If a heart is fibrillating – that is, rapidly beating in a very shallow way almost like vibration – it cannot pump blood adequately around the body (see VENTRICULAR FIBRILLATION). Applying an electric shock via paddles applied to the chest wall causes simultaneous electrical depolarisation of all the cardiac cells, and may allow the heart's natural pacemaker to re-establish a normal rhythm. One paddle is placed below the right clavicle and the other over the cardiac apex. Care must be taken that no one is in contact with the patient or the bed when the shock is given, in order to avoid electrocution.