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.