Endovascular thrombectomy beyond 24 hours from ischemic stroke onset: a propensity score matched cohort study

Background The safety and functional outcome of endovascular thrombectomy (EVT) in the very late (VL; >24 hours) time window from ischemic stroke onset remains undetermined. Methods Using data from a national stroke registry, we used propensity score matched (PSM) individual level data of patients who underwent EVT, selected with CT perfusion or non-contrast CT/CT angiography, between October 2015 and March 2020. Functional and safety outcomes were assessed in both late (6-24 hours) and VL time windows. Subgroup analysis was performed of imaging selection modality in the VL time window. Results We included 1150 patients (late window: 1046 (208 after PSM); VL window: 104 (104 after PSM)). Compared with EVT treatment initiation between 6 and 24 hours, patients treated in the VL window had similar modified Rankin Scale (mRS) scores at discharge (ordinal shift; common OR=1.08, 95% CI 0.69 to 1.47, p=0.70). No significant differences in achieving good functional outcome (mRS <= 2 at discharge; 28.8% (VL) vs 29.3% (late), OR=0.97, 95% CI 0.58 to 1.64, p=0.93), successful reperfusion (modified Thrombolysis in Cerebral Infarction score of 2b-3) (p=0.77), or safety outcomes of symptomatic intracranial hemorrhage (p=0.43) and inhospital mortality (p=0.23) were demonstrated. In the VL window, there was no significant difference in functional outcome among patients selected with perfusion versus those selected without perfusion imaging (common OR=1.38, 95% CI 0.81 to 1.76, p=0.18). Conclusion In this real world study, EVT beyond 24 hours from stroke onset or last known well appeared to be feasible, with comparable safety and functional outcomes to EVT initiation between 6 and 24 hours. Randomized trials assessing the efficacy of EVT in the VL window are warranted, but may only be feasible with a large international collaborative approach.