Placing automated external defibrillators (AEDs) in communities is associated with nearly a doubling of survival after out-of-hospital cardiac arrest and the results reinforce the importance of strategically expanding community-based AED programs, according to a study in the April 20 issue of the Journal of the American College of Cardiology.
Myron L. Weisfeldt, MD, chairman of the department of medicine at Johns Hopkins University in Baltimore, and colleagues from various institutions performed a population-based cohort study of persons with nontraumatic out-of-hospital cardiac arrest (OHCA) before emergency medical system (EMS) arrival at Resuscitation Outcomes Consortium sites between December 2005 and May 2007.
Of 13,769 OHCAs, 32 percent received bystander CPR but had no AED applied before EMS arrival, and 2.1 percent had an AED applied before EMS arrival. The AED was applied by healthcare workers (32 percent), lay volunteers (35 percent), police (26 percent), or unknown (7 percent).
Overall survival to hospital discharge was 7 percent. Survival was 9 percent with bystander CPR but no AED, 24 percent AED application, and 38 percent with AED shock delivered.
In multivariable analyses adjusting for age and sex; bystander CPR performed; location of arrest (public or private); EMS response interval; arrest witnessed; initial shockable or not shockable rhythm; and study site, AED application was associated with greater likelihood of survival. Extrapolating this data to the population of the U.S. and Canada, AED application by bystanders seems to save 474 lives per year.
"This observational study, drawn from a large set of heterogeneous communities, provides strong evidence that AED application before EMS arrival is associated with improved survival after OHCA," the authors concluded.
Weisfeldt and colleagues suggested that the results underscore the "critical importance of early defibrillation and continue to encourage innovative approaches to achieve this critical link in the chain of survival."
They said that such innovative approaches may include implanted monitors with electronic alert to a bystander and the EMS system. Another strategy includes mandatory registration of all public access defibrillators with local EMS dispatch. The dispatcher could coach one person to start CPR and another bystander to retrieve the closest AED. Also, placement of all AEDs may be guided by a model that considers health risk, population density, and rate of cardiac arrest in similar buildings.