. These
more favourable results are likely due to less coverage of the distal thoracic aorta and its branching vertebral
arteries and generally reduced ischaemic times achieved with Z-2-FET [Table 1]. Conversely, Panfilov et al.
[31]
reported improved neurological outcomes with Z-3-FET ; however, this should be interpreted with
caution based on the relatively small patient population studied.

RLN injury
The RLN loops under the aortic arch near Zones 2 and 3. Proximalisation of the surgical field improves
access to the anastomosis sites and decreases the risk of RLN damage. Detter et al. reported RLN injury in
only 3.3% of Z-2-FET patients compared to 22.6% of Z-3-FET patients (OR 0.17; 95%CI: 0.02-0.78;
P = 0.02) . Similarly, Leone et al. outlined that Z-2-FET was associated with only a 2.8% RLN injury rate vs.
[29]
5.2% seen in the Z-3-FET group (P = 0.526) . More reporting on this outcome is desirable in future studies
[8]
investigating proximalisation of the FET technique.

Respiratory outcomes
Respiratory failure post-FET is a well-recognised cause of mortality and should be considered carefully
alongside renal outcomes, given the intricately related physiology [37,38] . Two studies observed more than 40%
respiratory failure rates with Z-3-FET [28,31] . However, it remains unclear whether respiratory outcomes are
superior to Z-2-FET or Z-3-FET, as recent studies show heterogeneous results. Tsagakis et al. reported
prolonged ventilation in 19% of Z-2-FET patients vs. 43% of the Z-3-FET group (P < 0.001) . However,
[28]
Leone et al. showed significantly higher rates of tracheostomy with Z-2-FET than Z-3-FET at 11.6% vs.
7.1%, respectively (P < 0.001) . Similarly, Panfilov et al. outlined that a tracheostomy was needed in 47.7%
[8]
of Z-2-FET patients and 40.7% of Z-3-FET patients, although the sample size in this study was possibly
insufficient to bring to statistical significance (P = 0.419) .
[31]
Renal outcomes
Renal failure post-FET often necessitates temporary post-procedural dialysis. A 2020 systematic review by
Tian et al. outlined a 15.5% rate (95%CI: 11.9-20.1) of acute kidney injury postoperatively across different
aortic pathologies necessitating repair using FET . A recent systematic review and meta-analysis by Rezaei
[39]
et al. outlined that the positioning of the FET HP distal anastomosis at Zone 2 of the aortic arch was
correlated with a significantly lower occurrence of renal failure compared to Z-3-FET (OR 0.52; 95%CI:
[35]
0.33-0.82; P = 0.069; I2 = 0%) . This finding reflects the statistics outlined in Table 2, highlighting that most
of the contemporary head-to-head evidence suggests superior renal outcomes with Z-2-FET. Tsagakis et al.
demonstrated the most striking difference, who reported renal failure/dialysis of 26% with Z-2-FET vs. 43%
with Z-3-FET (P = 0.004) . This substantial difference can be attributed to the reduced ischaemic times in
[28]
Z-2-FET achieved by LSA rerouting, as detailed elsewhere by this group . Others have also demonstrated
[40]
Z-2-FET renal failure/dialysis rates of 13.3%-14.5% compared to Z-3-FET rates of 17.7%-20.7% [8,29] .
Intriguingly, Panfilov et al. reported that renal replacement therapy was needed in 29.4% of Z-2-FET
patients vs. 25.9% of Z-3-FET patients (P = 0.833) . However, it must be noted that their sample size
[31]
(n = 17, Z-2-FET; n = 27, Z-3-FET) is appreciably smaller compared to the previously mentioned studies.