Abstract DP187: Changes in stroke care regionalization in California associated with evolving evidence for endovascular thrombectomy: A network analysis

Background: Since the 2015 publication of benefit for endovascular thrombectomy (EVT), hospitals have worked to transfer eligible patients to EVT-capable sites. These interhospital patient transfers lead to naturally forming clusters of hospitals that are more closely connected to one another through patient transfers than they are to other hospitals. Our objective was to investigate related changes in regionalization of stroke care reflected in the organization of stroke patient transfer networks and hospital clusters. We hypothesized that after the 2015 publication of benefits for EVT, stroke care became increasingly regionalized, with hospitals consolidated into fewer clusters centered around EVT-capable sites. Methods: We used comprehensive statewide data from California to create the network of all ischemic stroke transfers from 2010-2021. We applied network analysis strategies and used block models to identify clusters of closely connected hospitals in the transfer network. We examined changes in network characteristics over time, including the number of hospital clusters and clusters’ EVT capability (defined by presence of a hospital performing at least 2 EVT procedures in a given year). Results: We identified 19,244 transfers among 338 hospitals. The number of hospital clusters and the number of clusters with at least one EVT-capable hospital increased over time (Figures 1 and 2). The proportion of receiving hospitals with EVT-capability increased from 20.2% (43/213) to 34.1% (71/208) after 2015. EVT-capable hospitals consistently received more patients in transfer relative to non-capable hospitals (mean in-degree per year pre-2015: 15.1 vs. 3.3 and post-2015, 22.1 vs. 2.4 among EVT- and non-EVT-capable hospitals respectively). Within each cluster, the average proportion of patients that received EVT also increased (Figure 3). Conclusions: From 2010 to 2021, regionalization of stroke care in California reorganized, with an increase in EVT-capable hospitals and corresponding increase in hospital clusters around these hospitals. These changes were associated with increased performance of EVT among transferred ischemic stroke patients.