Endovascular Thrombectomy for Ischemic Stroke Meta-Analysis
What is the efficacy of endovascular thrombectomy for acute ischemic stroke, as gleaned from this meta-analysis using individual patient data from five contemporary trials?
The authors pooled patient-level data from the MR CLEAN, ESCAPE, REVASCAT, SWIFT PRIME, and EXTEND IA trials to evaluate the association between endovascular thrombectomy and functional outcome, as measured by the modified Rankin Scale (mRS) after acute ischemic stroke. These trials were chosen because they emphasized rapid treatment, patient selection with vessel imaging, and contemporary mechanical thrombectomy devices. All of the trials randomized patients to usual care plus endovascular thrombectomy versus usual care alone. Patients in both arms received intravenous (IV) tissue plasminogen activator (tPA), if eligible. To account for differences between the trials, mixed-effect modeling was used with fixed effects for covariates of interest and random effects for trial and treatment allocation within each trial. This approach allows the treatment effect to be represented by the overall treatment effect across the trials, rather than the specific treatment effect of each trial. Analyses were adjusted for clinical and radiographic predictors of outcome.
There were 1,287 patients included in the analyses: 634 assigned to endovascular thrombectomy and 653 assigned to usual care. The cohorts were balanced with the exception of more frequent IV tPA use in the nonintervention group. Patients in the intervention group were more likely to have a better functional outcome at 90 days (mRS score reduction by 1 point; adjusted odds ratio [aOR], 2.49; 95% confidence interval [CI], 1.76-3.53). The patients treated with intervention were also more likely to be functionally independent (mRS 0-2) at 90 days (aOR, 2.71; 95% CI, 2.07-3.55). There was no difference in mortality or symptomatic intracerebral hemorrhage between the two groups. In subgroup analyses, there was a trend toward improvement in functional outcome (measured by a 1-point reduction in mRS) across all groups; including the elderly and patients not treated with IV tPA, although the difference was not significant in patients ages <50 years, those with extensive early ischemic changes on the initial computed tomography (CT) scan, and in patients with distal middle cerebral artery (MCA) (M2) occlusion.
The investigators concluded that endovascular thrombectomy is associated with reduced disability after acute ischemic stroke.
This analysis confirms the benefits of endovascular thrombectomy that were seen in the trials included in the study. The magnitude of this benefit is substantial, with a number needed to treat for a 1-point reduction on the mRS of 2.6. The improvement in functional status was seen across a variety of important clinical subgroups. While in this analysis, endovascular thrombectomy does not appear to reduce mortality, the improvement in functional outcome is a more important measure for most patients and families. Interventional treatment was not associated with safety concerns. The use of individual patient data strengthens the findings from this study. Older trials of endovascular thrombectomy that did not show benefit for intervention were not included, but this is reasonable, as the imaging selection and devices used in these older studies do not reflect contemporary clinical practice. The lack of significant treatments seen in younger patients, those with early ischemic changes on CT, and distal MCA occlusions likely reflect the small number of patients enrolled with these findings. Many of the trials included in this meta-analysis were stopped prematurely after MR CLEAN was published, and this may lead to overestimation of treatment effects, although the consistent results favoring endovascular thrombectomy temper this limitation.
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