Outcome after out-of-hospital cardiac arrest witnessed by EMS: Changes over time and factors of importance for outcome in Sweden

Abstract

BackgroundAmong patients who survive after out-of-hospital cardiac arrest (OHCA), a large proportion are recruited from cases witnessed by the Emergency Medical Service (EMS), since the conditions for success are most optimal in this subset. AimTo evaluate outcome after EMS-witnessed OHCA in a 20-year perspective in Sweden, with the emphasis on changes over time and factors of importance. MethodsAll patients included in the Swedish Cardiac Arrest Register from 1990 to 2009 were included. ResultsThere were 48,349 patients and 13.5% of them were EMS witnessed. There was a successive increase in EMS-witnessed OHCA from 8.5% in 1992 to 16.9% in 2009 (p for trend<0.0001). Among EMS-witnessed OHCA, the survival to one month increased from 13.9% in 1992 to 21.8% in 2009 (p for trend<0.0001). Among EMS-witnessed OHCA, 51% were found in ventricular fibrillation, which was higher than in bystander-witnessed OHCA, despite a lower proportion with a presumed cardiac aetiology in the EMS-witnessed group.Among EMS-witnessed OHCA overall, 16.0% survived to one month, which was significantly higher than among bystander-witnessed OHCA.Independent predictors of a favourable outcome were: (1) initial rhythm ventricular fibrillation; (2) cardiac aetiology; (3) OHCA outside home and (4) decreasing age. ConclusionIn Sweden, in a 20-year perspective, there was a successive increase in the proportion of EMS-witnessed OHCA. Among these patients, survival to one month increased over time. EMS-witnessed OHCA had a higher survival than bystander-witnessed OHCA. Independent predictors of an increased chance of survival were initial rhythm, aetiology, place and age.