If a current of 50 mA passes through the heart, it can cause cardiac arrest.
The heart is also a muscle, which beats to pump blood through the body. The rhythm of our heartbeat is controlled by electric impulses—it is these impulses that are monitored by an electrocardiogram. If a current from outside the body passes through the heart, it can mask these impulses and disturb the heart’s rhythm. This irregular heartbeat is called arrhythmia and can even manifest as a total disorganization of the rhythm, known as ventricular fibrillation.
When ventricular fibrillation occurs, the heart stops pumping and the blood stops circulating. The victim rapidly loses consciousness and dies if a healthy heartbeat is not restored with a device called a defibrillator.
The arrhythmia can occur at the time of the shock or in the hours following the electric shock.