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Embolic Materials andEmbolization
https://t.me/medicina_free
Techniques
ElenaLucertini andMiltiadisKrokidisAthens
14
Case Presentation
Case Background
A chest CT scan of a 49-year-old female performed for
other reasons revealed as incidental nding the presence
of an arteriovenous communication between the right pulmonary artery and the right pulmonary vein. When the
patient was asked, she recalled two previous episodes of
transient cerebral ischemic events in the last 10years with
negative cerebral CT scans. She also referred to suffering
from regular nosebleeds since her adolescence and that
her mother and her younger sister also suffer from regular
nosebleeds. The diagnosis of hereditary haemorrhagic telangiectasia (otherwise known as Osler-Weber-Rendu disease) was made and a decision to proceed with
embolization of the pulmonary arteriovenous malformation (AVM) followed.
Background
Transcatheter arterial embolization is one of the major applications of endovascular embolization and it is dened as the
deliberate occlusion of arterial vessels for the treatment of
diseased or injured vasculature.
Arterial embolization has been used since the beginning
of the twentieth century, initially with the aim of reducing
tumour blood ow before surgery in hypervascular tumours
and afterwards also to treat arteriovenous malformation
(AVM) and arteriovenous stulas (AVF) [1, 2].
At present, endovascular embolization has been extended
to multiple clinical areas in both emergency and nonemergency settings. In an emergency, embolization is performed to stop active bleeding from an arterial source, due
to trauma, ruptured aneurysm, or even due to diffuse anti-
coagulation [3–7]. In an elective setting, transcatheter
embolization is used to seal non-ruptured aneurysms, and
to treat AVMs and endoleaks after endovascular repair of
abdominal aortic aneurysms [5–11]. Furthermore, embolization has offered minimally invasive oncologic solutions
for the treatment of hepatocellular carcinoma (HCC) or
liver metastatic disease but also revolutionized the approach
to benign pathologies like broids and prostate hyperplasia
that can now be treated without surgical interventions
[12–15].
Indications forIntervention
The main indication for the treatment of embolization is
the necessity of selective occlusion of a very specic vascular area or the delivery of drugs via an intra-arterial
route in a designated anatomical area or organ. Patients
may have a very good general status for an elective procedure or equally may be severely unwell when embolization procedures are performed with a life-saving purpose,
e.g., bleeding after pelvic trauma or postpartum. In an
elective setting it is preferred to avoid performing embolization in patients with a bleeding risk and to postpone the
procedure until their status is optimized. Nevertheless,
embolization in emergency may be performed even in
patients with deranged clotting with the use of appropriate
tools, e.g., closure devices for the arterial closure and
embolic materials that do not depend on clotting function,
like glue.
Preoperative Preparation
Timing ofIntervention
E. Lucertini
Ospedali Riuniti di Livorno, Livorno, Italy
M. K. Athens (*)
National and Kapodistrian University of Athens, Athens, Greece
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
G. Geroulakos et al. (eds.), Mastering Endovascular Techniques, https://doi.org/10.1007/978-3-031-42735-0_14
Embolization may be performed as an elective or as an emergency procedure. A 24-h embolization service is required to
be available at all tertiary care surgical and trauma centres,
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E. Lucertini and M. K. Athens
and in case bleeding from an arterial source is documented,
the procedure is expected to take place within 30–60 min
while the patient is resuscitated.
Anticoagulation
The coagulation status of the patient needs to be assessed prior
to an embolization procedure to select appropriate materials.
This is usually performed by asking about the intake of any anticoagulation drugs (e.g. heparin, clopidogrel) and if or when they
have been stopped and by performing the required blood tests
(e.g. INR, platelet count) prior to the procedure.
Imaging
The procedure is performed under digital subtraction
angiography (DSA). However, adequate imaging prior to
the procedure is required for planning. Computed tomography (CT) angiography is usually used for that purpose.
Pictures need to be obtained in arterial phase after bolus
tracking of intravenous contrast material. Use of
Maximum Intensity Projection (MIP) reconstruction may
be helpful particularly when embolization of small vessels is required (e.g. gastrointestinal bleeding). In some
cases, magnetic resonance (MR) angiography may be
used instead of CT in combination with the imaging of the
organ that required embolization (e.g. MR imaging of
uterine broids prior to treatment). Intraoperative imaging with cone bean CT may also be required to conrm
embolization target (e.g. prostate embolization).
Materials andTechniques
Endovascular access is obtained, and a standard endovascular kit is used in most cases that consists of the following:
• Standard access wires and sheaths (ranging from 4 to
12Fr).
• Selective 4 or 5Fr catheters.
• 0.035″ hydrophilic guidewire
• 0.027″– 0.021″ microcatheters
• 0.021″– 0.010″ microwires
• Embolization material.
The rst embolization materials used historically were
blood clots, small muscle fragments and stainless-steel pellets [16]. Recently, with the advancement of medical technology, a wide range of embolic agents have been developed,
and adequate knowledge of the different types and features is
mandatory for embolization specialists.
Mechanical Embolic Agents
Coils
Coils are one of the rst embolic agents used; they aim to
mechanically occlude vessels or aneurysms. The rst
embolic coils were made from small pieces of Teon guidewires that were cut after removal of the inner core; they were
introduced in 1976 by Gianturco and named after him [17].
The rst generation of coils were developed as separate
devices, with thrombogenic coating, but none of them could
be retrieved after deployment and were therefore named as
“pushable” coils [18]. Coils that could be retracted after
deployment within an electrolytic mechanism – therefore
“retrievable”– were developed in 1989 by Guglielmi, allowing repositioning in case of suboptimal positioning or size.
Controlled detaching of coils was a real revolution in embolization techniques. After Guglielmi, many other detachable
coils were developed, using electrolytic or mechanical
detaching systems [5].
Apart from the type of deployment system other features
also distinguish coils and in particular size, shape, exibility
and bioactivity. All coils are developed for long-term implantation and are therefore made of bio-inert materials, to avoid
local or systemic adverse responses. The most common
material for coils is platinum, but nitinol has also been
recently introduced. Platinum is a radiopaque, highly thrombogenic, very exible and compliant material, allowing a
good packing density with low trauma risk on vessel or aneurysm wall and permitting an optimal conformation into the
shapes of irregular aneurysms [19]. Nitinol on the other hand
is more of a shape-memory material, mainly used in stent
production; it is very exible and offers higher radial force
compared to platinum [20].
In addition to the traditional bio-inert bare metallic coils,
hydro coils, bioactive coils and polymer- or protein-coated
coils have been produced. Bioactive and coated coils were
developed with the aim of increasing their thrombogenic
effects, consequently obtaining faster occlusion of aneurysms or vessels, while hydrocoils are coated by a hydrogel
layer in order to improve packing density and obtain larger
lling volumes [21].
Plugs
Plugs are mechanical occlusion devices produced with
shape-memory polymers specically designed to occlude
vessels quickly with a single re-sheathable device. Plugs
determine mechanical obliteration of vessels and consequent deceleration of blood ow, nally causing thrombosis
[16, 22].
Stents andFlow Diverters
Stents play a very important role in embolization procedures
as they are not only able to reconstitute the wall of a dam-
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131
aged or aneurismatic vessel, but they can also be of help in
other widespread embolization techniques such as coiling
using a “stent-assisted coiling” technique. Stents nd their
greatest use in the treatment of bleeding caused by damage
to a main arterial or venous vessel, which cannot be completely occluded without causing potential distal organ ischemia, and in the embolization of both visceral and cerebral
aneurysms.
In the rst case, covered-mesh stents are commonly used
to reconstitute the wall of the damaged vessel, stopping the
bleeding and ensuring the maintenance of the blood ow
through the treated artery or vein. Necessary conditions for
this type of procedure are to have adequate distal and
proximal stent landing zones, without excessive size discrepancy of the proximal and distal landing areas, not to have
signicant tortuosity of the parent vessel, and to guarantee
that the placement of the covered stent does not lead to
occlusion of some essential vascular branch, for example
when the damage is located close to an arterial bifurcation
[23–25].
Another device similar to stents are the ow-diverter
devices (FDDs), which can be placed in the artery covering
the aneurysm neck. The wall of FDDs blocks the blood ow
where it is turbulence, i.e. into the aneurismatic sac, but
maintains ow in the main vessel lumen. FDDs can be used
alone or in addition to coiling, depending on the case [26,
27]. They were initially introduced to treat cerebral aneu-
rysms, but their use has been extended to the treatment of
visceral aneurysms. However, there is no long-term information about their effectiveness in dealing with such large visceral aneurysms, especially in terms of ow-diverting power
[28, 29].
The “stent-assisted coiling” technique is particularly useful for wide-necked aneurysms with potential high risk of
coils displacement into the parent vessel. In this case, noncovered stents or FDDs may be used, depending on the case,
particularly if side branches that need to be preserved are
present. Coils can be placed after stent deployment by passing through the stent mesh with a microcatheter or with a
second microcatheter parallel to the one used to deliver the
stent, previously “jailed” between stent and artery wall into
the aneurysmatic sac, with the so-called jailing technique
[23, 25].
Detachable Balloons
Detachable balloons were initially used for endovascular
aneurysm treatment, but they soon were phased out.
Nevertheless, they are still used for the embolization of traumatic or congenital single-hole stulas.
Although their use alone is rather limited, balloons still
represent a good support for other embolization techniques.
In aneurysms embolization, the use of a temporary balloon
protection across the aneurysm neck considerably facilitates
its lling with spirals or plugs, avoiding at the same time
their escape from the sac during the procedure. Another
application of balloons in embolization techniques is in neurovascular procedures, where balloons may be used to
occlude the ow distally to the aneurysm, to prevent clot
migration during the procedure. In some cases, however,
even temporary arterial occlusion obtained with a balloon
may lead to the exclusion and thrombosis of a pseudoaneurysm sac [16, 30].
Particulate Embolic Agents
Particulate embolic agents are very commonly used in clinical practice. They include irregularly shaped or calibrated
particles, which can be natural or synthetic and permanent or
biodegradable. Particulates can be spherical such as microspheres or non-spherical such as polyvinyl alcohol (PVA)
and they are available in a number of sizes from 40 to
1200μm [16, 22].
Polyvynil Alcohol (PVA) Particulates
PVA particulates are commonly used for embolization, especially for uterine broids, hyperplastic prostatic gland and
hypervascular tumours. PVA are prepared by mechanical
fragmentation by rasping and blending or punching PVA
plugs out of the compressed foam, followed by sieving to
separate particles with different size ranges, between 100μm
and 1100 μm. Despite sieving, PVA are considered noncalibrated because of their irregular shape, which can promote aggregation, and because of the possible passage of
elongated particles through the sieves along their long axis
during the sieving process, resulting in some variability in
particles size. At the end of the process, PVA particulates are
a dry powder which needs to be hydrated with saline solution
and contrast medium before use.
After being delivered through a catheter, PVA particulates
determine immediate mechanical occlusion of blood vessels,
initially by attaching to the vessel wall and then, within the
rst few hours or days, by thrombus formation and nally by
inammation-induced vessel remodelling, wall necrosis and
brosis, determining a permanent vessel occlusion. However,
in some cases recanalization may occur. In such cases,
repeated embolization with PVA of the same vascular territory is still possible.
The biggest disadvantage of PVA is their high aggregation, due to the wide range of sizes within the particle group
and due to their irregular and hydrophobic surface, which
can cause blockage within the catheter or in the more proximal vessels (it is important to consider that the dimension of
particles does not necessarily correlate with the diameter of
occluded arteries); hence sometimes it is difcult to predict
the embolization behaviour [14, 31].
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Calibrated Microspheres
Microspheres, unlike PVA particles, are symmetrical and
very precisely sized (ranging from 40 to 1200μm) with a
smooth surface that reduces the risk of particle aggregation
and allows a more precise, size-dependent and predictable
embolization. Nevertheless, special attention needs to be
paid to potential particle reux and risk of non-target embolization during injection. The mechanism of embolization
with microspheres is similar to PVA particles, blocking the
ow into the vessel and inducing inammation and brosis,
though the induced inammatory reaction is lower with
microspheres compared to PVA. Embolization performed
with microspheres is considered permanent; however, reembolization may be possible if required.
In addition to size, further features to consider are rigidity
and elastic recovery, which respectively indicate the resistance to compression and the time required for the microsphere to regain its original shape.
Microspheres are available in prelled syringes, which
need to be diluted with uid (usually saline solution) and
contrast medium before injection. Depending on their use,
sizing of microspheres varies; for uterine broids embolization with larger microspheres is often performed (usually up
to 500–700 μm), while in tumour embolization, smaller
(100–150μm) microparticles are usually preferred to obtain
a deeper and more distal microvascular embolization.
Moreover, for oncologic treatment, various chemotherapeutic drugs may be encapsulated into designated microspheres
to enhance their therapeutic effect [13].
There are several types of microparticles available produced by different medical device companies. The rst
microspheres were introduced by Biosphere Medical and
they were the trisacryl gelatin (TAGM) microparticles named
Embosphere, available in a range of sizes from 40 to
1200μm. After them, many other microspheres were introduced by Biosphere Medical itself (EmboGold,
Quadrasphere, Hepasphere), Boston Scientic (Contour SE,
Bead Block, DC Bead) and CeloNova BioSciences
(Embozene). The different types of Embosphere differ in
rigidity, viscoelasticity, elastic recovery, level of occlusion
and generated inammation. Contour SE are the most occlusive particles, with lower rigidity, viscoelasticity and elastic
recovery, while Embosphere have the highest rigidity and
elastic recovery and the lowest level of occlusion. No signicant differences are reported in inammation level for particles with size >500μm, which is lower compared to smaller
spheres. In microspheres <500 μm, however, Embosphere
are those with the higher inammatory power [14, 31, 32].
Autologous Clots andTissues
Blood clots are the most commonly used temporary autologous embolic agents, including natural clots, which are temporary embolic agents, or modied clots. Clots can be heated
to retard the lysis or acidied in order to resist brinolysis.
Oxidized cellulose-modied blood or thrombin-modied
blood can also be used, as well as aged blood, possibly with
tantalum powder to make it radiopaque. Autologous tissues
include muscle and subcutaneous tissues, directly taken from
patients before the procedure and then cut into small pieces
and suspended into saline solution. Unlike blood clots, autologous tissues are considered permanent embolic agents.
Autologous embolic agents, especially blood clots, are cheap
and highly biocompatible; however, they are rarely used in
clinical practice, reserved for those rare cases in which a
rapid lysis of the clot to restore circulation within hours is
desired [16, 22].
Gelatin Foam
Gelatin foams are biodegradable embolic agents, very useful
for temporary embolization. They may be used as haemostatic embolic agents, for example for pre-operative embolization or for younger patients where permanent embolics
may not be the most preferable option. They mechanically
produce vessel obstruction and thrombus formation with a
similar mechanism to that of brin, causing haemostasis.
Gelatin embolics are available in different congurations
such as sponge or sheets, which can be manually cut into
smaller pieces up to 1–2 mm and then diluted with saline
solution and iodinated contrast to make them radiopaque.
They can be used in both endovascular and extravascular
procedures. When placed in soft tissues, gelatin foam usually
biodegrades completely within 4–6weeks [16, 22].
Liquid Embolic Agents
Liquid embolic materials allow homogeneous and complete
lling of the target vessels, reducing the risk of recanalization of the embolized area compared to mechanical and particulate embolics. On the other hand, liquid embolic agents
are considered slightly more challenging to handle and the
learning curve is somewhat steeper. They are preferably used
for the treatment of AVMs, AVFs and type II endoleaks and
they are increasingly used for bleeding control. Potential
risks like retrograde embolization, entrapment of the microcatheter tip and venous embolization need to be considered
[9, 30, 33].
Cyanoacrylates
After the replacement of isobutyl cyanoacrylate because of
suspected carcinogenesis, n-butyl cyanoacrylate (NBCA),
commonly known as “Glue”, became one of the most used
embolic agents in neurovascular interventions [34]. NBCA is
in uid state at the temperature of the room, and it polymerizes
almost immediately upon contact with ionic uids such as
blood or saline solution, but also heparin. This feature makes
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NBCA an excellent embolic agent; however, attention should
be paid to avoid early polymerization. Recommended injection rate is slow but continuous, to permit the glue to reach
with the ow the most distal part of the vessel or the nidus of
an AVM before it polymerizes; if NBCA is deposited too
proximally to the arterial feeder, the risk of recanalization is
high.
NBCA can also be mixed with other agents such as
Lipiodol in various concentrations but most commonly 1:3
or 1:4. This mixture modies the polymerization time.
Mixture of glue with metals like tantalum or tungsten powder offers higher radiopacity [9, 30].
The most commonly used cyanoacrylates are Histoacryl
(widely used for years for the embolization of cerebral AVMs
and dural AVFs with good results, although it has not yet
been approved for intravascular use), Glubran 2 (GEM SRL,
Viareggio, Italy), composed by a combination of NBCA and
metacryloxysulpholane to increase the polymerization time
and at the same time reduce inammatory and cytotoxic
effects, and Purell (Balt, Montmorency, France), composed
by n-hexyl cyanoacrylate with a very low adhesive power,
allowing longer injection time [35, 36].
Copolymers
Copolymers are non-adhesive liquid embolic agents
widely used in neuro-interventional procedures such as
AVMs or dural stulas embolization, but recently increasingly also in “peripheral” embolization. Copolymers are
always combined with dimethyl sulfoxide (DMSO),
which prevents their premature precipitation. Most commonly used copolymers are ethylene vinyl alcohol
(EVOH) based, and these produce occlusion of vessels by
precipitation, a mechanism described as similar to hardening of lava ow, and then solidify though the dissipation of DMSO [9].
Copolymers should be slowly injected over several minutes to create a proximal plug to facilitate anterograde
embolization and minimize backow. Sometimes, considerably long waiting periods may elapse between injections,
disrupting the progression of the embolic agent and forcing
the operator to prematurely abort the procedure. The innovative “pressure cooker technique” was introduced by
Chapot etal. to enable a comprehensive, forceful and continuous injection of Onyx and avoid reux, by creating a
plug of coils and glue between the tip and the detachment
zone of a previously placed microcatheter. The application
of this technique was then extended to all the other copolymers [9, 33, 37].
Compared to adhesive embolics like cyanoacylates, nonadhesive embolic agents have a signicantly lower risk of
trapping the microcatheter’s tip in the glue with consequent
inability to retrieve it. This phenomenon may still occur with
copolymers, but only when the reux of embolic material
has exceeded a certain distance from the tip of the microcatheter. To overcome this problem, some microcatheters with
detachable tips have been produced. Moreover, copolymers
precipitate within a longer period compared to the polymerizing time of cyanoacrylates, allowing for longer injection
times, more controlled embolization, and subsequent better
lling of the target vessel.
Before the injection of copolymers, the dead space of
the microcatheter must always be lled with DMSO, in
order to prevent precipitation of the agent within the microcatheter lumen. As DMSO can damage the material of the
catheter, DMSO-resistant catheters and syringes have been
developed and are recommended as the rst choice in such
cases.
There are four currently available copolymers: Onyx
(Medtronic, Irvine, CA, USA), Menox (Meril Life Sciences,
India Pvt. Ltd), Squid (Balt, Montmorency, France); and
PHIL (MicroVention, Aliso Viejo, CA, USA. Onyx, Menox
and Squid are all EVOH copolymers made radiopaque with
tantalum suspension, while PHIL is a different type of copolymer. The embolic material choice is based on the operator’s preference, availability, and level of expertise with each
agent, as well as the characteristics of the target lesion [9,
38].
Anticipated Complications
Post-embolization syndrome is the most common complication after particle embolization of a large area of the
body (e.g. broids, HCC). This consists of a u-like syndrome with fatigue and low temperature fever that is usually self- limiting and lasts approximately a week. In case
fever persists for longer, abscess formation of the organ of
the embolized area should be considered. In such cases,
cross- sectional imaging is required to conrm abscess
formation and treatment with intravenous antibiotics or
percutaneous abscess drainage may even be required.
Another possible complication is non-target embolization. This might lead to a series of undesirable outcomes
(e.g. bowel ischemia, skin ulceration) and should be
avoided by all means. With the use of liquid embolics
there is always the risk of catheter entrapment in the
embolized area. In such cases, the catheter needs to be left
in situ in some vascular territories, whereas in some cases
a surgical approach may be required.
Perioperative Care andSurveillance
After embolization the patient needs to follow the rules of
the vascular access that was used. The sheath diameter
and the use or not of closure devices will determine the
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E. Lucertini and M. K. Athens
hours that the patient would stay in bed. However, if radial
or brachial access is used the patient may be immediately
mobilized. The patient may also be mobilized after 2h in
case of procedures with venous access. In some cases, a
very strict antalgic regimen may be required post procedure (e.g. in the case of broid embolization a patientcontrolled anaesthesia pump is required). The patient is
usually discharged the next day for most elective embolization procedures; however, this is subject to the severity
of his condition. Follow-up visits are usually arranged differently for each specic case.
obtained. A 5 Fr sheath was inserted, and selective catheterization of the right pulmonary artery was performed, after
navigation of the catheter via the cardiac chambers.
Angiographic control conrmed the presence of a pulmonary arteriovenous communication in the right lower pulmonary lobe (Fig.14.1a). A 65cm sheath was inserted in
the right lower lobe pulmonary artery. Selective catheterization of the stula followed with a 2.7 Fr microcatheter
system and embolization with detachable microcoils followed (Fig.14.1b). The initial coils were used as scaffold
to prevent migration in the arterial circulation via the pulmonary veins (Fig.14.1c). Complete exclusion of the mal-
Case Presentation Continuation
Procedure
The procedure was performed under general anaesthe-
sia. Access from the right common femoral vein was
formation was achieved with several microcoils that were
densely packed within the lesion (Fig.14.2). The patient
was very well after the procedure and was discharged the
next morning.
abc
Fig. 14.1 (a) Digital subtraction angiography after catheterization of
the right pulmonary artery that conrms the presence of the malformation at the lower right lobe (white circle). (b) Selective catheterization
of the malformation with a microcatheter. (c) Deployment of the rst
detachable coil that would act as scaffold for the rest. Appropriate sizing is required to avoid coil migration at that stage given the very high
ow of the malformation
a b c
Fig. 14.2 (a) Angiographic picture after deployment of several coils
reveals further component of the lesion that needs to be embolized
(arrow). (b) Further embolization of the lesion (white circle) and coil
packing followed. (c) Angiographic picture conrms the satisfactory
outcome with no ow in the malformation and preservation of the ow
in the rest of the parenchyma
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Toolkit
Suggested Toolkit forEmbolization withMicro
Coils
Vascular access kit: Micropuncture, then 4–6 Fr sheath
Access catheter: 4 or 5Fr angled catheter (vertebral, cobra 1 or 2,
headhunter)
Access wire: 0.035″ inch hydrophilic wire, 180 or 260cm
Microcatheter: 2.2-27Fr with or without 0.016–0.021″ inch
microwire
Microwire: Hydrophilic 0.016–0.021″ angled (20-45°)
Microcolis: 0.016–0.018″ pushable or detachable
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Interventions forAorto-Iliac Disease
https://t.me/medicina_free
AthanasiosSaratzis
15
Case Presentation A 72-year-old lady presented with a
left-sided lower-limb arterial ulceration (three toes were
affected– dry gangrene) and bilateral lower-limb rest pain
(chronic limb-threatening ischaemia). She had a history of
type 2 diabetes mellitus, obesity, ex-smoking habit, precious
bilateral supercial femoral artery subintimal angioplasties
(patent – performed 18 months ago), and had previously
undergone an anterior resection for an early-stage colonic
(sigmoid) malignancy with a curative intent. She was already
on Clopidogrel 75mg once daily and high-dose statin therapy (known to have intermittent claudication). Her baseline
computed tomographic (CT) angiography disclosed a long
calcied occlusion of the left common and external iliac
artery, an occlusion of the proximal right common iliac
artery, and an occluded distal aorta below the renal arteries;
the inferior mesenteric artery was also occluded (note previous colectomy).
Background andIntroduction
Lower-limb peripheral arterial disease (PAD) affects 20%
of people over 55years of age [1] and is the main cause of
lower-limb amputations in developed countries [2]. Often,
patients with PAD develop severe leg pain at rest or necrosis (e.g. ulceration or gangrene), referred to as chronic
limb- threatening ischaemia (CLTI) [3]; CLTI is limb and
life threatening and requires urgent revascularisation or
patients will either lose their leg and/or die [3]. The aorta
and iliac arteries are two of the most common sites
affected in those with CLTI [4]. Patients with CLTI and
aorto-iliac disease typically have severe occlusions of
A. Saratzis (*)
Department of Cardiovascular Sciences, University of Leicester,
Leicester, UK
e-mail: as875@le.ac.uk
their aorta or iliac axis over long arterial segments, which
makes their revascularisation technically complex. Some
46,891 patients underwent revascularisation in the NHS
for CLTI in 2019– 20,828 of them for aorto-iliac disease
[5], based on the National Vascular Registry and Hospital
Episode Statistics (HES). Patients with CLTI and aortoiliac occlusive disease can have revascularisation either
with open surgery or more recently developed minimally
invasive techniques in the form of endovascular treatment.
Endovascular treatment in this instance usually involves a
combination of angioplasty, deployment of stents, or other
techniques [3].
An international multidisciplinary expert group in PAD
and CLTI, the TransAtlantic Inter-Society Consensus
(TASC) force, classied aorto-iliac PAD based on severity
of arterial stenoses or occlusions from grade A (less
severe) to grade D (most severe) [6]. For TASC A/B disease [2], endovascular treatment is the universally established and accepted strategy both in the NHS and globally
[2]. For TASC C/D disease, there is uncertainty regarding
the effectiveness of open surgery vs. endovascular treatment, reected in all guidelines [2]. The fact that endovascular treatments (stents, angioplasties, other endovascular
procedures) have seen great advances in the last 20years
has added even more uncertainty regarding the management of patients with TASC C/D aorto-iliac PAD
(Fig.15.1).
Both open surgery and endovascular treatment in these
patients with occlusive aorto-iliac disease can be associated with signicant complications. This is due to the
complex technical nature of any revascularisation procedure when someone has severe occlusive arterial disease
and the patients’ co-morbidities, who are often frail when
presenting for revascularisation. Open surgery is associated with more blood loss, longer duration of in-hospital
stay after the intervention, a 3% early mortality rate, and
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024
G. Geroulakos et al. (eds.), Mastering Endovascular Techniques, https://doi.org/10.1007/978-3-031-42735-0_15
137
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TASC A
TASC B
TASC C
TASC D
Fig. 15.1 TASC classication for patients with aorto-iliac arterial disease. TASC C and D patients have severe occlusive disease and are
more likely to present with CLTI, i.e., severe symptoms; these patients
will be eligible to take part in EVOCC as there is treatment uncertainty
in this group regarding superiority of surgery over newer endovascular
(minimally invasive) treatment
many peri-operative complications, mostly in the form of
major cardiovascular events [7]. Endovascular treatment
is less invasive, with a 1% early mortality rate and typically no need for post- operative admission to intensive
care [4, 7]. Endovascular treatment of severe AIOD has
evolved considerably with the evolution of iliac stenting
techniques [8]. Kissing iliac stents are associated with
acceptable patency rates, comparable in some cases with
open surgery; however, no high-quality randomised controlled trials comparing open vs. endovascular AIOD
reconstructions are available [9, 10]. Furthermore, a variety of novel endovascular therapeutic approaches have
been reported for AIOD, involving the use of both covered
and bare metal stents in the aorta or iliacs. The Covered
versus Balloon Expandable Stent Trial (COBEST) is the
only high quality randomised trial in this clinical context;
COBEST showed a benet when a covered stent was used
occlusive iliac lesions compared with bare metal stents, in
terms of stent patency [11, 12]. However, the study only
evaluated the performance of iliac scaffolds and did not
assess clinical or cost-effectiveness.
Various parameters may inuence patency when treating severe AIOD with endovascular means, including
stent- positioning, stent-design and the discrepancy
between the stented lumen and aortic lumen or “radial
mismatch” [11, 13, 14]. The latter might cause ow perturbations and thrombus formation. Choosing a conguration with the lowest radial mismatch is the hypothesis that
A. Saratzis
led to the advent of the Covered Endovascular Repair of
the Aortic Bifurcation (CERAB) technique, which aims to
achieve a more “anatomical” distal aortic reconstruction
with three covered stents [14–16], compared to kissing
iliac stents or reconstruction without a covered aortic
stent. To date, results from CERAB series up to 3years
have demonstrated acceptable results [14–16]. In an analysis comparing reconstruction using a covered aortic stent
alongside covered iliac stents for advanced aorto-iliac disease, we showed that the CERAB conguration (covered
stents) is associated with less re- interventions over a
medium term follow-up [17]. The currently available
CERAB studies and those relating to other similar techniques published to date do have a number of limitations,
however. They are mostly single centre cohort studies
from high-volume experienced centres with relatively
limited follow-up. Results have not been replicated in
non-tertiary centres, and longer-term outcomes are lacking. Additionally, the currently available endovascular literature in AIOD has not quantied the degree of calcium
in atherosclerotic plaques, and anatomical data are not
reported uniformly. A direct comparison between bare
metal and covered aortic stents in complex AIOD has also
not been attempted.
A recent multicentre registry led by our group recently
provided real-world practice from 12 European centres
regarding the use of iliac and aortic stents in patients with
severe occlusive aorto-iliac disease. Overall, more than 200
patients underwent endovascular revascularisation for
AIOD, of which 32% had aortic chronic total occlusion
(CTO), 46% had iliac CTO, and 48% presented with
CLTI.In addition, most patients had severe aortic and/or
iliac calcication. Analysis of mid-term outcomes
(17 months of follow-up), revascularisation, or major
amputation between patients with bare metal vs. covered
aortic stents. The only difference was that covered aortic
stents were associated with improved freedom from TLR if
combined with covered iliac stents in a multivariable conditional regression. This is in line with the COBEST trial,
which did show better patency when using covered stents
for occlusive iliac disease. At the moment, a large scale
pragmatic randomised trial assessing clinical and costeffectiveness of endovascular treatments for severe occlusive AIOD is urgently needed. Until then, patients having
endovascular procedures for TASC C and D lesions should
be followed-up carefully and receive best medical therapy
as per current guidance. Further, we have recently published a meta-analysis of 66 observational studies (9319
patients), where we found that primary and secondary
patency of CERAB and kissing stenting at 1 and 3years for
TASC C and D aorto-iliac disease is similar to that of open
surgery (aorto-bi-femoral bypass) [7]– Table15.1.
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