INTRODUCTION: Cardiac arrest in the emergency department (ED) is a rare event. Prior studies have used dedicated cardiac arrest registries, but few have leveraged "big data" from electronic healthcare vendors to analyze trends in the care of patients excluded from registries. METHODS: This was a retrospective cohort study of adult patients in the ED with cardiac arrest from Epic Cosmos, a database with 277 million patients. Patients with ICD-10 codes corresponding to cardiac arrest in the ED were included. Outcomes included the incidence of cardiac arrest, mortality, code length, and extracorporeal membrane oxygenation (ECMO). Data were compared using odds ratio with 95 % confidence intervals (CI). RESULTS: Among 196,834,283 ED visits from 1/1/2016 to 12/31/2023, there were 429,917 (0.22 %) cardiac arrests and 197,233 (45.88 %) patients who died in the ED. The incidence of cardiac arrest (0.26 %) and death in the ED (55.70 %) peaked in 2020. Cardiac arrest was more common in male and older patients, between 00:00-05:59, on weekends, and in the South (p <
0.001). The median code length was 10-20 min. Only 0.29 % of cardiac arrest patients received ECMO. Compared to 2016, the odds of a code length >
90 min and ECMO in 2023 were 1.43 (95 % CI 1.32-1.54) and 3.58 (95 % CI 2.41-5.31) times greater, respectively. CONCLUSION: Although cardiac arrest in the ED is a rare event, almost half of patients die in the ED. The use of ECMO after cardiac arrest is increasing but remains low. Further research is needed to mitigate these differences in care.