BackgroundIn 2018, the time window for mechanical thrombectomy eligibility in patients with acute ischemic stroke increased from within 6 hours to within 24 hours of symptom onset. The purpose of this study was to evaluate the effect of window expansion on procedural and hospital volumes and patient outcomes at a national level.MethodsWe conducted a retrospective cohort study of patients with acute ischemic stroke undergoing mechanical thrombectomy using data from the National Inpatient Sample. We compared the numbers of mechanical thrombectomy procedures and performing hospitals between 2017 and 2019 in the USA, and the proportion of patients discharged home/self-care, those with in-hospital mortality and post-procedural intracranial hemorrhage (2019 vs 2017) after adjustment for potential confounders.ResultsThe number of patients with ischemic stroke who underwent mechanical thrombectomy increased from 16 960 in 2017 to 28 120 in 2019. There was an increase in the number of hospitals performing mechanical thrombectomy (501 in 2017, 585 in 2019) and those performing ≥50 procedures/year (97 in 2017, 199 in 2019; P<0.001). The odds of in-hospital mortality decreased (OR 0.79, 95% CI 0.66 to 0.94, P=0.008) and the odds of intracranial hemorrhage increased (OR 1.18, 95% CI 1.06 to 1.31, P=0.003) in 2019 compared with 2017, with no change in odds of discharge to home.ConclusionsThe window expansion for mechanical thrombectomy for patients with acute ischemic stroke was associated with an increase in the numbers of mechanical thrombectomy procedures and performing hospitals with a reduction of in-hospital mortality in the USA.