Ask the doctor
Q. Is there any danger to using an AED to shock a person’s heart if he or she doesn’t actually need it?
A. An AED (automated external defibrillator) is designed to deliver an electric shock through the chest to the heart. Using it on a person who experiences cardiac arrest—a sudden loss of heart function—may save the person’s life. But even if the problem isn’t cardiac arrest, using the AED is very unlikely to cause harm.
AEDs provide step-by-step visual and voice prompts to allow even untrained bystanders to use the device correctly, and include a safety feature that prevents unneeded shocks.
Most often, cardiac arrest is caused by ventricular fibrillation, which occurs when the heart’s lower chambers (ventricles) quiver very rapidly and irregularly. Without a pulse or blood pressure, the person collapses and loses consciousness.
An AED includes two sticky pads with sensors (electrodes) that you place on either side of the unconscious person’s bare chest. These electrodes detect the heart’s rhythm, which a computer then analyzes to determine if a shock is needed. Contrary to what some people assume, the shock doesn’t “restart” the heart. Instead, it works by restoring the heart’s normal rhythm.
If you see a person suddenly collapse (or find someone unconscious), shout or shake the person to confirm that he or she is unresponsive. Call 911 or have someone else call. One person should do chest compressions (cardiopulmonary resuscitation) while someone else gets the AED. These devices are found in many public places, including airports, sports arenas, malls, and fitness centers.
— Deepak Bhatt, MD, MPH
Editor in Chief, Harvard Heart Letter