5.4 Frozen elephant trunk

Another surgical treatment utilised in the surgical management of non-A non-B aortic dissection with proximal entry tear is the frozen elephant trunk technique (FET). This procedure involves ascending aorta and arch replacement in combination with antegrade stent graft implantation in the descending thoracic aorta while using a single hybrid prosthesis (Shrestha et al. , 2015). A recent systematic review and meta-analysis by Carino et al. found that 7% of patients were treated with this technique and that FET may also be an important option in cases of malperfusion syndrome as it can potentially open the compressed true lumen and cover any additional entry tears that could be positioned in the proximal descending aorta so that pressurisation the false lumen is maintained (Di Bartolomeo et al. , 2017; Shrestha et al. , 2015; Carino et al. , 2019). FET is also recognised in the literature to promote favourable remodelling in the distal aorta (Dohleet al. , 2016; Iafrancesco et al. , 2017). Another advantage of FET is no type I endoleak as well as its ability to establish a highly stable proximal landing zone for the eventual stent graft implantation in the descending thoracic aorta (Berger et al. , 2019; Berger et al. , 2018; Dohle et al. , 2016). However, the main limitation associated with FET is the increased surgical trauma secondary to the necessarily prolonged periods of extracorporeal circulation, circulatory arrest as well as myocardial ischemia (Carinoet al. , 2019). In addition, the technical demand of this procedure requires experienced surgeons in high volume aortic centres (Shrestha et al. , 2015).
A 2020 study by Kreibich et al. reports outcomes of the FET technique to treat 41 patients presenting with acute complicated or chronic type B or non-A non-B aortic dissection (Kreibich et al. , 2020). FET was implemented when supra-aortic vessel transposition would not suffice to create a satisfactory proximal landing zone for TEVAR, when a concomitant ascending or arch aneurysm was present or if any patients suffered with any connective tissue disorders. Of these 41 patients, 23 presented with a non-A non-B dissection (Kreibich et al. , 2020). In the 41-patient overall cohort one patient was reported to have died intra-operatively secondary to an aortic rupture in downstream aortic segments however no other post-operative deaths occurred. 4 patients suffered a non-disabling stroke post-operatively and were subsequently discharged with no clinical symptoms (1 patient), no significant disability (2 patients) or with slight disability (1 patient) (Kreibichet al. , 2020). The authors report one patient death during follow-up after two years (not aorta related) and 16 patients subsequently underwent an aortic re-intervention after 7.7 months (Kreibich et al. , 2020). Kreibich et al. concluded that FET is an effective treatment option for acute complicated and chronic type B as well as non-A non-B aortic dissection patients in whom primary endovascular was not deemed as feasible. They also conclude that this study underlines the considerable need for aortic re-interventions and the importance of continuous follow-up of patient after undergoing FET procedures (Kreibich et al. , 2020).
An earlier study by Zhao et al. assessed 24 consecutive patients with non-A non-B aortic dissection treated with the FET technique (Zhaoet al. , 2012). This cohort also included concomitant procedures including the Bentall procedure in 3 patients, David procedure in 1 patient and ascending aortic replacement in 7 patients (Zhao et al. , 2012). The in-hospital mortality rate was recorded at 4.1% with one patient dying of multi-organ failure after surgery (Zhao et al. , 2012). No incidences of paraplegia were reported (Zhao et al. , 2012). During follow-up one patient was reported to have died following gastrointestinal bleeding 2 months after surgery and type II endoleak occurred in 1 patient. The 5-year survival rate was 91.7% (Zhao et al. , 2012). The authors concluded that the application of this technique was safe and feasible for non-A non-B aortic dissection with a low rate of mortality and morbidity as well as a satisfactory 5-year survival rate (Zhao et al. , 2012).
A 2016 study by Urbanski et al. surgically treated 8 patients with a non-A non-B aortic dissection, with 4 patients treated surgically and 4 patients conservatively (Urbanski and Wagner, 2016).
Amongst the surgically treated patients, 1 patient underwent a partial arch replacement, and the remaining patients received a complete arch replacement via a modified elephant trunk technique (Urbanski and Wagner, 2016; Urbanski et al. , 2010). In the surgically treated cohort, there were no reported deaths or relevant clinical events recorded during a median follow-up time of 40 months (Urbanski and Wagner, 2016). In the conservatively treated patient group, 3 patients had died by 28 months of follow-up, 1 from an aortic rupture and 2 due to the progression of the dissection and subsequent malperfusion (Urbanski and Wagner, 2016). The authors concluded that surgical treatment of acute aortic dissection involving the arch but sparing the ascending aorta seemed to offer improved clinical outcomes (Urbanski and Wagner, 2016).