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Page 8 of 12 Geragotellis et al. Vessel Plus 2023;7:6 https://dx.doi.org/10.20517/2574-1209.2022.41

Haemostasis
Evidence in the literature suggests that Z-2-FET is associated with lower rates of bleeding requiring re-
intervention compared to Z-3-FET. Longer CPB times, and associated physiological derangements,
[41]
associated with Z-3-FET in the foreground of multiple vascular anastomoses offer a possible explanation .
To elaborate, Detter et al. found that 3.3% of the Z-2-FET group required re-sternotomy for bleeding/
[29]
tamponade in comparison to 17.7% of their Z-3-FET group . Similarly, Panfilov et al. achieved a 0% re-
intervention rate for bleeding using Z-2-FET vs. 11.1% using Z-3-FET .
[31]
Aortic remodelling and FL thrombosis
Aortic remodelling refers to the process by which the aortic lumen returns to normality through expansion
of the true lumen and regression of the FL through FL thrombosis. In their recent review, Jubouri et al. and
[4,6]
Kayali et al. showcased the excellent aortic remodelling associated with FET . Panfilov et al. is the only
identified study directly comparing aortic remodelling achieved with Z-2-FET and Z-3-FET head-to-
head . The aorta was divided into three segments during follow-up radiological imaging to assess and
[31]
compare remodelling. Segment A was the length along the FET HP; segment B was from the distal end of
the stent graft down to the coeliac artery level; segment C was from the coeliac artery to the aortic
bifurcation level. Figure 2 (reproduced from Panfilov et al.) represents the overall results . The authors
[31]
concluded that Z-3-FET is associated with improved aortic remodelling and FL thrombosis in the long
term. This finding can be attributed to the extended coverage of the DTA distally by the FET stent graft in
Z-3-FET .
[31]

ZONE 0 FROZEN ELEPHANT TRUNK
Recently, FET practice has shifted towards the proximalisation of the distal device anastomosis (or proximal
landing zone of the stent graft) at Zone 0 of the aortic arch. The literature has hinted at this technique’s
superiority over Z-2-FET regarding operative times and clinical outcomes . The Z-0-FET can be performed
[7]
using two main surgical techniques. The first is the hybrid arch repair, which requires debranching of the
supra-aortic vessels, an example of which is illustrated in Figure 3 [42,43] . The second uses FET HPs that
facilitate Z-0-FET without time-consuming supra-aortic vessel debranching [44,45] .

Yamamoto et al. presented their single-centre experience with Z-0-FET in 108 patients . The 30-day and
[42]
in-hospital mortality rates were 2.8% and 6.5%, respectively, with overall survival at 1, 2, and 3 years being
89.8%, 88.1%, and 88.1%, respectively. As for neurological outcomes, new-onset permanent neurological
[42]
dysfunction and SCI occurred in 3.7% and 0% of patients, respectively .
Tan et al. recently published a literature review comparing Z-0-FET with Z-2-FET . Using data from
[7]
independent studies, the authors highlighted several clinical outcomes, including aortic remodelling,
mortality, neurological injury, renal injury, RLN injury and re-intervention. Overall, Z-0-FET can be
considered a superior solution for complex thoracic aortic disease, offering optimised results compared to
Z-2-FET, except for aortic remodelling and FL thrombosis. This improvement in clinical outcomes can be
attributed to the reduced operative times, including CPB duration, due to the more straightforward surgical
access and the increased exposure of the anastomosis site. On the other hand, the decreased coverage of the
DTA distally with Z-0-FET can explain the inferior aortic remodelling and FL thrombosis observed .
[7]

A solid conclusion on Z-0-FET’s superiority cannot be drawn at this stage since it is still relatively novel. In
addition, Z-0-FET is not yet as well-established within the literature as Z-2-FET and Z-3-FET. Therefore,
more studies investigating this potential paradigm-shifting technique are needed to reach a definitive
consensus.