Abstract WP1: Threshold Volume Associated With Higher Survival After Endovascular Recanalization Therapy of Acute Ischemic Stroke

Background and Purpose: Endovascular recanalization therapy (ERT) is becoming increasingly important in the management of acute ischemic stroke (AIS), but the hospital threshold volume for optimal ERT remains unknown. We investigated whether there was a correlation between hospital volume of ERT and risk-adjusted patient outcomes. Materials and Methods: From the National Health Insurance (NHI) claims data, we selected 11,745 AIS patients who underwent ERT from 2011 to 2015, in 111 hospitals. The outcome measures of the study were 30-day mortality, readmission rate, and symptomatic intracranial hemorrhage (ICH) rate. For each outcome measure, risk-adjusted mortality prediction models incorporating demographic variables, modified Charlson comorbidity index, and clinical stroke severity index (SSI) were built, and validated through a comparison with two independent hospital registry-based models. Hospitals were divided into quartiles and risk-adjusted outcomes of AIS cases were compared across the hospital quartile to confirm volume-outcome relationship (VOR) in ERT. Spline regression was performed to determine the volume threshold. Results: The mean AIS volume was 14.8 cases per hospital per year and the unadjusted means of outcome variables were mortality 11.6%, readmission 4.6%, and ICH rate 8.6%. The VOR was observed in the risk-adjusted 30-day mortality rate across all quartile groups, and in the ICH rate between the first and fourth quartiles ( p < 0.05). Volume threshold was 24 cases per year, which was estimated by examining the relative effect on the adjusted odds of outcome for an increase in hospital volume by 10 cases/year for a hospital of a given size. Conclusions: We found an association between hospital volume and outcomes, and we identified the volume threshold in ERT. Policies to ensure the implementation of the AIS volume threshold for hospitals performing ERT is needed.