Cardiac Arrest Survival Spikes When Bystanders Use Automated External Defibrillators

The longer it takes emergency personnel to arrive, the greater the benefit of AED use

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 (AHA) journal Circulation.

According to the AHA, of the more than 350,000 out-of-hospital cardiac arrests that occur in the U.S. each year, more than 100,000 happen outside the home. Less than half (45.7%) 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 10 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 Canadian 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% 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% 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% versus 43%.
  • 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%) using a publicly available device instead of having to wait for emergency responders (32.7%) had near-normal function and better outcomes.
  • Without a bystander using AED shock therapy, 70% of cardiac arrest patients either died or survived with impaired brain function.

“We estimate that about 1,700 lives are saved in the United States per year by bystanders using an AED,” said senior study author Myron Weisfeldt, MD. “Unfortunately, not enough Americans know to look for AEDs in public locations, nor are they are trained on how to use them despite great and effective efforts of the American Heart Association.”

According to the AHA, use of an AED is the third step in the cardiac arrest chain of survival. The first two steps in a witnessed, out-of-hospital cardiac arrest are to 1) call 9-1-1, and 2) begin immediate cardiopulmonary resuscitation (CPR).

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.

Based on the study findings, Weisfeldt and his team, including John Hopkins medical student and lead author Ross Pollack, would like to see greater distribution of AEDs, including equipping police with defibrillators, especially in regions where it takes emergency responders long to get to the patient.

“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.”

Source: AHA; February 26, 2018.