A fast or irregular heartbeat is called an arrhythmia (ah-RITH-me-ah). Arrhythmias can prevent your heart from pumping enough blood to your body.
Cardioversion is most commonly performed in symptomatic individuals with fast, or irregular (e.g. atrial fibrillation), heart beats. Cardioversion generally can be accomplished either through the use of medication or electrical current. A standard approach, following patient sedation, involves delivering an electrical current to the heart through large stickers/pads attached to the chest wall.
Consult your physician for more detailed information about the procedure.