An automated external defibrillator is a lightweight, portable electronic device that automatically diagnoses life-threatening cardiac arrhythmias (irregular heartbeat).
It is able to treat them through defibrillation (delivery of an electric shock to stop arrhythmia) allowing the heart to reestablish an effective rhythm.
This is usually use during or after a sudden cardiac arrest (SCA), in which the heart stops functioning abruptly.
Most SCAs result from ventricular fibrillation (VF). VF is a rapid and unsynchronized heart rhythm that originates in the heart’s lower chambers (the ventricles).
A built-in computer checks heart rhythm through adhesive electrodes. The computer calculates whether defibrillation is need. If it is, a shock button is presse on the AED.
This shock momentarily stuns the heart and stops all activity. AEDs advise a shock only for VF or pulseless ventricular tachycardia (increased heart rate without a pulse originating in the ventricles).
AEDs are safe to use by anyone. Studies show that 90% of the time AEDs cab detect arrhythmias and decide whether to deliver a shock or not.