P2763Factors influencing ambulance use in patients with suspected acute coronary syndromes: a population-based geographic information system study

Abstract

Background: Despite all public awareness campaigns and guideline recommendations, the majority of patients with symptoms suggestive of acute coronary syndrome (ACS) do not use emergency medical services (EMS) to reach the emergency department (ED). Purpose(s): The aim of this study was to investigate the factors associated with EMS utilization and subsequent patient outcomes. Method(s): We used data from the metropolitan areas of Edmonton and Calgary, which are of similar size and in the same public health system (population ~3 million people). Using administrative health databases, all patients who presented to an ED in the years of 2007-2013 with main ED diagnosis of ACS, stable angina or chest pain were included. The travel distance was estimated using the geographic information system method to approximate distance between ED and patient home. The clinical endpoints of interest were the 7-day and 30-day all-cause events (composite of death, re-hospitalization, and repeat ED visit). Result(s): The cohort consisted of 50,881 patients, 15,553 (30.5%) of which were presented via EMS. The overall rate of EMS utilization was lower in Edmonton compared to Calgary (24.2% vs 36.2%; p<0.0001). Based on multivariate analysis, patients with older age, female sex, ED diagnosis of ACS and stable angina (as compared to chest pain), more comorbidities, with longer travel distance and lower household income were more likely to use EMS to reach the hospital. After adjustment for covariates and with propensity analysis/IPW, EMS use was associated with higher risk of 7-day (OR=1.17, 95% CI 1.09-1.25) and 30-day (OR=1.20, 95% CI 1.13-1.27) clinical events. Conclusion(s): Several demographic and clinical features were associated with higher EMS use including geographic variation. This has implications for the design of EMS systems, triage and early diagnosis and treatment options.