Prosthesis implantation and rewarming
Following resection of the aortic arch, the FET stent graft is then
implanted and anastomosed. The guidewire preoperatively placed in the
thoracic aorta is used to aid anterograde introduction of the FET stent
graft which, when positioned, is anastomosed with the native aortic wall
and proximal arch graft at Zone 2, at the distal border of the left
subclavian artery.11, 13 Lower body perfusion is
initiated following distal stent to graft anastomosis, usually via a
4th branch in the arch graft in devices such as
Thoraflex, E-vita Hybrid Plus, and Frozenix J
Graft.11-13 Alternatively, in systems lacking a fourth
branch (such as E-vita Open), lower body perfusion is achieved via
insertion of a Foley catheter into the graft lumen.5In addition, Desai and colleagues also suggest combining TAR with a
thoracic endovascular aortic repair (TEVAR) graft anastomosed at Zone
2.21 A 2-branched Vascutek Gelweave arch graft is
implanted following aortotomy, and anastomosis of the left common
carotid and brachiocephalic trunk follows. The graft is proximally
anastomosed to an ascending aortic graft, and the TEVAR single-branched
stented endograft (GORE TBE) is then introduced via a guidewire
introduced at the femoral artery and externalised at the left brachial
artery. Stent positioning and rotational alignment is confirmed, and the
portal branch is secured in the root of the left
subclavian.21 Once proximal graft anastomosis is
completed, the arch vessels are reimplanted onto the arch graft.
Rewarming and reperfusion are then initiated.5
Graft implantation in Z-0-FET using the Frozenix J Graft and Thoraflex
systems, described by Yamamoto et al. and Jiang et al.respectively, is similar to Z-2-FET.16, 18 The FET is
advanced anterograde into the descending aorta following aortotomy, and
the distal end of the stent is positioned superior to level of the
aortic valve. The stent is then anastomosed to the four-branched
polyester graft and the native aortic wall at the distal zone 0 border,
and lower body perfusion is initiated via the fourth branch. Following
proximal anastomosis, the arch vessels are then reimplanted: the
brachiocephalic trunk and left carotid arteries are anastomosed to the
second and third graft branches respectively, and the left subclavian is
eventually anastomosed to the first branch. The fourth branch is ligated
(Figure 2).16, 18
An alternative approach to Z-0-FET, using the 3-zone (not to be confused
with zone 3) E-novia prosthesis, was first outlined by Jakob et
al. in May 2020 (Figure 3).17 This novel approach
deploys a single, continuous prosthesis divided into three zones: a
proximal polyester cuff used to secure the zone 0 anastomosis, an
uncovered stent portion to span the aortic arch, and finally a distal
covered stent (elephant trunk) portion positioned in the proximal
descending aorta.17 Following aortotomy and aortic
root repair, the resected proximal ascending aorta is replaced with a
regular tube graft. The 3-zone graft is then introduced anterograde
along the guidewire into the descending aorta and positioned such that
the proximal end of the elephant trunk portion is positioned just distal
to the origin of LSA. The non-covered stent portion is then manually
moulded to the curvature of the aortic arch and secured with a staying
suture. Finally, the proximal collar is trimmed and anastomosed to the
distal end of the ascending aortic prosthesis. Rewarming is then
initiated.17 Notably, the aortic arch is left
relatively untouched: the non-covered stent portion provides structural
integrity while facilitating blood flow out of the three arch vessels.
Proximalisation of the FET procedure from zone 3 to zone 2 has already
shown to provide improved surgical access and facilitate a more
straightforward surgical approach.1, 5 By bringing the
anastomosis forward into the surgical field, the surgeon is afforded
easier access to the aortic arch – it therefore stands to reason that
proximalisation from zone 2 to zone 0 would further amplify these
advantages and further simplify an already exceedingly complex
procedure.5 Indeed, the difficulty in accessing the
proximal DTA via midline sternotomy should not be understated. This
would have the added benefit of reducing overall surgical trauma,
overall duration of the procedure, and hence time spent under CPB, ACP,
and HCA – factors which are well-documented indicators of poor
postoperative prognosis.18 Indeed, Yamamoto et
al. and Jakob et al. highlight the mean CPB duration for Z-0-FET
as being 184 (±34) minutes and 176 (±39) minutes respectively, compared
to 262 (±84) minutes and 254 (±52) minutes reported for Z-2-FET by
Beckmann et al. and Jakob and colleagues.11, 12,
16, 17 Similarly, HCA duration for Z-0-FET is cited as being around 47
(±7) minutes, compared to up to 126 (±43) minutes for
Z-2-FET.11, 16 At this juncture, it is also worth
emphasising that anastomosis of the arch vessels to a trifurcated graft
in Z-0-FET (e.g., the Spielvogel device) is itself challenging, as is
the proximal graft-aorta anastomosis.20 Sinusoidal
orientation of the trifurcated graft, and supra-aortic stenosis at the
level of the graft take-off, are possible intraoperative complications
to be dealt with – perhaps these could be avoided by performing
proximal anastomosis at Zone 1.
Choudhury et al. outline the features, benefits, and drawbacks of
several key prosthetic systems available for aortic arch repair with
FET.5 Notably, the E-vita Hybrid Plus and Frozenix J
Graft prostheses both feature a two-stage non-stented graft and
stented-FET design, allowing deployment from either zone 2 or
0.16, 22 Further, the intussuscepted design of the
E-vita Hybrid Plus system also allows deployment from zones 3 and
4.23 Indeed, Harky et al. suggest that the
E-vita Hybrid Plus is associated with lower rates of postoperative
mortality than the Thoraflex device, which Jiang et al. concluded
constitutes a viable surgical bailout option when used in Z-0-FET
repairs.18, 24 These systems
therefore offer a more patient-centric approach, specific to the unique
anatomy and surgical context of each case and are perhaps best suited to
facilitating proximalisation of aortic arch repair.