AED use doubles cardiac-arrest survival

Beefed up with the inclusion of more than 3,000 patients over an additional five months of follow-up, published results from the Resuscitation Outcomes Consortium (ROC) — first presented at the 2007 AHA meeting — clearly show that automated external defibrillators (AEDs) can improve survival from out-of-hospital cardiac arrest, even when untrained laypersons are the ones applying the life-saving device[1].

"Application of an AED in communities is associated with nearly a doubling of survival after out-of-hospital cardiac arrest," the authors, led by Dr Myron L Weisfeldt (Johns Hopkins University School of Medicine, Baltimore, MD), report in the April 20, 2010 issue of the Journal of the American College of Cardiology. "These results reinforce the importance of strategically expanding community-based AED programs."

As previously reported by heartwire, the earlier glimpse at the study results, covering 12 months, suggested that out of 10 663 people who suffered an out-of-hospital cardiac arrest, those who had AEDs applied had an unadjusted two- to threefold higher likelihood of surviving than if they had cardiopulmonary resuscitation (CPR), but no AED was used.

Now, in the published study, Weisfeldt et al report results for 13 769 out-of-hospital cardiac arrests from seven locations across the US and three in Canada. Of those, one-third (4403) received CPR from a bystander but had no AED applied before emergency services arrived, while just 2.1% (289 subjects) had an AED applied.
Just 7% of patients who received CPR survived to hospital discharge, as compared with 24% of patients who had the AED applied. The proportion of survivors increased to 38% if an AED was applied and a shock was delivered.
Weisfeldt and colleagues also controlled for a wide range of potential confounders, including age, location of arrest, delay to emergency response, and whether the arrest was witnessed, among other factors. Even taking all these things into account, they concluded, use of an AED increased survival by 75% (odds ratio 1.75; 95% CI 1.23–2.50).

"Extrapolating this greater survival from the ROC [emergency medical services] EMS population base (21 million) to the population of US and Canada (330 million), AED application by bystanders seems to save 474 lives per year," the authors conclude.

Of note, nonmedical "lay volunteers" constituted the largest group of people applying the AEDs (35%), followed by healthcare workers (32%) and police officers (26%). Moreover, survivors among those who had had an AED applied were more likely to have collapsed in public, rather than at home or in another private setting. While public-placement strategies for AEDs clearly have an "established role," it's also worth studying ways of optimizing "private AED deployment," they conclude.

References
1. Weisfeldt ML, Sitlani CM, Ornato JP, et al. Survival after application of automatic external defibrillators before arrival of the emergency medical system: Evaluation in the Resuscitation Outcomes Consortium population of 21 million. J Am Coll Cardiol 2010; 55:1713-1720.