Australian Institute of Radiography
Case Study The Radiographer 2009; 56 (2): 27–33
Delayed treatment for a case of acute ischaemic stroke using
mechanical embolectomy – the L5 Merci Retriever
J Velkovic1,2, S McEwan1, A Coulthard1,2
Department of Medical Imaging, Level 3 Ned Hanlon Building, Royal Brisbane and Women’s Hospital,
Brisbane, Queensland, Australia.
The University of Queensland, Brisbane, Queensland, Australia.
Abstract Endovascular therapies for acute ischaemic stroke represent important alternatives or adjuncts to thromboly-
sis. A middle-aged male suffered a Thrombolysis in Myocardial Infarction (TIMI) Grade 0 distal left middle cerebral
artery (LMCA) occlusion resulting in right hemiparesis and dysphasia. Intravenous thrombolysis was contraindicated
due to pre-existing anticoagulant therapy and associated risk of intracranial haemorrhage. The patient underwent rescue
mechanical embolectomy with an L5 Merci Retriever, with adjuvant local intra-arterial (IA) thrombolysis. Successful
TIMI Grade 3 restoration of LMCA blood flow occurred within eight hours of ictus. Aphasia resolved within 24 hours,
whilst other motor and speech symptoms gradually improved over 6 months, allowing the patient to resume work and
independent living. Mechanical embolectomy appears to be a safe and effective alternative in cases of delayed presenta-
tion, or where intravenous thrombolysis is contraindicated. Combined mechanical embolectomy and adjuvant IA throm-
bolysis, instituted within eight hours of ictus in an anticoagulated patient, achieved favourable clinical outcome (modified
Rankin Score of 2) without major thromboembolic or haemorrhagic complications.
Keywords: acute ischaemic stroke, delayed treatment, mechanical embolectomy, Merci Retriever.
Stroke is a leading cause of mortality and permanent
disability, and more than 85% are of ischaemic aetiology.1 Outcomes
following stroke have slowly improved as public awareness and
management strategies continually evolve, yet time constraints
of current therapies limit such treatment to fewer than 10% of
potential candidates.1 Acute ischaemic stroke therapy was
revolutionised by the introduction of intravenous (IV) tissue
plasminogen activator (tPA) to recanalise thrombus-occluded
cerebral vessels. Due to blood-brain barrier degradation in
prolonged cerebral ischaemia,2 treatment must be initiated within
three hours of ictus to minimise the risk of haemorrhage into
infarcted brain tissue.3 For patients presenting after the three-hour
threshold, or where contraindications to IV thrombolysis exist2
(for example, pre-existing anticoagulant therapy), mechanical
embolectomy and/or intra-arterial (IA) thrombolysis offer viable
therapeutic alternatives without excess risk of mortality or intra-
cranial haemorrhage.2,4–7 Endovascular stroke therapies possess
inherent advantages,6 including ability to precisely locate and
evaluate angiographically the presence of occlusive clots and
treatment effect, achieve higher effective local concentration of
thrombolytics at the clot site, and opportunity for combining
therapeutic techniques. Unfortunately, endovascular treatment
is time-consuming, resource intensive, limited to specialised Figure 1: The L5 Merci Retriever (Courtesy Concentric Medical).
centres, and may involve procedural complications (vessel
dissection/perforation, vasospasm, thromboembolism).6 The L5 Merci Retriever (Concentric Medical, Mountain View,
Mechanical clot retrieval can achieve vessel recanalisation in CA, USA) is a mechanical clot retrieval (embolectomy) platform,
up to 100% of patients,8 compared to conservative management constructed from a flexible core wire of nitinol (shape memory
(24.1%), or intravenous (46.2%) or intra-arterial (63.2%) throm- metal alloy) and a series of polymeric filaments attached at the
bolysis.5 tip (Figure 1). 4 Platinum tip markers allow the device to be
28 The Radiographer J Velkovic, S McEwan, A Coulthard
Table 1: Definition of mRS, TIMI and GCS.
Modified Rankin Score (MRS)
0 No symptoms
1 No significant disability. Able to carry out all usual activities
2 Slight disability. Able to look after own affairs without assistance, but unable to carry out all previous activities
3 Moderate disability. Requires some help, but able to walk unassisted
4 Moderately severe disability. Unable to attend to own bodily needs without assistance, and unable to walk unassisted
5 Severe disability. Requires constant nursing care and attention, bedridden, incontinent
Thrombolysis in Myocardial Infarction (TIHI)
0 Absence of any antegrade flow beyond a coronary occlusion
1 Faint antegrade coronary flow beyond the occlusion, with incomplete filling of the distal coronary bed
2 Delayed/sluggish antegrade flow with complete filling of the distal territory
3 Normal flow which fills the distal coronary bed completely
Glasgow Coma Score (GCS)
1 No eye opening
2 Eye opening in response to painful stimulus
3 Eye opening to speech
4 Eyes opening spontaneously
Best verbal response
1 No verbal response
2 Incomprehensible sounds. (Moaning but no words.)
3 Inappropriate words. (Random or exclamatory articulated speech, but no conversational exchange)
4 Confused. (The patient responds to questions coherently but there is some disorientation and confusion.)
Oriented. (Patient responds coherently and appropriately to questions such as the patient’s name and age, where they are and why, the
year, month, etc.)
Best motor response
1 No motor response
2 Extension to pain (adduction of arm, internal rotation of shoulder, pronation of forearm, extension of wrist, decerebrate response)
3 Abnormal flexion to pain (adduction of arm, internal rotation of shoulder, pronation of forearm, flexion of wrist, decorticate response)
4 Flexion/Withdrawal to pain (pulls part of body away when painful stimulus applied)
5 Localises to pain. (Purposeful movements towards painful stimuli)
6 Obeys commands. (Patient does as commanded)
visualised fluoroscopically. The L5 Series is the second genera- ineligible for or failing IV thrombolysis, or in conjunction with IA
tion of Merci Retrievers, which saw addition of the polymeric fil- thrombolysis.4,7,10 Additionally, these trials found that higher reca-
aments to increase surface area to improve engagement with clot. nalisation rates resulted in lower mortality and improved clinical
Prior to deployment, the device is navigated across an occluding outcomes, and that recanalisation rates achieved with the Merci
clot within a microcatheter under digital subtraction angiography Retriever improved with adjuvant use of IA thromboysis.7
(DSA) guidance. As the Merci Retriever is unsheathed from the Numerous clinical variables utilised in this study allowing
microcatheter, it forms into non-tapering helical loops complete meaningful comparison of clinical and angiographic findings
with incorporated filaments which trap and remove blood clot.9 and treatment effect observed in stroke patients are presented
The Merci Retriever was evaluated in the Mechanical Embolus in Table 1. The modified Rankin Score (mRS) is a widely-used,
Removal in Cerebral Ischaemia (MERCI) and MultiMERCI simple overall assessment of neurological function following
trials, and found initially to be safe and effective in patients various forms of brain injury (0 is normal, higher mRS equates to
Delayed treatment for a case of acute ischaemic stroke using mechanical embolectomy – the L5 Merci Retriever The Radiographer 29
Figure 3a: Non-subtracted left carotid artery angiogram demonstrating LMCA
Figure 2: Initial non-contrast cranial CT demonstrates loss of grey-white
matter differentiation and hypodensity (region within oval). The same region
within the right hemisphere has an intact grey-white matter interface (arrows).
Figure 3b: Left carotid artery DSA demonstrating LMCA occlusion (arrow). Figure 3c: Vasospasm of internal carotid artery (arrow).
30 The Radiographer J Velkovic, S McEwan, A Coulthard
Figure 4b: Merci Retriever (arrowhead) deployed distal to the occluding clot
Figure 4a: Microcatheter navigated beyond location of clot (arrow), demon-
strating patent distal LMCA vascular bed.
Figure 4c: Merci Retriever is retracted back towards the carotid bifurcation, Figure 4d: TIMI 3 flow re-established after clot removal (arrow). New-onset
engaging the clot. LACA occlusion (arrowhead).
Delayed treatment for a case of acute ischaemic stroke using mechanical embolectomy – the L5 Merci Retriever The Radiographer 31
worse outcome). The Glasgow Coma Score (GCS), and National
Institute of Heath Stroke Score (NIHSS) in particular for stroke,
are alternative rating scales used to record neurological status
and injury severity. Normally, GCS and NIHSS are 15 and 0
respectively. Decreased GCS and increased NIHSS each repre-
sent worsening neurological function. The NIHSS is a 42-point
rating scale, and further detail may be obtained in Lyden, Brott
and Tilley, et al.11 Thrombolysis in Myocardial Infarction (TIMI)
describes the extent of blood flow observed angiographically in
occluded blood vessels, with increasing TIMI rating correspond-
ing to improved blood flow and distal perfusion. International
Normalised Ratio (INR) is a medical laboratory index describing
the extent of anticoagulation achieved over baseline by medica-
tions such as warfarin. Patients with an abnormal heart rhythm
(atrial fibrillation), blood clots (deep vein thrombosis, pulmonary
embolism), or mechanical heart valves often require long-term
anticoagulation to prevent thrombotic complications. INR is vital
for titrating anticoagulant dose to ensure therapeutic and safe
anticoagulation. INR is approximately 1.0 in healthy individuals,
and on anticoagulant treatment ideally lies between 2.0 to 3.0 for
atrial fibrillation/venous thrombosis and 2.5 to 3.5 for mechanical
This case report describes an episode of acute ischaemic stroke
Figure 5: Right carotid DSA demonstrating collateral filling of LACA (arrow-
in a previously anticoagulated patient, subsequently treated with heads).
a Merci Retriever and adjunctive IA tPA, that resulted in favour-
able clinical outcome. The intention to use case information for distal LMCA and its branches (Figure 4d).
publication was discussed with the patient, who provided valid Unfortunately, a new occlusion was then observed in the proxi-
informed consent to allow use of non-identifiable clinical records mal left anterior cerebral artery (LACA) on a repeat DSA (Figure
and medical imaging for this report. 4d). This represented either a procedural thromboembolic event
(clot formation on catheters/guidewires and subsequent embolisa-
tion), or embolisation of a fragment of the original thrombus as
A 55-year-old male with a history of aortic valve replacement
it was being removed. IA tPA was delivered via microcatheter to
(AVR), long-term warfarin therapy, and smoking, experienced
lyse the clot. A left femoral artery puncture was performed, and
sudden onset expressive aphasia and right hemiplegia at approxi-
DSA of the right internal carotid artery demonstrated excellent
mately 6.30 am. GCS was 11 and NIHSS was 6 upon presentation
collateral circulation through the anterior communicating arteries
to the Emergency Department. Initial non-contrast cranial CT
and filling of the left anterior cerebral artery (LACA) (Figure 5).
demonstrated no evidence of intracranial haemorrhage, but there
Bilateral carotid DSA revealed TIMI Grade 3 patency of LACA,
was a subtle loss of grey-white matter differentiation in the left
LMCA and no new clot formation. Femoral arterial access clo-
fronto-parietal region (Figure 2). The patient was reviewed by
sure was achieved with Angio-Seal (St Jude Medical, MN, USA)
the hospital Stroke Team approximately four hours post-ictus. IV
(right groin) and Starclose (Abbot Vascular, CA, USA) (left groin)
thrombolysis was contraindicated due to an elevated INR of 1.9
vascular closure devices. Histologic analysis of the retrieved clot
(subtherapeutic INR for an AVR), and the patient was referred for
revealed a high platelet content, with absence of tumour cells and
cerebral angiography and possible neuro-endovacular therapy.
Digital subtraction angiography (DSA) of the intracranial ves-
The patient was transferred to the Intensive Care Unit (ICU)
sels via right common femoral artery puncture was undertaken
and extubated the following day. Aphasia resolved on the first
six hours post-ictus under general anaesthesia. This revealed a
day post-procedure, with residual expressive dysphasia. After
TIMI Grade 0 distal left middle cerebral artery (LMCA) occlu-
three weeks, normal ambulation had returned and further speech
sion (Figure 3a, 3b). An eight French (Fr) balloon guide catheter
improvement had occurred. The patient was discharged after four
was navigated through the left internal carotid artery, inducing
months; five weeks of which was spent in medical rehabilitation.
significant vasospasm in the process (Figure 3c). Glyceryl trini-
Within two weeks of discharge, the patient had returned to part-
trate (GTN), a drug capable of inducing vascular smooth muscle
time work and resumed driving. Onset of depression and episodes
relaxation and vasodilation, was infused into the artery to resolve
of short-term memory loss hampered further clinical improve-
the vasospasm. A Merci microcatheter was navigated across the
ment beyond mRS of 2.
occluding clot, demonstrating TIMI Grade 3 blood flow distally
(Figure 4a). Following 500 units of IV heparin, a Merci Retriever Imaging findings
(L5 series) was navigated distal to the clot and an initial attempt There was no evidence of intracranial haemorrhage on initial
made to retrieve it (Figure 4b, 4c). A small quantity of material non-contrast cranial CT, but a loss of grey-white matter differ-
was retrieved without observable flow improvement. Local IA entiation in the left fronto-parietal region was apparent (Figure
microcatheter delivery of two milligrams of (tPA) was performed 2). DSA revealed a distal LMCA occlusion, with patency of
to lyse the clot, and the Merci Retriever re-deployed. lateral lenticulostriate, anterior temporal and temporo-occipital
A second pass of the Merci Retriever resulted in recovery of arteries maintained (Figures 3a, 3b). Two attempts at mechani-
a small firm, thrombus.TIMI Grade 3 flow was observed in the cal embolectomy with a Merci Retriever were made (Figures 4b,
32 The Radiographer S McEwan, J Velkovic, A Coulthard
Figure 6a: Post-embolectomy bilateral carotid DSA demonstrates region of
contrast staining (arrowheads).
Figure 6b: Post-procedure non-contrast CT, demonstrating extravasation of
procedural contrast into brain parenchyma.
Figure 6c: Diffusion-weighted imaging (DWI) demonstrates a hyperintense Figure 6d: Apparent diffusion coefficient (ADC) map demonstrates a zone of
(brighter than surrounding tissue) zone of restricted diffusion in the left tem- hypointensity (darker than surrounding tissue), representing decreased diffu-
poral, frontal and insular regions, suggestive of acute ischaemia. Ischaemia sion coefficient and corresponding to the DWI abnormality. This reinforces an
causes cellular membrane dysfunction and decreased water molecule motion. ischaemic aetiology for the observed MRI abnormalities.
Delayed treatment for a case of acute ischaemic stroke using mechanical embolectomy – the L5 Merci Retriever The Radiographer 33
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allowed for a more favourable clinical outcome than would have
otherwise been achieved.
The authors have no financial disclosures relevant to this