Endovascular Thrombectomy for Large-Vessel Ischemic Stroke
What is the efficacy of endovascular thrombectomy over standard medical care in patients with acute ischemic stroke across the diverse populations included?
The investigators formed the HERMES (Highly Effective Reperfusion evaluated in Multiple Endovascular Stroke Trials) collaboration to pool patient-level data from five trials (MR CLEAN, ESCAPE, REVASCAT, SWIFT PRIME, and EXTEND IA) conducted between December 2010, and December 2014. In these trials, patients with acute ischemic stroke caused by occlusion of the proximal anterior artery circulation were randomly assigned to receive either endovascular thrombectomy within 12 hours of symptom onset or standard care (control), with a primary outcome of reduced disability on the modified Rankin Scale (mRS) at 90 days. By direct access to the study databases, the authors extracted individual patient data that were used to assess the primary outcome of reduced disability on mRS at 90 days in the pooled population and examine heterogeneity of this treatment effect across prespecified subgroups. To account for between-trial variance, they used mixed-effects modeling with random effects for parameters of interest. The authors then used mixed-effects ordinal logistic regression models to calculate common odds ratios (cORs) for the primary outcome in the whole population (shift analysis) and in subgroups after adjustment for age, sex, baseline stroke severity (National Institutes of Health Stroke Scale score), site of occlusion (internal carotid artery vs. M1 segment of middle cerebral artery vs. M2 segment of middle cerebral artery), intravenous alteplase (yes vs. no), baseline Alberta Stroke Program Early CT score, and time from stroke onset to randomization.
Individual data for 1,287 patients (634 assigned to endovascular thrombectomy, 653 assigned to control) were analyzed. Endovascular thrombectomy led to significantly reduced disability at 90 days compared with control (adjusted cOR, 2.49; 95% confidence interval [CI], 1.76–3.53; p < 0.0001). The number needed to treat with endovascular thrombectomy to reduce disability by at least one level on mRS for one patient was 2.6. Subgroup analysis of the primary endpoint showed no heterogeneity of treatment effect across prespecified subgroups for reduced disability (pinteraction = 0.43). Effect sizes favoring endovascular thrombectomy over control were present in several strata of special interest, including in patients ages 80 years or older (cOR, 3.68; 95% CI, 1.95–6.92), those randomized more than 300 minutes after symptom onset (1.76, 1.05–2.97), and those not eligible for intravenous alteplase (2.43, 1.30–4.55). Mortality at 90 days and risk of parenchymal hematoma and symptomatic intracranial hemorrhage did not differ between populations.
The authors concluded that endovascular thrombectomy is of benefit to most patients with acute ischemic stroke caused by occlusion of the proximal anterior circulation, irrespective of patient characteristics or geographical location.
This pooled analysis of patient-level data suggests that modern endovascular thrombectomy added to best medical therapy more than doubles the odds of reduced disability score compared with best medical therapy alone in patients with acute ischemic stroke due to anterior circulation large vessel occlusion. Furthermore, the benefit of endovascular thrombectomy is across a range of subgroups, including in groups of interest such as the elderly, patients not receiving intravenous alteplase, and patients who present later than 300 minutes from stroke symptom onset. The analysis suggests that in clinical practice, endovascular therapy for stroke should not be withheld solely on the basis of advanced age, moderately extensive early ischemic changes on baseline computed tomography, and moderate or severe clinical deficit, but should be based on specific clinical and radiological features of the individual patient.
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