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Page 2 of 12 Geragotellis et al. Vessel Plus 2023;7:6 https://dx.doi.org/10.20517/2574-1209.2022.41

reach a definitive consensus on the most optimal FET technique. The present literature review aims to provide an
overview of major intraoperative and postoperative outcomes achieved with Z-2-FET and Z-3-FET and summarise
evidence from studies directly comparing them. Another aim of this narrative review is to explore current literature
trends on Z-0-FET uptake.

Keywords: Thoracic aortic disease, aortic dissection, aortic aneurysm, aortic arch zones, frozen elephant trunk
(FET), total arch replacement

INTRODUCTION
Total arch replacement (TAR) via frozen elephant trunk (FET) is a strategy for managing complex thoracic
aortic pathologies involving the arch and descending thoracic aorta (DTA). Since its introduction, FET has
revolutionised the field of aortovascular surgery by achieving superior results to conventional arch repair
techniques, leading to its continuously increasing uptake. FET hybridises an “open-repair” approach with
endovascular techniques. The stented ‘frozen’ distal elephant trunk segment, introduced into the DTA, also
allows for a single-stage procedure. The FET surgical technique involves anastomosis of the distal cuff of the
[1,2]
FET hybrid prosthesis (HP) to the native DTA wall at a chosen aortic arch zone . The aortic arch zones
are defined according to anatomical classifications established by Mitchell and Ishimaru [Figure 1].
[3]
Though the distal anastomosis was traditionally performed at Zone 3 (Z-3-FET) of the aortic arch, there is
debate on whether adopting Zone 2 (Z-2-FET) implantation improves surgical access and clinical
[1,2]
outcomes . As illustrated in Figure 1, Zone 2 involves the aortic arch between the left common carotid
artery (LCCA) and the left subclavian artery (LSA), while Zone 3 involves the proximal DTA distal to the
LSA. It is also possible that the re-intervention rates secondary to a new distal stent graft-induced entry tear,
aortic dilatation, and endoleak will decline when the most appropriate FET HP type, size and length are
[4-6]
used with a more proximalised distal anastomosis site . Nevertheless, it is essential to note that clinical
outcomes with Z-2-FET and Z-3-FET can be influenced by the complexity and severity of the underlying
pathology and the surgical technique adopted for supra-aortic vessel re-implantation, intraoperative
perfusion, and cerebral protection. There is additional debate on whether proximalisaton of the distal
anastomosis to Zone 0 of the arch will optimise outcomes . The current literature review aims to provide
[7]
an overview of major intraoperative and postoperative clinical outcomes of Z-2-FET and Z-3-FET, with a
focus on studies that explicitly compare results of Z-2-FET and Z-3-FET head-to-head, including operative
times, mortality, neurological complications, recurrent laryngeal nerve injury, respiratory and renal
outcomes, haemostasis, and aortic remodelling. Another scope of this review is to explore current literature
trends in the uptake of Zone 0 FET (Z-0-FET).

ZONE 2 FROZEN ELEPHANT TRUNK
Z-2-FET technicalities
Z-2-FET implantation involves resection of the diseased aortic arch up to the area distal to the LCCA but
proximal to the origin of the LSA. Following resection and inspection of the remaining distal arch and DTA,
the stent graft can be introduced over the femoral guide wire (if used) into the true lumen and anastomosed,
with caution to ensure residual LSA patency. As aforementioned, emerging evidence over the past decade
has supported this “proximalised” approach to TAR with FET: beyond Zone 2, the distal arch and DTA sit
relatively deep and posterior within the chest cavity, making distal resection, inspection, and anastomosis
more challenging . Zone 2 implantation is, therefore, likely to involve decreased visceral circulatory arrest
[1,8]
and cardiopulmonary bypass (CPB) durations, which are changes that may reflect improved clinical
outcomes. Various Z-2-FET techniques for supra-aortic vessel implantation and LSA revascularisation exist,
the choice of which can influence results.