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Endovascular Treatment ofAcute Stroke
LeveJosephDevarajanSebastian andSavyasachiJain
12
Key Messages
1. Current trials and guidelines have opened new vistas and
a surge in demand for endovascular management in acute
stroke.
2. Imaging techniques like multiphasic CT angiography, CT
perfusion, or MRI and MR perfusion help in the management of acute stroke.
3. Working algorithm for the management of acute stroke is
essential.
4. Neurointerventionists should be aware of all the technical
aspects of mechanical thrombectomy.
12.1 Introduction
Large vessel occlusions (LVOs) account for up to 40% of
acute ischemic strokes (AIS) worldwide and a greater proportion of disabling or fatal strokes [1]. Re-establishing cerebral perfusion by quickly recanalizing the occluded vessel
(within a certain short time frame) has been proven in many
randomized clinical trials to improve clinical outcomes.
Historically, intravenous infusion of thrombolytic agents
(IVT), intra-arterial thrombolysis (IAT), and mechanical
thrombectomy were the methods employed to recanalize
acute LVOs. IVT along with supportive medical management, which came to be termed as “standard medical treatment for acute stroke,” has been the mainstay of treatment
for the early window (<4.5h from stroke onset, now being
extended up to 9h) LVO strokes. First-generation mechanical thrombectomy (MT) devices were not efcient in recanalizing the LVOs, and, hence, standard medical treatment
retained its primacy till the second decade of the current century when newer (second generation) devices, namely, stentrievers and aspiration catheters, were introduced. The
publication, in 2015, of the results of the ve landmark trials
L. J. D. Sebastian (*) · S. Jain
Department of Neuroimaging and Interventional Neuro-radiology,
All India Institute of Medical Sciences, Delhi, India
(MR-CLEAN, SWIFT-PRIME, REVASCAT, ESCAPE, and
EXTEND-IA) that employed these newer MT devices established the superiority of endovascular treatment over standard medical treatment alone in LVO stroke [2–6].
Consequently, the American Heart Association (AHA) and
the American Stroke Association (ASA) 2018 guidelines
gave a class I recommendation for MT with stentrievers for
AIS due to LVO in adults (>18years) in whom treatment can
be initiated within 6h of stroke onset [7]. Even those presenting in a 6–24-h time window can benet from MT subject to meeting certain imaging-based eligibility criteria as
per DAWN or DEFUSE3 trials.
These trial results and guidelines have opened new vistas
and a surge in demand for neurointerventionalists. Yet the
rigors of day-to-day practice dictate that one pays attention
to the following two important aspects to be able to provide
a fruitful service. They are (1) case selection and (2) knowledge and skill in various endovascular techniques. We
attempt to address the same in brief in the following
sections.
12.2 Case Selection forMechanical
Thrombectomy
A review of basic pathophysiological mechanisms of acute
stroke that underlie the case selection principles is pertinent
here.
(i) Brain tissue cannot tolerate ischemia for long. A few
minutes after LVO, a variable number of brain cells in
the supply area begin to die. The growing volume of
such irreversibly injured brain tissue is called core
(infarct). Similarly, a surrounding or adjacent volume
of tissue supplied by the now-occluded artery manages
to survive by drawing some perfusion from the adjacent
circulation through “collaterals.” This surviving but
dysfunctional tissue is named penumbra [8].
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024
S. H. Chandrashekhara (ed.), Textbook of Interventional Radiology, https://doi.org/10.1007/978-981-97-9601-4_12
119
120
L. J. D. Sebastian and S. Jain
(ii) With time, more of the penumbra succumbs to isch-
emia, i.e., the core enlarges, unless blood ow is
restored to the region. Time is the most important variable inuencing core growth and so is the adage: “Time
is Brain.”
(iii) However, the rate of growth of core may vary among
individual patients. Thus, there are “fast growers” and
“slow growers” as well. The status of collaterals, or
more precisely the failure of the same, is the most
important factor affecting the rate of infarct growth.
(iv) Hence, in a given patient, apart from assessing the
chronological timing of stroke onset, we have to assess
the core-penumbra status also at the time of presentation. The latter is termed “tissue-timing.” Imaging
techniques like multiphasic CT angiography, CT perfusion, or MRI and MR perfusion help in this regard.
Those with a substantial volume of penumbra will benet from the recanalization of the LVO.
In spite of advances in the understanding of stroke pathophysiology as outlined above, it is nearly impossible to prescribe a set of uniform or denite selection criteria that can
determine the eligibility of a random patient presenting with
AIS for endovascular treatment. Based on the data collated
from multiple RCTs and the guidelines prescribed by AHA,
the following working algorithm can be drawn up:
(i) The most important variables to be considered are age,
pre-stroke morbidity, severity at presentation as best
represented by the National Institute of Health Stroke
Scale (NIHSS), time of onset, level of vascular occlusion, and status of brain parenchyma as determined by
imaging. Adult patients (>18 years) with pre-stroke
morbidity modied Rankin score (mRS) ≤2, acute large
vessel occlusion, signicant neurological decits
(NIHSS>6), and presenting within 24h are considered
eligible for MT [7].
(ii) NCCT is acquired as the rst step in the imaging
workup, primarily to rule out intracranial hemorrhage.
If an acute infarct is seen, the area involved is graded
using the Alberta Stroke Program Early CT Score
(ASPECTS), which is available both for middle cerebral artery (MCA) and posterior circulation infarcts, but
has been clinically validated only for the former. The
CT angiogram is used to locate the level of vascular
occlusion.
(iii) For anterior circulation, LVOs further management
depends on the duration from stroke onset. If it is <6h,
(a) If there is clinical-radiological mismatch, i.e., there
is a signicant neurological decit (NIHSS> 6)
and minimal or no infarct on NCCT
(ASPECTS>6), the patient can be shifted for MT
after bridging IVT, and no further imaging workup
is needed.
(b) In the rare instance of signicant infarct on NCCT
(ASPECTS ≤ 6), penumbral imaging is done as
described in the next step.
(iv) For onset of 6–24 h and wake up stokes or stroke of
uncertain time of onset, advanced penumbral imaging is
done as follows:
(a) Multiphasic CT angiogram is used to grade
collaterals.
(b) CT perfusion study provides the brain perfusion
parameters of cerebral blood volume (CBV), cerebral blood ow (CBF), and time to maximum
(TMax). Reduced CBV denotes the core, while
CBF is reduced in the whole ischemic tissue,
including the penumbra. Penumbra shows reduction in CBF by 40%, which is thus denoted by the
CBV-CBF mismatch. Penumbral tissue shows a
TMax >6s while at the core it is >10s [9].
(c) MRI can also help in timing the stroke, especially
in wake-up stroke where a DWI-FLAIR mismatch
signies an onset <4.5h. ASPECTS is determined
best on DWI images, clarifying doubtful areas on
NCCT.MRI moves a step further in assessing the
penumbra by analyzing the DWI-Perfusion (ASL/
DSC perfusion) mismatch.
(d) Some centers prefer MRI over CT for penumbral
imaging. One should stick to a well-tested protocol
for an institute, based on operator preferences,
logistics, and results.
12.3 Technical Aspects ofMechanical
Thrombectomy (Figs.12.1, 12.2, 12.3
and12.4)
There is no specic method or formula for the successful
conduct of MT. Every interventionalist shall design his
methods based on their training, experience, expertise
acquired thereby, and the logistics available to them. What
follows is a general guidance and a reminder of key aspects.
1. General vs local anesthesia:
Any interventionalist is comfortable performing the
procedure in a still patient. It reduces overall procedure
(recanalization) time and technical injuries (e.g., wire
perforation) as well. However, general anesthesia (GA)
has its own problems too: (i) delay in arranging GA will
waste precious time, and (ii) fall in BP while inducing
GA can lead to crashing of collaterals.
12 Endovascular Treatment ofAcute Stroke
121
a
e
b
f
c
d
g
Fig. 12.1 A 36-year-old gentleman, with previous history of rheumatic
heart disease with mitral valve replacement, presented with left-sided
hemiparesis and facial deviation to right. (a, b) Axial non-contrast CT
images shows that apart from the chronic left MCA infarct (arrow in b),
patient had hypodensities in right corona radiata (arrow in a). (c, d) CT
To circumvent these drawbacks, the anesthesia team
should be readily available and preferably be a part of the
stroke team. The anesthetist should be efcient and well
trained so that quick induction without hypotension is
achieved. Additional care is needed in cardiac patients. In
the absence of such facilities or in cases of co-operative
patients (non-dominant hemispheric stroke), it may be
wiser to proceed with MT under local anesthesia [10].
2. Vascular access and co-axial guidance system:
(a) An 8F femoral short sheath to begin with will save
precious time, and a coaxial system of 6F long sheath
with a diagnostic catheter and 0.35 or 0.32 guidewire
within can be taken directly via the sheath.
angiogram showed acute occlusion in right M1-MCA (arrow in c), with
good collaterals (arrow in d). (e, f, g) CT Perfusion showed reduced
CBF in the MCA territory (arrow in e), but maintained CBV (arrow in
g). Patient was immediately taken up for MT.A hard clot was removed
using Solumbra technique, and TICI-2B recanalization was achieved
(b) Long sheath—diagnostic catheter combinations can
be—80cm+Picard for shorter patients, 90cm long
+120 cm vert/Picard for taller ones or long sheath
+120cm SIM-II for type III aortic arch.
(c) In the rare cases of coarctation or diseased iliac arter-
ies or very unfavorable arch, anatomy radial access
may be preferred [11].
(d) The long sheath-diagnostic catheter combination
should be negotiated straightaway to the target neck
vessel as discerned by the CT angiography.
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L. J. D. Sebastian and S. Jain
Fig. 12.2 Aspiration
thrombectomy. (a, b)
Antero-posterior (a) and
lateral (b) views of right ICA
angiogram shows complete
occlusion of M1 segment of
right MCA (arrows in a & b).
(c) Fluoroscopy under
roadmap guidance shows that
the occlusion is crossed using
a microcatheter and micro
guidewire (white arrow) and
suction catheter (black arrow)
advanced up to the thrombus.
(d) Check angiogram after
suction thrombectomy shows
complete recanalization of
right MCA (arrow)
a
c
b
d
12 Endovascular Treatment ofAcute Stroke
123
a
b
c
Fig. 12.3 Mechanical thrombectomy using stentriever. (a) Antero-
posterior view of left vertebral artery angiogram shows complete occlusion of distal basilar artery (arrow). (b) Lateral angiogram shows
a
Fig. 12.4 Mechanical thrombectomy using stentriever and aspiration.
(a) Antero-posterior view of right CCA angiogram shows occlusion of
M1 segment of right MCA (arrow). (b) Angiogram without subtraction
shows stentriever (arrow) deployed across the thrombus. (c) Angiogram
b
c
stentriever (arrow) deployed from the right posterior cerebral artery into
the basilar artery. (c) Check angiogram after thrombectomy shows
recanalization of the basilar artery (arrow)
d
image showing aspiration catheter (arrow) advanced up to the thrombus. (d) Check angiogram after thrombectomy using Solumbra technique shows complete recanalization of right MCA (arrow)
124
L. J. D. Sebastian and S. Jain
12.4 Thrombectomy Techniques
Subsequent steps depend on the interventionalist’s choice of
devices and technique for thrombectomy. Though a number
of techniques and an equally prolic number of acronyms
are described in the literature, they generally fall in one of
the following: stentriever, aspiration, or combination of both.
Irrespective of the techniques adopted, the goal of MT is to
achieve complete or near complete recanalization of the
occluded vessel and reperfusion of its supply area within a
minimum possible time. Modied thrombolysis in cerebral
infarction (mTICI) score is widely used for assessing recanalization and reperfusion. An mTICI score of 2b or 3 is associated with good clinical outcomes.
12.5 Aspiration Technique
(i) Aspiration or reperfusion catheters are of specialized
ones with attributes that allow them to be navigated distally into the intracranial vessels safely and with ease.
They have wide lumen and do not collapse while applying suction pressure.
(ii) The aspiration catheter is navigated over a microcatheter-
guidewire assembly to the proximal end of the thrombus occluding the artery. The microcatheter is then
removed, and the aspiration catheter is maneuvered to
engage the clot well (Fig.12.2). New generation reperfusion catheters, as per manufacturers’ claim, can be
navigated without the coaxial microcatheter system.
(iii) Once the catheter is placed in the desired position, suc-
tion pump is attached to the hub, and if the clot is well
wedged into the clot, no blood ows to the pump canister. If otherwise, the catheter is to be adjusted to engage
the clot better.
(iv) A dwell time of a few minutes is allowed while the suc-
tion is on. Then the aspiration catheter is slowly pulled
back, and as it reaches the proximal larger artery, blood
may start to ow through the catheter into the canister
which should be checked later for the aspirated clots.
The catheter should be ushed on the table to check for
the aspirated clots.
12.5.1 Stentriever Technique
(i) A 6F guide catheter is placed in the distal cervical inter-
nal carotid artery (ICA) or, in case of straight ICA, in
the petrous or laceral segment. A microcatheter-micro
guidewire combination is then navigated to the target
vessel. A 0.021″ microcatheter is used for most of the
stentrievers, and 0.017″ microcatheter is used for distal
vessels. The occlusion has to be crossed carefully and in
blind, taking care to remember the normal anatomical
disposition of the vessels.
(ii) After crossing the occlusion, the microguidewire is
exchanged for the stentriever which is deployed across
the thrombus by gentle push while unsheathing of
microcatheter at the same time (Fig.12.3).
(iii) After deployment, the stent is left in situ for a few min-
utes, usually 3–6min to allow for full expansion of the
stent and better engagement of clot [12].
(iv) The next step is clot retrieval. The microcatheter is
slightly advanced up to the proximal end of the stent,
and then the entire assembly is pulled out gently and
swiftly. It is a good idea to do manual aspiration of
guide catheter by an assistant using a 50ml syringe during the clot retrieval to avert re-embolization of clot
fragments during the process. Some even prefer to pull
out the guide catheter along with microcatheter-stent
assembly.
(v) A control angiogram is then taken via the long sheath or
guide catheter (if not pulled out). Recanalization is
assessed. If it is less than mTICI 2b, the procedure is
repeated. If the recanalization is not satisfactory even
after 3 or 4 passes, then switching over to another technique or combination of one should be thought of. It
shall be remembered that complication rate increases
with prolonged procedure time and increased number
of passes [13].
12.6 Combination Technique
(i) If one technique is not working, it is better to switch over
to another one or preferably a combination, i.e., aspiration + stentriever technique (also called Solumbra technique). There can be multiple permutations and
combinations of switch over methods [13].
(ii) One of the easier methods is to take the aspiration cath-
eter over a microcatheter-microguidewire assembly till
the supraclinoid ICA. A longer microcatheter, available with some vendors, is very convenient for the purpose. The microcatheter should be placed distally
crossing the thrombus, and then the microguidewire is
exchanged for a stentriever. The aspiration catheter is
then tracked up to the level of the proximal aspect of
the stent/thrombus, and the suction pump is switched
on. The microcatheter is pulled out to allow for more
space and better suction effect. After a few minutes of
dwell time, the stentriver and aspiration catheter assembly is pulled out (Fig.12.4).
12 Endovascular Treatment ofAcute Stroke
125
12.7 Balloon Guide Catheters (BGC)
Proponents claim that it augments clot suction by the aspiration catheter and helps avoid distal non-target embolization
[14]. Counter argument is that ow arrest does not help suction effect and in fact impedes clot engagement and retrieval.
BGC is placed in the cervical ICA and remains out of the
angiographic led of attention most of the time. Hence, one
needs to be mindful about its positioning and its inationdeation as errors can lead to cervical artery dissection. It
adds up another step to an already demanding procedure.
12.8 Special Situations
12.8.1 Posterior Circulation Stroke
Though the techniques described above are for MCA occlusion, the same techniques with some appropriate intuitive
modications can be applied to the posterior circulation and
anterior cerebral artery occlusion. Some points of relevance
for posterior circulation are listed as follows:
(i) MRI is more frequently needed for decision-making.
(ii) MRI (DWI)-based pc-ASPECTS score can help assess
severity and predict functional outcome [15].
(iii) Longer time window even beyond 24h is allowed in
some cases.
(iv) Smaller caliber of vertebral arteries may preclude tri-
axial guiding system, and a simple 6F guide catheter
and stentriever may work in many cases.
(ii) If the bridging IV thrombolysis is administered to the
patient, dual antiplatelets cannot be started immediately after stenting. Single antiplatelet alone can be
started for 24–48h following which a second one can
be added.
12.8.3 Intracranial Atherosclerotic Disease (ICAD)
ICAD as a cause of acute stroke is often a retrospective diagnosis made after the rst or rst few passes when the residual
lumen shows irregularity characteristic of a ruptured atherosclerotic plaque or recurrent occlusions in a few minutes
after each thrombectomy pass. Management options include
thrombectomy followed by intracranial stent deployment
across the culprit lesion or starting antiplatelet infusion
(Abciximab or tiroban) immediately. Successful management with intracranial stent deployment are increasingly
reported in recent times.
12.8.4 Medium Vessel Occlusions (MeVO)
Smaller caliber aspiration catheters and stentrievers are
available for recanalizing medium vessel occlusions like distal M2/M3 MCA, A2/A3 ACA, or P2/P3 PCA. Clot fragmentation and migration to distal vessels during MT in LVOs
are not uncommon, and these devices may be of much use in
such situations.
12.8.2 Tandem Occlusions
(i) In concomitant neck vessel (ICA and vertebral artery)
and intracranial occlusions, both needs to be treated.
Approaches may differ as to which one to treat rst.
Ballon angioplasty of the stenosis at the neck vessel
may be followed by intracranial thrombectomy; nally,
the neck vessel lesion may be stented or left with balloon angioplasty alone [15]. Once stenting is done,
patient has to be kept on antiplatelet agents to prevent
stent thrombosis. Intravenous tiroban infusion is
administered until the loading doses of oral antiplatelet
agents are given. However, in case reperfusion hemorrhage develops, antiplatelet agents will have to be
stopped, increasing the risk of stent thrombosis and reocclusion. Therefore, stenting is done only as a last
resort in case of immediate recoil after angioplasty or
in dissection.
12.9 Complications
Mechanical thrombectomy is associated with a number of
intra and post-procedural complications, with an estimated
rate of around 15% [16]. Some of these complications are
life threatening. Many others are associated with increased
in-hospital stay, higher cost, and increased disability. Some
of the complications can be as follows:
(i) Failure to recanalize optimally: Many factors like dif-
cult anatomy, clot characteristics like excessive clot
burden, “hard” clot, device failure, non-availability of
multiple devices (including cost constraints), and unexpected procedural delays can contribute to failed or
inadequate recanalization (<TICI 2b).
(ii) Distal non-target or new territory embolization: It can
be harmful if a larger territory is involved when attempts
should be made to recanalize the freshly occluded
vessel.
126
L. J. D. Sebastian and S. Jain
(iii) Intracerebral hemorrhage (ICH): It is a potentially seri-
ous complication of MT associated with increase in
morbidity and mortality. It can vary from small petechial or punctate hemorrhages to large hematoma.
Those associated with neurologic deterioration with at
least four points increase in NIHSS are dened as
symptomatic ones (sICH).
(iv) Subarachnoid hemorrhage (SAH): Arterial perforations
by wires or other devices lead to SAH.Minor SAH may
not affect overall outcome. Angiographically visible
extravasation should be managed instantly by measures
like lowering the blood pressure, balloon tamponade,
and temporary coiling if warranted.
(v) Other device-related events: Vasospasm sometimes fol-
lows clot retrieval due to vessel hyperresponsiveness to
device manipulations and can potentially lead to reocclusion. Intra-arterial milrinone or nimodipine are
helpful in relieving vasospasm. Procedure-related arterial dissections can affect intra or extra-cranial arteries
and should be recognized early and managed appropriately. A common site is the clinoidal segment of ICA
where forcing an aspiration catheter along the acute
curve of anterior genu of cavernous ICA can result in
arterial injury. Accidental stent detachment can also
happen. Decision to retrieve or leave the stent in situ
should be taken after careful analysis of angiography
for disposition of stent and ow impediments.
(vi) Malignant infarction: It can occur in up to 10% of
patients. Poor neurological status (high NIHSS) following MT, low baseline ASPECTS, and poor glycemic
control are some of the clinical factors associated with
malignant infarction. Decompressive craniectomy is
indicated in many of these cases [17].
12.10 Immediate Post-procedure Care
The blood pressure should be lowered after successful recanalization to reduce the chances of reperfusion hemorrhage.
However, many studies suggest that intensive blood pressure
control is associated with poor outcome, and hence mild-tomoderate reduction in systolic BP should sufce [18, 19].
Post-procedure CT scan is a must to look for bleed and
infarct growth. Dual-energy CT if available will be very
helpful to differentiate reperfusion bleed and contrast
extravasation.
In patients done under GA, the decision of immediate or
delayed extubation is taken based on the overall patient status, recanalization status, and ndings in the post-procedure
CT scan.
In any case, it is highly desirable to monitor the patient in
an intensive care unit (ICU) or high dependency unit (HDU).
Close monitoring of GCS, blood pressure, blood sugar, and
electrolytes is of paramount importance for bringing out a
better clinical outcome. Follow-up CT scan at 24h is necessary. Further serial scans may be mandated to monitor an
ICH. Sometimes, DWI may be done to assess infarct volume. Serial NIHSS recording is a useful way of clinical
monitoring.
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STROKEAHA.122.041949.
Interventions inIntracranial andSpinal
Arteriovenous Malformations
LeveJosephDevarajanSebastian, NikhilaGunnaReddy,
andSavyasachiJain
13
Key Messages
1. Proper understanding of pathology, angioarchitecture, natural history, varied clinical presentations of cerebral AVMs,
and knowledge of various treatment options are essential for
making optimal therapeutic decisions in clinical practice.
2. Cross-sectional imaging is invaluable to precisely localizing brain AVM and thereby deciding the management.
3. Endovascular treatment remains the mainstay of management for dural AVF.
4. Spinal vascular malformations are uncommon and complex as well as often difcult to diagnose and treat.
13.1 Introduction
Intracranial AVMs can be classied, primarily based on their
compartmentalization, into the following types:
1. Brain/cerebral parenchymal/pial AVMs.
2. Vein of Galen aneurysmal malformation.
3. Dural AV malformations and stulas.
Spinal AVMs will be dealt with in the last section of this
chapter.
13.2 Brain AVMs
13.2.1 Introduction
Brain vascular malformations consist of the following spectrum of vascular lesions [1]:
1. Capillary telangiectasias.
2. Cavernous malformations (also called as cavernomas).
3. Developmental venous anomalies (DVAs).
4. Mixed lesions (cavernoma + DVA).
5. Arterio-venous malformations (AVMs).
Of these, AVMs are distinguished from the other types
by the presence of abnormal arteriovenous shunting and a
higher propensity to bleed. The majority of the symptomatic cerebral AVMs need to be treated, and microneurosurgical removal, endovascular embolization, and
radiosurgical obliteration are the principal therapeutic
modalities employed alone or in various combinations for
the purpose. Proper understanding of pathology, angioarchitecture, natural history, varied clinical presentations of
cerebral AVMs, and knowledge of various treatment
options are essential for making optimal therapeutic decisions in clinical practice. The following subsections intend
to address the same.
13.2.2 Epidemiology
The prevalence of cerebral AVM is not denitely known, but
their incidence in general autopsy is 0.15%, and it has been
estimated that 0.14% and 0.8% of the population may present with a cerebral AVM in a given year [1, 2]. The annual
risk of hemorrhage in an unruptured AVM is 2% yearly, and
the risk of re-rupture in the rst year is >9% [3, 4].
Most of the lesions, in the sense of causative or primary
trigger events, are congenital rather than acquired. In some
syndromes like Rendu-Osler-Weber and Wyburn-Mason
syndrome, multiple brain AVMs are seen. Various postulated
theories state that there is a congenital predisposition that is
triggered later in life by extrinsic/environmental factors [2,
5]. Rhoton et al. found that repressed preproendothelin-1
gene, increased VEGF, and increased angiopoietin receptors
were noted in most cases of brain AVMs.
L. J. D. Sebastian (*) · N. G. Reddy · S. Jain
Department of Neuro-radiology and Neurointerventions, All India
Institute of Medical Sciences, Delhi, India
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024
S. H. Chandrashekhara (ed.), Textbook of Interventional Radiology, https://doi.org/10.1007/978-981-97-9601-4_13
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