Survival from cardiac arrest doubled when a bystander stepped in to apply an automated external defibrillator (AED) before emergency responders arrived, according to new research in the American Heart Association's journal Circulation. 

According to the American Heart Association, less than half (45.7 percent) of cardiac arrest victims get the immediate help they need before emergency responders arrive, in part because emergency medical services take, on average, between four and ten minutes to reach someone in cardiac arrest.

An international team of researchers looked at 49,555 out-of-hospital cardiac arrests that occurred in major U.S. and Canada cities. They analyzed a key subgroup of these arrests, those that occurred in public, were witnessed and were shockable. The researchers found that nearly 66 percent of these victims survived to hospital discharge after a shock delivered by a bystander. Their findings emphasized that bystanders make a critical difference is assisting cardiac arrest victims before emergency responders can get to the scene.

Among the study's results:

• Bystanders used an AED in 18.8 percent of these cases.
• Cardiac arrest victims who received a shock from a publicly-available AED had far greater chances of survival and being discharged from the hospital than those who did not; 66.5 percent versus 43 percent.
• Cardiac arrest victims who received a shock from a publicly-available AED that was administered by a bystander had 2.62 times higher odds of survival to hospital discharge and 2.73 times more favorable outcomes for functioning compared to victims who first received an AED shock after emergency responders arrived.
• Victims who received an AED shock from a bystander (57.1 percent) using a publicly-available device instead of having to wait for emergency responders (32.7 percent) had near normal function and better outcomes.
• Without a bystander using AED shock therapy, 70 percent of cardiac arrest patients either died or survived with impaired brain function.

One of the study's limitations is that it only examined bystander AED use without considering the combined impact of calling 9-1-1 and starting immediate CPR.

"Bystanders have the potential to save a life," Weisfeldt continued. "This should be a great incentive for public health officials and bystanders to strive to have AEDs used on all victims of cardiac arrest."

"First Aid, CPR and AED training need to become part of a larger culture of safety within workplaces," said Michael Kurz, MD, chair of the American Heart Association's Systems of Care Subcommittee and associate professor at the University of Alabama School of Medicine in the Department of Emergency Medicine. "We are certainly seeing higher public interest in this training, and our campaign calls upon decision makers in workplaces and popular public spaces such as arenas, fitness centers, hotels, and churches to place AEDs in the same locations as a fire extinguisher."

Co-authors are: Ross A. Pollack, B.S.; Siobhan P. Brown, Ph.D.; Thomas Rea, M.D., M.P.H.; Tom Aufderheide, M.D.; David Barbic, M.D.; Jason E. Buick, M.Sc.; Jim Christenson, M.D.; Ahamed H. Idris, M.D.; Jamie Jasti, B.S.; Michael Kampp, paramedic/EMS Chief; Peter Kudenchuk, M.D.; Susanne May, Ph.D.; Marc Muhr, EMT-P; Graham Nichol, M.D., M.P.H.; Joseph P. Ornato, M.D.; George Sopko, M.D., M.P.H.; Christian Vaillancourt, M.D., M.Sc.; Laurie Morrison, M.D., M.Sc.; and the ROC Investigators. Author disclosures are on the manuscript.

The study was funded by the National Heart, Lung, and Blood Institute in partnership with the National Institute of Neurological Disorders and Stroke, U.S. Army Medical Research & Material Command, The Canadian Institutes of Health Research (CIHR) - Institute of Circulatory and Respiratory Health, Defense Research and Development Canada, the Heart, Stroke Foundation of Canada, and the American Heart Association.