Background The off-hour effect has been observed in the medical care of acute ischemic stroke. However, it remains unclear if time of arrival affects revascularization rates and outcomes after endovascular therapy (EVT) for emergent large vessel occlusion (ELVO). We aimed to investigate the clinical outcomes of EVT between on-hour and off-hour admissions.

Methods Patients who underwent EVT for ELVO from January 2013 to June 2019 from the STAR Registry were included. Patients were grouped based on time of groin puncture: on-hour period (Monday through Friday, 7:00 am–4:59 pm) and off-hour period (overnight 5:00pm–6:59am and the weekends). Primary outcome was final modified Rankin Scale (mRS) at 90 days on mRS-shift analysis.

Results A total of 1919 patients were included in the study from six centers. The majority of patients (1169, 60.9%) of patients presented during the off-hour period. The mean age was 68.1 years and 50.5% were women. Successful reperfusion, as defined by a Thrombolysis In Cerebral Infarction (TICI) score of ≥2B, was achieved in 88.8% in the on-hour group and 88.0% in the off-hour group. Good clinical outcome (mRS 0–2) was obtained in 34.4% of off-hour patients and 37.7% of on-hour patients. On multivariable ordinal logistic regression analysis, time of presentation was not associated with worsened outcome (OR 1.150; 95% CI 0.96 to 1.37; P=0.122). Age, admission National Institutes of Health Stroke Scale (NIHSS), baseline mRS, and final TICI score were significantly associated with worse outcomes.

Conclusion There is no statistical difference in functional outcome in acute ischemic stroke patients who underwent EVT during on-hours versus off-hours.