Mechanical thrombectomy after intravenous thrombolysis for acute ischaemic stroke

Mechanical thrombectomy after intravenous thrombolysis for acute ischaemic stroke

Correspondence Mechanical thrombectomy after intravenous thrombolysis for acute ischaemic stroke We read with interest Serge Bracard and colleagues’1...

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Correspondence

Mechanical thrombectomy after intravenous thrombolysis for acute ischaemic stroke We read with interest Serge Bracard and colleagues’1 report of THRACE, a multicentre randomised controlled trial comparing the clinical outcomes of intravenous thrombolysis plus mechanical thrombectomy with intravenous thrombolysis alone in 414 patients with acute ischaemic stroke and proximal cerebral artery occlusion. The strengths of THRACE were centralised randomisation, use of a standard dose of alteplase, minimum losses to follow-up, and an intention-to-treat analysis. However, outcome assessors were not masked to treatment assignment, and this is an important potential source of bias. Stent retriever systems, which have been shown to be better than older generation devices,2 were used for mechanical thrombectomy in 116 (82%) of 141 patients. Angiography and mechanical thrombectomy were cancelled in patients whose National Institutes of Health Stroke Scale score improved by 4 or more points after intravenous thrombolysis. However, the short delay between thrombolysis and randomisation meant that patients were randomly assigned before the effect of thrombolysis was known, and thus, in many cases, thrombectomy had to be cancelled. This process contributed to 59 (29%) of 204 patients assigned to the intervention group not actually receiving thrombectomy, which could have diluted the treatment effect. THRACE is the ninth large randomised controlled trial to compare functional outcomes of endovascular thrombectomy with standard medical care. 3 However, what sets THRACE apart is that, www.thelancet.com/neurology Vol 16 February 2017

beyond demonstration of proximal arterial occlusion on CT or magnetic resonance angiography, imaging criteria were not used to select patients. In this sense, THRACE represents a more pragmatic type of trial, and its results are perhaps more widely generalisable. However, the lack of imaging-based selection criteria, together with crossover of nearly a third of patients in the thrombectomy group to standard medical care and the long time from randomisation to groin puncture, might account for the smaller treatment effect than in other trials. Overall, this is a very welcome addition to the literature. We declare no competing interests.

*Jetan H Badhiwala, Farshad Nassiri, Abhaya V Kulkarni, Julian Spears, Saleh A Almenawer [email protected] Division of Neurosurgery, University of Toronto, Toronto Western Hospital, 399 Bathurst Street, West Wing 4-427, Toronto, Ontario, M5T 2S8 Canada (JHB, FN, AVK, JS); and Division of Neurosurgery and Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada (SAA) 1

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Bracard S, Ducrocq X, Mas JL, et al; on behalf of THRACE investigators. Mechanical thrombectomy after intravenous alteplase versus alteplase alone after stroke (THRACE): a randomised controlled trial. Lancet Neurol 2016; 15: 1138–47. Nogueira RG, Lutsep HL, Gupta R, et al. Trevo versus Merci retrievers for thrombectomy revascularisation of large vessel occlusions in acute ischaemic stroke (TREVO 2): a randomised trial. Lancet 2012; 380: 1231–40. Badhiwala JH, Nassiri F, Alhazzani W, et al. Endovascular thrombectomy for acute ischemic stroke: a meta-analysis. JAMA 2015; 314: 1832–43.

Recent data1 suggest that endovascular treatment with stent retrievers in acute ischaemic stroke due to large vessel anterior circulation occlusion improves clinical outcome. The most important factors in patient selection for endovascular stroke therapy are a substantial acute neurological deficit, a treatable arterial occlusion, and a non-extensive ischaemic core. Although consensus does not exist

on the best neuroimaging technique for assessment of patient eligibility, CT and CT angiography are mainly used to confirm vessel occlusion, whereas different methods are used to estimate the infarct core (CT angiography, Alberta Stroke Program Early CT Score, perfusion imaging, and assessment of collateral circulation).2 I n The Lancet Neurology, Serge Bracard and colleagues3 report data from THRACE, one of the largest thrombectomy studies, with 414 patients randomised. The results showing the efficacy of bridging therapy in stroke due to large vessel anterior circulation occlusion were similar to those from previous trials. The occurrence of atrial fibrillation is not reported, although it is widely recognised to affect clot composition and the likelihood of vessel recanalisation. Therefore, the distribution of atrial fibrillation between the groups might have been unbalanced, representing a possible bias. The effectiveness of fibrinolytic therapy to lyse the thrombus seems proportional to clot density on CT. Increasing clot density is thought to be due to the presence of erythrocytes and interstitial fibrin. Both are dense but more permeable to recombinant tissue plasminogen activator than white cell clots, which contain tightly packed platelets and cellular debris.4 Red cell clots are typical of cardioembolic occlusion and are more prone to late spontaneous recanalisation. More than 70% of the patients in the THRACE trial had MRI. The investigators did not provide details of the sequences in the MRI protocol. If the imaging techniques were not used to select patients on the basis of the size of the infarct core, then why was MRI preferred over CT or CT angiography? We believe that the small core–occlusion paradigm5 through good quality non-enhanced CT and CT angiography might be a simple, alternative, and pragmatic 103

Correspondence

approach to select patients who are eligible for endovascular treatment. We declare no competing interests.

*Nicola Morelli, Eugenia Rota, Emanuele Michieletti, Donata Guidetti [email protected] Neurology Unit, Guglielmo da Saliceto Hospital, Piacenza, Italy (NM, ER, DG); and Radiology Unit, Guglielmo da Saliceto Hospital, Via Taverna 49, 29121 Piacenza, Italy (NM, EM) 1

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Badhiwala JH, Nassiri F, Alhazzani W, et al. Endovascular thrombectomy for acute ischemic stroke: a meta-analysis. JAMA 2015; 314: 1832–43. Jia B, Scalzo F, Agbayani E, Woolf GW, Liu L, Miao Z, Liebeskind DS. Multimodal CT techniques for cerebrovascular and hemodynamic evaluation of ischemic stroke: occlusion, collaterals, and perfusion. Exp Rev Neurother 2016; 16: 515–25. Bracard S, Ducrocq X, Mas JL, et al; on behalf of THRACE investigators. Mechanical thrombectomy after intravenous alteplase versus alteplase alone after stroke (THRACE): a randomised controlled trial. Lancet Neurol 2016; 15: 1138–47. Whitesell RT, Steenburg SD. Imaging findings of acute intravascular thrombus on non-enhanced computed tomography. Emerg Radiol 2014; 21: 271–77. Demchuk AM, Menon B, Goyal M. Imaging-based selection in acute ischemic stroke trials—a quest for imaging sweet spots. Ann N Y Acad Sci 2012; 1268: 63–71.

Authors’ reply We thank Jetan Badhiwala and colleagues for their comments about THRACE.1 We did not select the best candidates for thrombectomy and we agree that the lack of imaging-based selection criteria probably played a part, together with the short time to randomisation, on the treatment effect in THRACE. By design, the time from intravenous thrombolysis to randomisation was shorter than that in other trials. The short randomisation delay contributed to the high rate (42%) of functional independence at 3 months in the intravenous thrombolysis alone group, higher than in other trials. Patients were randomly assigned as soon as possible in the so-called mothership situation, but also in the so-called drip-and-ship in which patients had been transported from 104

community hospitals to intervention centres while tissue plasminogen activator was infused intravenously. The time from randomisation to groin puncture was much higher than that in other trials with a negative effect only in the intravenous thrombolysis plus mechanical thrombectomy group. Short time to randomisation and longer time to groin puncture might account for the smaller treatment effect than in other trials. We thank Nicola Morelli and colleagues for their comments about atrial fibrillation and the use of MRI in THRACE. Unfortunately, we did not collect information on atrial fibrillation and we are thus unable to say whether there was an imbalance of atrial fibrillation between groups. We agree that it is a potential source of bias. However, because of randomisation, we do not expect a substantial difference in prevalence of atrial fibrillation in the two groups. Analysis of clot imaging on CT and on gradient–echo T2 imaging is in progress. Although we have not given details about the sequences of MRI in the protocol, we agree that the small core–occlusion paradigm with good quality non-enhanced CT and CT angiography might be a simple alternative and pragmatic approach to select patients who are eligible for endovascular treatment, especially in uncooperative patients. THRACE was a pragmatic trial and centres were asked to use MRI or CT in accordance with local practice. MRI is preferentially used in France (301 [74%] of 412 patients). The MRI protocol included conventional sequences: diffusion-weighted imaging (DWI), fluid attenuation inversion recovery, gradient echo T2, and 3D time of flight. Perfusion imaging on MRI or CT was not mandatory. In our trial, about a third of patients who had poor baseline DWI Alberta Stroke Program Early

CT scores (0–4) had good clinical outcomes at 3 months and we are working on the DWI volumes–clinical outcome correlations. SB reports grants from the French Ministry of Health during the conduct of the study, personal fees from General Electric Medical Systems, and non-financial support from Microvention Europe. The other authors declare no competing interests.

*Serge Bracard, Xavier Ducrocq, Francis Guillemin, Thierry Moulin, Jean-Louis Mas [email protected] Department of Diagnostic and Interventional Neuroradiology, Hopital Central, 29 avenue marechal de Lattre de Tassigny, 54035 Nancy cedex, France (SB); Department of Neurology, CHU Nancy, France (XD); Department of Clinical Epidemiology, INSERM CIC-EC 1433, University of Lorraine and University Hospital of Nancy, France (FG); Department of Neurology, University Hospital of Besancon, France (TM); and Department of Neruology, Sainte-Anne Hospital and Paris-Descartes University, INSERM U894, Paris, France (JLM) 1

Bracard S, Ducrocq X, Mas JL, et al; on behalf of THRACE investigators. Mechanical thrombectomy after intravenous alteplase versus alteplase alone after stroke (THRACE): a randomised controlled trial. Lancet Neurol 2016; 15: 1138–47.

Severe B-cell-mediated CNS disease secondary to alemtuzumab therapy Alemtuzumab is a pan-lymphocyte depleting anti-CD52 antibody, and is approved as an escalation therapy for patients with multiple sclerosis with active disease defined by clinical or imaging features. In phase 3 clinical trials, the drug was more effective than interferon beta-1a in reducing relapses and brain volume loss.1,2 However, concerns have been raised due to its numerous adverse effects.3 On Dec 17, 2015, a 41-year-old man was referred to our clinic with an apparent acute deterioration of his disease. He had been diagnosed with multiple sclerosis in 2004, after optic neuritis of his right eye with typically disseminated T2 lesions fulfilling diagnostic criteria, prolonged visual evoked potentials (VEPs) and motor evoked potentials, and oligoclonal

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