Journal of Neuroradiology (2014) 41, 151—152
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EDITORIAL
Future directions for endovascular management of patients with acute ischemic stroke For many years, intravenous (IV) thrombolysis using rt-PA has been the gold standard treatment for patients with acute ischemic stroke (AIS), with an enlargement of the time window from 3 to 4.5 hours. In parallel, endovascular treatment (EVT) has progressively evolved from intra-arterial chemical thrombolysis to mechanical thrombectomy (MT). First-generation MT devices were rapidly replaced with second-generation stent-retrievers that have been shown to be superior in terms of recanalization and clinical outcome without increase of symptomatic intracranial hemorrhage [1]. The randomized trials comparing EVT or combined approach (i.e. IV thrombolysis + EVT) to IV thrombolysis alone showed no superiority of EVT [2—4], but they had several limitations, including the long period for inclusion, the small number of patients per center, the inappropriate preoperative imaging, and the use of EVT techniques that were obsolete at the time of publication [5,6]. Nevertheless, these recent data raise several questions: what is the current place of intra-arterial thrombectomy for the treatment of AIS? How can the selection of patients treated by EVT be improved? How can EVT be optimized? Although the place of EVT versus IV thrombolysis remains to be clarified when both treatment are feasible, certain indications are currently acceptable, including contraindications for IV thrombolysis and failure of IV thrombolysis. There are many contraindications for IV thrombolysis. One of the most important is probably when the delay since symptom onset is greater than 4.5 h. Since MT can be performed until 6 h after symptom onset (for anterior circulation; the delay is probably longer for posterior circulation), some patients can still be treated with EVT after IV thrombolysis has become contraindicated. Indications for EVT after IV thrombolysis failure are probably more difficult to define since the delay after which failure has to be diagnosed is unknown. In centers actively practicing EVT, patients usually receive IV thrombolysis immediately after http://dx.doi.org/10.1016/j.neurad.2014.07.001 0150-9861/© 2014 Elsevier Masson SAS. All rights reserved.
diagnostic imaging and are transferred to the angiosuite. In the absence of improvement during the transfer, EVT is initiated. A recent survey in the French centers showed that 90% of the centers perform thrombectomy in case of contraindications for thrombolysis and 65% if no clinical improvement occurs after thrombolysis [7]. The selection of patients who will be treated with EVT is quite important and is based on both clinical and imaging factors. In their recent review, Lee et al. show that clinical factors are significant predictors of outcome after intraarterial therapy for AIS, including age, delay to treatment, stroke severity at presentation, and medical co-morbidities [8]. Similarly age and time from symptom onset to recanalization are identified as the two main prognostic factors of clinical outcome after thrombectomy in the series reported by Raoult et al. [9]. As expected, imaging also plays a significant role in patient selection. The French survey reveals that the majority of centers are using MRI for the diagnosis of AIS [7]. MRI also plays an important role for patients with transient ischemic attack [10]. 3-T high-b-value diffusion-weighted imaging (DWI) is superior to standard b-value DWI in the detection of hyperacute infarction and for the prediction of final infarct size [11]. The detection of salvageable brain by diffusion/perfusion mismatch is certainly a key point, but there are still ongoing discussions regarding the appropriate parameters and thresholds that have to be used. Moreover, trials evaluating clinical outcome after IV thrombolysis or MT according to the presence or absence of target mismatch have led to contradictory results. The initial extent of the ischemic lesion on diffusion imaging as evaluated with ASPECT score predicts symptomatic hemorrhagic risk and clinical outcome and certainly should be included in the selection criteria for MT [12]. At a maximum, total mismatch (normal diffusion with perfusion defect) can be observed, but in a limited percentage of
152 patients (3%), and is associated with favorable outcome after medical treatment [13]. Infarct growth evaluated with diffusion before and after medical treatment is also associated (inversely) with clinical outcome [14]. Thrombus analysis is also part of the selection of the patients for MT. Clot location is precisely evaluated by MRA. Very little is known regarding the analysis of clot composition with imaging, but analysis of thrombus length is feasible, singularly using susceptibility sequences [15]. This parameter seems to play an important role in recanalization and clinical outcome [12]. Collateral circulation also plays an important role in the clinical and radiological outcome after ischemic stroke, but the best technique and the appropriate scale to evaluate it still have to be established by analyzing large series [16]. It would also be important to evaluate perfusion collateral reserve. Perfusion techniques (with CT or MR) play an important role for this purpose [17]. Wake-up stroke is a specific situation in which time of symptom onset is unknown. Diffusion/FLAIR mismatch is, in this circumstance, a useful tool to select patients for an active treatment (IV thrombolysis and/or MT) [18]. Finally, it is quite important to evaluate the technical modalities of the MT in order to optimize this treatment. The performance of treatment under general anesthesia or conscious sedation has probably to be determined with anesthesiologists and neurologists according to the patient’s clinical status [19]. The respective value of the different stent-retrievers has to be compared. The use of the balloon-guiding catheter as well as distal aspiration has to be precisely evaluated. The management of tandem occlusion is still a matter of debate [20] and larger series are needed to determine the better approach. The results of the current trials (MrClean, Revascat, Thrace, Swift Prime. . .) will be quite important to determine the future place of MT in the management of AIS, but the risk still exists that some of these trials will be negative because of their design. For this reason, continuous improvement in patient selection criteria and technical modalities of MT is very important to be able to analyze current trials and to build, if necessary, future trials integrating the most recent advances in this field.
Disclosure of interest The authors have not supplied their declaration of conflict of interest.
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Laurent Pierot ∗ Azzedine Benaissa Vitor Pereira Karl-Olof Lövblad France ∗
Corresponding author. E-mail address:
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