title: Outcome after out-of-hospital cardiac arrest witnessed by EMS: changes over time and factors of importance for outcome in Sweden.
abstract: BACKGROUND
  Among 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.
  
  
  OBJECTIVE
  To evaluate outcome after EMS-witnessed OHCA in a 20-year perspective in Sweden, with the emphasis on changes over time and factors of importance.
  
  
  METHODS
  All patients included in the Swedish Cardiac Arrest Register from 1990 to 2009 were included.
  
  
  RESULTS
  There 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.
  
  
  CONCLUSIONS
  In 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.
authors.affiliation: University of Borås, School of health sciences, SE-501 90 Borås, Sweden.
authors.forename: Christer
authors.initials: C
authors.lastname: Axelsson
authors.forename: Andreas
authors.initials: A
authors.lastname: Claesson
authors.forename: Johan
authors.initials: J
authors.lastname: Engdahl
authors.forename: Johan
authors.initials: J
authors.lastname: Herlitz
authors.forename: Jacob
authors.initials: J
authors.lastname: Hollenberg
authors.forename: Jonny
authors.initials: J
authors.lastname: Lindqvist
authors.forename: Mårten
authors.initials: M
authors.lastname: Rosenqvist
authors.forename: Leif
authors.initials: L
authors.lastname: Svensson
mesh_terms: D000368:Aged; D004632:Emergency Medical Services; D005260:Female; D006801:Humans; D008297:Male; D058687:Out-of-Hospital Cardiac Arrest / Q000628:therapy*; D013548:Sweden; D013997:Time Factors; D016896:Treatment Outcome