Explain the Ventricular Fibrillation
This is a fatal condition in which the heart beats like a bag of worms and the patient may die in a couple of hours, if the action is not taken immediately. You are already aware that the heart beats when electrical signals move through it. In case of ventricular fibrillation, the heart's electrical activity becomes disordered. When this happens, the heart's lower (pumping) chambers contract in a rapid, unsynchronized way. The ventricles "flutter" rather than beat. The heart does not pump sufficient blood to the entire body.
The patient has no pulse and the heart is quivering. It may be necessary to give a high voltage DC shock to revive the patient. You may have seen this being done when the doctor places electrodes on the chest to provide electrical shock to jump-start the dying heart.
The action of the defibrillator is based on the principle that a high voltage current throws the entire ventricular musculature into contraction miraculously and simultaneously.