BackgroundDifferent studies have demonstrated the benefit of endovascular treatment (EVT) up to 24 hours after acute ischemic stroke (AIS) onset. Recent cohort observational studies suggest that patients with large vessel occlusion AIS may benefit from EVT beyond 24 hours from the last known well (LKW) when adequately selected. We aimed to examine the safety and efficacy of EVT beyond 24 hours from LKW using a meta-analysis of all the literature available.MethodsA systematic search from inception to April 2023 was conducted for studies including AIS patients with EVT beyond 24 hours from LKW in Medline, Embase, Scopus, and Web of Science. Outcomes of interest included favorable functional outcome (90-day modified Rankin scale (mRS) 0–2), successful reperfusion (modified Thrombolysis in Cerebral Infarction (mTICI) 2b-3), symptomatic intracerebral hemorrhage (sICH), and 90-day mortality. Data were pooled using a random-effects model.ResultsTwelve studies with 894 patients were included. The rate of favorable functional outcome was 40% (95% CI 31% to 49%; I²=76%). The rate of successful reperfusion was 83% (95% CI 80% to 85%; I²=0%). The sICH rate was 7% (95% CI 5% to 9%; I²=0%) and the 90-day mortality rate was 28% (95% CI 24% to 33%; I²=0%). There was no significant difference in favorable outcomes (OR=0.69; 95% CI 0.41 to 1.14) and 90-day mortality (OR=1.35; 95% CI 0.90 to 2.00) among patients who underwent EVT <24 hours versus >24 hours.ConclusionsEVT beyond 24 hours from LKW may achieve favorable clinical outcomes and high reperfusion rates, with acceptable intracranial hemorrhage rates in selected patients. Considering the current certainty of the evidence and heterogenous individual study results, larger prospective trials are warranted.