Cardiac arrests witnessed by EMS personnel in a multitiered system: Epidemiology and outcome

The purpose of the study was to determine the epidemiology and the etiology of cardiac arrests witnessed by emergency medical services (EMS) personnel and the survival from resuscitation according to the Utstein style. Consecutive prehospital cardiac arrests witnessed by EMS personnel in the Helsinki City EMS system between January 1, 1994 and December 31, 1995 were included in this prospective cohort study. A total of 809 cardiac arrests were registered during the study period, 108 (13.3%) of which were EMS-witnessed. The incidence of EMS-witnessed cardiac arrests was 1.8 per 1,000 urgent calls per year. Resuscitation was attempted in 94 patients, 45 of whom (47.9%) were hospitalized alive and 15 of whom (16.0%) were discharged. Fourteen of the survivors were discharged with overall performance category I or II. Cardiac etiology was verified in 60 (55.6%) cases. In multivariate analysis, initial rhythm of ventricular fibrillation and cardiac etiology remained independent factors of survival. These results indicate that overall survival rates in EMS-witnessed cardiac arrests have remained low but those who survive are discharged without major neurological sequelae. Noncardiac etiology accounts for 45% of cases and seems to be a major determinant of low overall survival rates.