In some situations abnormal heart rhythms can be stopped by resetting the heart’s electrical system. This is a bit like rebooting your computer. This is done by delivering a short shock of electricity across the chest.
Prior to the procedure the patient is sedated heavily so that no pain is felt. Large electrodes are placed on the chest and then an electrical charge is delivered for less than a second. This usually resets the heart rhythm to normal and drugs are then used to maintain normal rhythm. This is usually performed for atrial fibrillation or atrial flutter but most rhythms can be reset in this manner.