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Introduction: One strategy to facilitate timely endovascular revascularization therapy (ERT) is for emergency medical services (EMS) to transport patients with suspected acute ischemic stroke from large vessel occlusion (LVO) directly to comprehensive stroke centers (CSCs), a process that can potentially result in CSC over-triage and tPA delay.Hypothesis: We hypothesize that simulation modeling can identify optimal characteristics of an EMS protocol that directly transports patients with suspected LVO to CSCs.Methods: Simio (Simio LLC, Sewickely, PA) was used to develop and test a simulation model estimating tPA and ERT rates among EMS-transported patients if an EMS preferential triage policy were implemented in a large, urban EMS system with 23 primary stroke centers (PSC) and 7 CSCs. The process map included time from symptom onset to calling 911, stroke severity, accuracy of field LVO identification, scene and interfacility transport times, and time from hospital arrival to treatment. Current state estimates were obtained from the Get With the Guidelines-Stroke registry, into which the EMS system’s PSCs and CSCs report data.Results: Table 1 shows current treatment rates, theoretical maximum treatment rates (if CSC transport time = 0), and treatment and CSC transport rates in simulations varying symptom onset time as a cut-off criterion for direct transport to a CSC rather than a closer PSC. In sensitivity analysis, accuracy of field LVO identification and interfacility transfer time had the largest positive and negative effect, respectively, on the primary outcomes.Conclusions: Direct transport of patients with suspected LVO who have symptom onset greater than 2 hours prior to EMS arrival is predicted to result in high treatment rates with only a modest increase in the number of patients transported to CSCs and without delaying tPA. Accuracy of field LVO identification and interfacility transport processes may be targets for optimizing EMS stroke systems of care.