5.2 TEVAR with chimney stent
graft
This surgical approach has been shown to be reliable in cases where a
suitable proximal landing zone can be established, where a simple left
carotid to left subclavian bypass or one chimney stent graft for the
left subclavian in sufficient (Carino et al. , 2019). When the
aortic pathology involves or is in close proximity to the aortic
branches, it is paramount that the endografts must cross their ostia in
order to produce an adequate seal (Malina, Resch and Sonesson, 2008). In
this scenario, a standard angioplasty/stenting technique otherwise known
as a chimney graft can make performing a TEVAR procedure possible using
off the shelf devices (Greenberg et al. , 2003; Donas et
al. , 2010). This technique, first reported by Greenberg et al. and
subsequently described in detail by various other vascular groups, is a
means of gaining additional fixation length in order to stabilise the
aortic stent grafts whilst also safeguarding perfusion to the vital
branches (Greenberg et al. , 2003; Baldwin et al. , 2008;
Donas et al. , 2010; Criado, 2007). However, the addition of a
chimney stent graft has been shown to increase the risk of type IA
endoleak (Ahmad et al. , 2017).
A 2016 study by Huang et al. describes 27 consecutive non-A non-B
patient outcomes without adequate proximal landing zones that were
treated with the chimney stent graft endovascular technique with a mean
follow up time of 17.6 months (Huang et al. , 2016). Chimney
stents were deployed parallel to the main endografts in order to
preserve blood flow while extending the landing zones. The technical
success rate published was 100% with endografts deployed in zone 0 (3),
zone 1 (18) and zone 2 (6). Proximal endoleaks were reported in 5
patients immediately after surgery and were treated with kissing balloon
technique in order to minimise gutter formation. Computed tomography
angiography showed all aortic stent and chimney stent grafts to be
patent post-surgery. Huang et al. also report a 0% 30-day mortality
rate and a 0% retrograde type A dissection, however 2 out of the 27
patients were reported to have suffered a stroke post operatively (Huanget al. , 2016).
Zhu et al. has also previously reported similar results in terms of
success and also the incidence of endoleak whilst utilising this
technique in a cohort of 34 patients (Zhu et al. , 2013). The
technical success was reported at 82% and immediate type I endoleaks
were reported in 5 patients all of which underwent bare chimney stent
techniques (Zhu et al. , 2013). No perioperative death or strokes
were observed however one perioperative morbidity included an
ST-elevation myocardial infarction. The mean follow-up for this study
was 16.3 months and primary patency was maintained in all the chimney
stents as well as in the surgical bypasses across this period with no
incidence of stent fracture or chimney-related endoleak observed in
addition. The authors conclude that this technique provides a minimally
invasive way of the preservation of arch branch blood flow with
favourable mid-term outcomes. However, the study also concluded that the
application of the bare chimney stents seemed to be associated with a
higher incidence of immediate type I endoleaks and suggests that
balloon-expandable stents should be regarded as the first choice because
of their greater radial strength (Zhu et al. , 2013).
An earlier study by Shu et al. reported outcomes of the chimney
stent-graft technique on 8 patients treated for Non-a non-b aortic
dissections with no adequate proximal sealing zones (Shu et al. ,
2011). Covered stents were placed parallel to the aortic stent grafts in
order to restore flow to the left common carotid artery while extending
the proximal fixation zones; the left subclavian arteries were also
intentionally covered after cerebrovascular assessment. All 8 procedures
were completed successfully with one main aortic stent graft deployed
alongside one chimney graft implanted in the left common carotid artery.
The authors report two retrograde type II endoleaks that were identified
perioperatively but were left untreated but followed closely using
computed tomography (Shu et al. , 2011). They also report no
instances of any puncture site complication, strokes, death or paralysis
during the hospital stay and a 30-day mortality of 0%. Mean follow-up
was 11.4 months and during this time there was no mortality with duplex
ultrasound and computed tomography displaying patency of stent grafts,
enlargement of the true lumen and compression of the false lumen (Shuet al. , 2011). One of the type II endoleaks disappeared in two
weeks post-operatively while the other faded gradually until almost
disappearance at 11 months post-operatively.
A 2015 study by Liu et al. reported outcomes of 41 consecutive patients
treated with the chimney stent graft technique for Non-a non-b aortic
dissection including 8 emergent repairs (Liu et al. , 2015). This
technique was utilised to reconstruct the left subclavian artery in 5
patients and the left common carotid artery in 34 patients. In 2 cases
the double chimney technique was used in order to simultaneously
reconstruct the innominate artery and the left common carotid artery.
The mean follow-up period for this cohort was 17.3±6.1 months and the
authors reported a 0% 30-day mortality rate (Liu et al. , 2015).
None of the patients were reported to have a type I endoleak however
four had type II endoleak. During the follow-up no patients were
reported to have suffered severe neurological complications, migration
or occlusion of any stent grafts. Similar results including 0% 30-day
mortality, 0% stroke and 0% retrograde type A dissection were reported
in a study by Zou et al. while using the chimney stent graft technique
in a Non-A non-B dissection cohort (Zou et al. , 2016).