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).