What is the purpose of defibrillation?

Defibrillation is a method used when a person undergoing a cardiac arrest experiences Ventricular Fibrillation. It involves giving a minor electric shock to the patient by placing two pads, one above the right nipple and the other below the heart on the left roughly diagonal to each other.(Image provided)

Ventricular fibrillation is the disorganized contraction of heart ventricles which make the heart shake instead of pumping the blood. It's a sort of cardiac arrhythmia and happens in a lot of heart attack cases. The shock depolarizes the entire electrical conduction system of the heart and the naturally present pacemaker cell can repolarize and try to assert the normal resumption of the heartbeat

Defibrillation is the process whereby a large current is passed through the heart simultaneously. This is done so that all the uneven discharging lesions in the heart are depolarized. This causes the heart to be completely depolarized simultaneously so that a single pacemaker can take over the excitatory function of the heart.

This is often employed in ventricular or atrial fibrillation in order to stop the chaotic, disorganized, contraction of the cardiac cells to ensure the synchronous contraction of the heart as a whole. This helps to stop dangerous arrhythmias that may irreversibly damage the heart as well as the body.