Shockable arrhythmias more common after cardiac arrest in public vs. home

Weisfeldt M. N Engl J Med. 2011; 364:313-321.

Issue: March 2011

According to new study results, the presence of ventricular fibrillation or pulseless ventricular tachycardia as the first recorded rhythm after out-of-hospital cardiac arrest is much greater after cardic arrests that occur in public than those occuring at home.

“Thirty years ago, 70% of such arrests were characterized by initial ventricular fibrillation or pulseless ventricular tachycardia; today, the incidence is 23%,” the researchers said in the study. “This decline is of substantial importance for public health, since more than 300,000 Americans have an out-of-hospital arrest each year, with an estimated survival rate of 7.9% nationally, and the majority of survivors are in the subgroup of persons whose initial rhythm is ventricular fibrillation or pulseless ventricular tachycardia.”

The researchers prospectively tracked out-of-hospital cardiac arrests in an adult cohort from 10 North American communities. Of a total of 12,930 out-of-hospital cardiac arrests, 9,564 occurred at home and 2,042 occurred in public.

For cardiac arrests that occurred at home, the rate of ventricular fibrillation or pulseless ventricular tachycardia was 25% when EMS personnel were present, 35% when bystanders were present and 36% when a bystander applied an AED. For cardiac arrests that occurred in public, these rates were 38%, 60%, and 79%, respectively.

The significant difference in rates between home and public arrests may be explained by the fact that “the person who has a cardiac arrest in the home is typically older and more likely to have one or more chronic diseases that limit or preclude participation in activities outside the home,” according to the researchers.

They also calculated the adjusted odds ratio for initial ventricular fibrillation or pulseless ventricular tachycardia. For cardiac arrests in public vs. those occurring at home, the adjusted OR was 2.28 (95% CI, 1.96-2.66) for bystander-witnessed cardiac arrests and 4.48 (95% CI, 2.23- 8.97) for cardiac arrests in which bystanders applied AEDs. They also calculated the rate of survival to discharge as 34% for cardiac arrests in public with AEDs applied by bystanders vs. 12% for those occurring at home (adjusted OR=2.49; 95% CI, 1.03-5.99).

“Although the role of AEDs in cardiac arrests that occur in the home will probably continue to evolve, the relatively low incidence of shockable arrhythmias in this setting suggest that a treatment strategy that emphasizes prompt, bystander-delivered CPR of high quality (eg, with the assistance of a dispatcher) should be as effective in saving lives as the widespread deployment of AEDs in homes,” the researchers concluded.

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