Corresponding Author:
Prof Mohamad Bashir MD PhD MRCS1
Vascular & Endovascular Surgery
Velindre University NHS Trust
Health Education & Improvement Wales
Nantgarw, Wales, CF15 7QQ
United Kingdom
Drmobashir@outlook.com
Funding: None
Conflicts of Interest: None
Keywords: Frozen elephant trunk, aortic arch; aortic
dissection; aortic aneurysm, vascular prosthesis, Thoracoabdominal
aortic aneurysm
In the current era, thoracic aortic disease management is tailored to
patients’ associated comorbidities, risk profile, surgeon’s skills, and
expectations. Consequently, focused surgical approaches are mandated to
facilitate intervention which would impact outcomes and survivability.
Although the conventional 2-stage elephant trunk technique alleviated
distal thoracic aortic management, its applicability was limited by the
failure to complete the repair (1). The advent of frozen elephant trunk
(FET) ameliorated those shortcomings allowing a single-stage repair of
extensive aortic arch disease or facilitating a staged thoracic
endovascular aortic repair (TEVAR) of extensive aortic disease (1). Its
advantage is that the stented graft, unlike a conventional elephant
trunk prosthesis, can be securely anchored at the desired level distally
in the descending thoracic aorta (1). Interventions on distal aortic
pathologies via TEVAR or endovascular aneurysm repair (EVAR) also
facilitate the manage thoracoabdominal aortic aneurysms. Such an
approach for aortic repair is often taken, for example in cases of
DeBakey type I aortic dissection (2).
Hybrid aortic surgery means that the entire thoracic and abdominal aorta
can be repaired limiting often poor outcomes seen in open surgery.
Conventional thoracic aortic surgery evolved, and FET established a
platform for dealing with distal aortic pathology by providing an
excellent landing zone. The growing evidence in the literature balanced
on observational data around the use of FET meant that distal aortic
disease shifted to a rather repairable segment through TEVAR, especially
in acute settings. This is also applicable to patients with retrograde
type A aortic dissection with a primary entry tear in the descending
thoracic aorta. This strategy eliminated the necessity for second stage
open aortic repair (3). Indeed, Berger et al. have demonstrated that the
FET technique was associated with up to 95% positive remodeling around
the perigraft space, which translated therefore to a lower risk of
reintervention: bolstering the versatility of the FET technique (4).
Furthermore, in patients with multilevel thoracic aortic pathology, when
the threshold for intervention has not yet been reached, this strategy
enables endovascular completion to be performed. The therapeutic
versatility offered by FET has undoubtedly been key to its widespread
adoption in the management of aortic arch disease, and this strategic
advantage is central to providing personalized aortic care. The adoption
of evidence-based guidelines for prosthesis sizing (discrepancy in FET
sizing practices is a well-known issue within the aortovascular
community), together with the development of custom-made grafts for
elective repair, would undoubtedly augment hybrid repair of complex,
multisegmented aortic disease.
In cases necessitating multi-stage repair of the aortic arch and
thoracoabdominal segments, it is vital to consider the downstream
effects of proximal repair in contributing to the management of distal
aortic pathologies. Berger et al. noted that in addition to extensive
positive remodeling around the perigraft space, false lumen thrombosis
was observed around the coeliac trunk in 37% of patients, 12 months
post-implantation (4). As such, hybrid aortic interventions mitigate the
trauma of a complete thoracoabdominal open approach, harness the
downstream beneficial effects of proximal repair, and use innovative
graft design (such as branched EVAR) to remove the need for open
revascularisation. Post-FET thoracoabdominal stent-grafting therefore
allows a safer alternative to extensive aortic repair in the high-risk
patient population (2, 4).
Clamping of the stent-graft in the open thoracoabdominal approach
following FET is not without concerning complications. Although due to
its self-expanding capability and associated memory effect nitinol can
retain its original anatomical configuration, fracture and hematoma
following stent-graft clamping has been reported (5). Kreibich et al.
report an incidence of stent leakage during second-stage
thoracoabdominal aortic repair wherein clamping of the stent lead to
leakage around the proximal graft. It is suggested that the authors’
unfolding of the folded stent led to compromise of the newly formed
neo-intima and neo-adventitia, disrupting tissue formation, and causing
leakage (5). Additionally, an anastomosis between the distal end of the
stent-graft and a conventional Dacron prosthesis in an open approach has
its limitations (3). Proof-of-concept small studies highlighting a
second-stage open replacement after previous FET implantation are biased
with a low sample and colliding nature. The challenge of navigating the
abdominal visceral arteries can be overcome with coverage of the false
lumen origin with a covered endovascular stent-graft and subsequent use
of the PETTICOAT technique (6). This involves deploying a bare-metal
stent with low radial force distal to the covered stent-graft into the t
abdominal true lumen (6). Such techniques amongst others have all been
added to the armamentarium of endovascular intervention for extensive
aortic disease, providing an alternative to invasive open repair
post-FET implantation, negating the need for clamping of the FET
stent-graft. These interventional approaches are always advised to be
undertaken in high-volume aortic centers with a team approach using
protocols dedicated to spinal cord ischemia prevention.
Hybrid or staged approaches for thoracoabdominal aortic aneurysm after
FET have far proven effectiveness in the mid and long-term, and are
recommended in cases where TAAA are involved alongside aortic arch
pathology (7).