title: Long-term changes in the incidence of out-of-hospital ventricular fibrillation.
abstract: OBJECTIVE
  To report the long-term changes in the incidence of out-of-hospital ventricular fibrillation (VF), and also to report concurrent changes in the possible explanatory factors for the change.
  
  
  METHODS
  This was a retrospective observational study. All bystander-witnessed out-of-hospital cardiac arrests (with a known initial rhythm) in Helsinki, Finland during 1.1.1994-31.12.2007 were included in the study. High (years 1994-1996) and low (2002-2004) incidence periods for VF were defined and compared.
  
  
  RESULTS
  There were 3131 bystander-witnessed out-of-hospital cardiac arrests of which 3118 (99.6%) had a known initial rhythm. During 2000-2007 the annual incidence of bystander witnessed ventricular fibrillation (VF) was 11.6 (95% CI 9.7-13.5) per 100,000 inhabitants. In 1994-1996 VF was 1.8 times more likely than in 2002-2004, after adjustment for several patient related factors and EMS related factors. Arrests with cardiac aetiology became less common, as 54.8% arrests had a cardiac cause in 1994-1996 compared to 45.2% in 2002-2004 (p<0.001). Of cardiac arrests with cardiac aetiology, 60.6% presented with VF in 1994-1996 compared to 45.7% in 2002-2004 (p<0.001). There were major changes in the possible explanatory factors during the study period.
  
  
  CONCLUSIONS
  The decline in the incidence of out-of-hospital VF seems to have ended, and the annual incidence of VF has stabilised to 11.6 (95% CI 9.7-13.5) per 100,000 inhabitants. During the period of lower incidence of VF, cardiac aetiology caused fewer arrests, and these arrests did not present with VF as often as previously.
authors: Helsinki EMS Research Group, Helsinki University Central Hospital, P.O. BOX 112, FIN-00099 Helsingin kaupunki, Finland. taneli.vayrynen@vshp.fi
authors: Taneli
authors: T
authors: Väyrynen
authors: James
authors: J
authors: Boyd
authors: Marko
authors: M
authors: Sorsa
authors: Teuvo
authors: T
authors: Määttä
authors: Markku
authors: M
authors: Kuisma
mesh_terms: D017677:Age Distribution; D016887:Cardiopulmonary Resuscitation / Q000379:methods; D004632:Emergency Medical Services; D005260:Female; D005387:Finland / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000453:epidemiology / Q000209:etiology* / Q000628:therapy; D012189:Retrospective Studies; D017678:Sex Distribution; D015996:Survival Rate / Q000639:trends; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000150:complications / Q000453:epidemiology* / Q000628:therapy