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 1 Department of Medical Imaging, Level 3 Ned Hanlon Building, Royal Brisbane and Women’s Hospital, Brisbane, Queensland, Australia. 2 The University of Queensland, Brisbane, Queensland, Australia. Correspondence email@example.com 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. Introduction 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. Scale Definition 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 6 Dead 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) Eye opening 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 5 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 occlusion (arrow). 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 (arrow). 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 heart valves. 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- Case report 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. cholesterol. 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 4c), interspersed with IA microcatheter delivery of tPA to the References thrombus site. 1 Gandhi CD, Christiano LD, Prestigiacomo CJ. Endovascular management of Following successful TIMI Grade 3 flow restoration to the acute ischemic stroke. Neurosurg Focus 2009; 26(3): E2. LMCA vascular bed, a new-onset TIMI 0 flow defect of the 2 Patel RAG, Collins TJ. Techniques for acute stroke intervention. J Interv LACA was noted on DSA (Figure 4d). Following failed attempts Cardiol. 2009; 22 (1): 1–8. at revascularisation with IA tPA, a right carotid DSA demon- 3 The National Institute of Neurological Disorders and Stroke rt-PA Stroke strated excellent LACA flow via right anterior communicating Study Group. Tissue plasminogen activator for acute ischemic stroke. N Engl J Med. 1995; 333 (24): 1581–8. branch collateral circulation (Figure 5), indicating a reduced risk 4 Smith WS, for the Multi MI. Safety of mechanical thrombectomy and intrave- of infarction to the left frontal lobe. nous tissue plasminogen activator in acute ischemic stroke. Results of the multi Bilateral carotid DSA (Figure 6a) and non-contrast CT (Figure mechanical embolus removal in cerebral ischemia (MERCI) trial, Part I. AJNR 6b) performed at the conclusion of the procedure demonstrated Am J Neuroradiol. 2006; 27 (6): 1177–82. contrast staining of the left fronto-parietal region, suggesting 5 Nogueira RG, Yoo AJ, Buonanno FS, et al. Endovascular approaches to acute reperfusion injury and breakdown of the blood-brain barrier.2,12 stroke, Part 2: A Comprehensive review of studies and trials. AJNR Am J Post-procedure cranial MRI revealed a region of reduced diffusion Neuroradiol 2009 April 22, 2009: ajnr.A1604. (hyperintense region on diffusion-weighted (DWI) MRI) (Figure 6 Gralla J, Brekenfeld C, Arnold M, et al. Acute stroke: Present and future of 6c), which corresponded to the hypodense brain parenchyma catheter-based interventions. Herz 2008; 33 (7): 507–17. identified in the initial cranial CT (Figure 2). Reduced diffusion 7 Smith WS, Sung G, Saver J, et al. Mechanical thrombectomy for acute isch- emic stroke: Final results of the multi MERCI Trial. Stroke 2008; 39 (4): (hyperintensity on DWI) is a feature of acute cerebral ischaemia 1205–12. visible from 30 minutes up to five days post-ictus, whereby water 8 Bose A, Henkes H, Alfke K, et al. The penumbra system: A mechanical molecules accumulate intra-cellularly secondary to deranged cel- device for the treatment of acute stroke due to thromboembolism. AJNR Am J lular transport mechanisms and restricted mobility.13 However, Neuroradiol 2008; 29 (7): 1409–13. DWI abnormalities may also result from pressure, thermal or 9 Nogueira RG, Schwamm LH, Hirsch JA. Endovascular approaches to acute ionic gradients, so apparent diffusion coefficient (ADC) maps are stroke, Part 1: Drugs, devices, and data. AJNR Am J Neuroradiol 2009; 30 (4): generated to identify brain tissue that is truly infarcted.13 ADC 649–61. mapping in this case showed an area of hypointensity (Figure 6d) 10 Josephson SA, Saver JL, Smith WS; Merci and Multi Merci Investigators. that coincided with the DWI abnormality, suggesting acute isch- Comparison of mechanical embolectomy and intra-arterial thrombolysis in aemia. DWI and the ADC map identify regions of brain that will acute ischemic stroke within the MCA: MERCI and Multi MERCI compared to PROACT II. Neurocrit Care 2009; 10 (1): 43–9. invariably become infarcted,13 which has important management 11 Lyden PM, Brott TM, Tilley BP, et al. Improved reliability of the NIH stroke and prognostic complications. Carotid Doppler ultrasound was scale using video training. Stroke 1994; 25 (11): 2220–6. performed due to suspicion of carotid atheromatous disease, but 12 Nakano S, Iseda T, Yoneyama T, et al. Early CT signs in patients with acute failed to detect any significant abnormality. middle cerebral artery occlusion: incidence of contrast staining and hemor- Summary rhagic transformations after intra-arterial reperfusion therapy. Clin Imaging 2006; 30 (4): 297. Treatment of acute stroke depends on timely intervention. This 13 Srinivasan A, Goyal M, Azri FA, et al. State-of-the-art imaging of acute stroke. patient was unsuited to thrombolytic treatment and demonstrated Radiographics 2006; 26 (suppl_1): S75–95. signs of a dense LMCA stroke at the time of mechanical interven- tion. Use of the mechanical clot retrieval device (Merci Retriever) allowed for a more favourable clinical outcome than would have otherwise been achieved. Acknowledgements The authors have no financial disclosures relevant to this study.
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