Ventricular fibrillation in King County, Washington: a 30-year perspective.

AIM: We determined the effect of four major program changes over a 30-year period on survival from witnessed cardiac arrest (CA) with ventricular fibrillation (VF) as the rhythm causing collapse.
METHODS: We conducted an investigation of emergency medical services (EMS)-treated CA occurring between 1978 and 2007. Data were obtained from a registry maintained by the King County Emergency Medical Services Division. Using Utstein style definitions, we measured changes in patient survival in light of four programs that were implemented during the span of the study: defibrillation by emergency medical technicians (EMTs), dispatcher-assisted cardiopulmonary resuscitation (CPR), public access defibrillation, and a CPR-defibrillation protocol that replaced delivery of three sequential shocks with administration of one shock followed by 2 min of CPR.
RESULTS: Overall survival from witnessed VF during the study period was 34%. While demographic characteristics of patients in CA remained constant, we observed greater rates of survival in the years following the program changes, 1983-2006, compared to survival in the period before the changes, 1977-1982. The greatest increase in survival occurred following the CPR-defibrillation protocol change in 2005.
CONCLUSION: Despite adverse temporal trends, the four program changes appear to have contributed to increasing survival rates from out-of-hospital cardiac arrests in King County.