Mechanical Thrombectomy in Strokes with Large-Vessel Occlusion Beyond 6 Hours: A Pooled Analysis of Randomized Trials

BACKGROUND AND PURPOSE: Mechanical thrombectomy with or without intravenous thrombolysis is indicated in the acute treatment of ischemic strokes caused by an emergent large-vessel occlusion (ELVO) within 6 hours from symptom onset. However, a significant proportion of patients are referred to comprehensive stroke centers beyond this therapeutic time window. This study performed a pooled analysis of data from trials in which mechanical thrombectomy was performed beyond 6 hours from symptom onset. METHODS: We searched for randomized controlled trials that compared mechanical thrombectomy with the best medical treatment beyond 6 hours for ischemic strokes due to ELVO and reported on between 1990 and April 2018. The intervention group comprised patients treated with mechanical thrombectomy. Statistical analysis was conducted while pooling data and analyzing fixed- or random-effects models as appropriate. RESULTS: Four trials involving 518 stroke patients met the eligibility criteria. There were 267 strokes treated with mechanical thrombectomy, with a median time of 10.8 hours between when the patient was last known to be well to randomization. We observed a significant difference between groups concerning the rate of functional independence at 90 days from stroke, with an absolute difference of 27.5% (odds ratio=3.33, 95% CI=1.81–6.12, p<0.001) and good recanalization (odds ratio=13.17, 95% CI=4.17–41.60, p<0.001) favoring the intervention group. CONCLUSIONS: This meta-analysis confirms the efficacy of mechanical thrombectomy in selected ischemic stroke patients beyond 6 hours from symptom onset. The selection is mainly based on the limited core infarct detected by emergent assessment using neuroimaging techniques.