A Meta-Analysis of Observational Evidence for the Use of Endovascular Thrombectomy in Proximal Occlusive Stroke Beyond 6 Hours in Patients with Limited Core Infarct

PURPOSE: The safety and efficacy of endovascular thrombectomy (EVT) for patients with proximal occlusive stroke presenting beyond 6 hours and selected on the basis of favorable neuroimaging remains unclear. MATERIALS AND METHODS: A systematic search was performed from four electronic databases from their inception to Jan 2017. A meta-analysis of outcomes from studies with patients treated beyond 6 hours was compared to those treated within the established 6 hour therapeutic window in randomized trials, selected using conventional imaging methods with CT/CT angiography. RESULTS: A total of 8 articles met inclusion criteria for the study population (a prospective single-center study, 5 retrospective single-center studies and 2 retrospective multicenter studies). These were compared to the results of three prospective trials of patients treated within 6 hours selected using CT/CT angiography. For patients treated >6 hours and <6 hours respectively, the weighted mean age was 64.7 vs. 67.0 years; the presenting NIHSS was 15.7 vs. 17.1 and the time from symptom onset to puncture was 4.0 hours vs. 15.1 hours. Weighted pooled estimates of successful recanalization (TIMI 2/3 or TICI 2b/3) and favorable outcome (mRS ≤2) were similar between both groups, 70.1% vs. 70.6%, P=0.75 and 38.9% vs. 38.4%, P=0.88 respectively. Pooled mortality measured at 3 months was 22.8% for those treated >6 hours and 12.5% for <6 hours, P<0.0001. Symptomatic intracranial hemorrhage was not significantly different (10.0% vs. 7.7%, P=0.33). CONCLUSION: When compared to established methods of patient selection, EVT employed beyond 6 hours in those selected with imaging to exclude large core infarcts achieves similar rates of recanalization, and functional outcome but there is a significant increase in mortality despite no increase in symptomatic intracranial hemorrhage.