Efficacy of intravenous thrombolysis beyond 4.5 to 24 hours in patients with isolated posterior circulation acute ischemic stroke

ObjectiveTo compare the functional outcomes and safety of intravenous thrombolysis (IVT) administered within the standard 4.5-hour time window versus an extended window of 4.5 to 24 hours after onset in patients with acute ischemic stroke (AIS) isolated to the posterior circulation.MethodsData from patients with isolated posterior circulation AIS who received IVT between January 2017 and December 2024 were extracted from the Acute Stroke Patients for Stroke Management Quality Evaluation online database (CASE-Ⅱ, NCT04487340). Patients were categorized into the standard window group (onset-to-needle time [ONT] ≤4.5 h) and the extended window group (ONT >4.5 to ≤24 h). The primary outcome was 3-month functional independence (modified Rankin Scale score ≤2). Multivariate logistic regression and propensity score matching were used to compare outcomes. Interaction tests assessed the consistency of the time-window effect across predefined subgroups (age, sex, baseline NIHSS score, presence of large vessel occlusion, thrombolytic agent, TOAST subtype).ResultsAmong 3508 included patients, 3147 were in the standard window group and 361 in the extended window group. The rate of 3-month functional independence did not differ significantly between the extended and standard window groups (80.1% vs. 78.7%; adjusted OR=0.896, 95%CI: 0.655-1.266). This finding remained consistent after propensity score matching (adjusted OR=1.122, 95%CI: 0.724-1.738). In the entire cohort, each 30-minute delay in ONT was associated with a 2.6% decrease in the probability of functional independence (OR=0.974, 95%CI: 0.952-0.996). This negative association was significant only within the standard window group (OR=0.934, 95%CI: 0.887-0.984). Subgroup analysis indicated that the standard window group had a higher rate of functional independence than the extended window group (both interaction P5 or those with large vessel occlusion. No significant differences were observed in safety outcomes, including symptomatic intracranial hemorrhage, early neurological deteriora-tion, and 3-month all-cause mortality.ConclusionFor patients with isolated posterior circulation AIS, IVT administered within 4.5 to 24 hours after onset demonstrates effec-tiveness and safety comparable to treatment within the standard 4.5-hour window.