Cardioversion is a type of procedure used to revert certain types of rapid heartbeats back to normal, most commonly used in atrial fibrillation. While in a sedated state, an electrical shock is passed through your chest wall and resets the electrical system of your heart. Usually your normal electrical system will then recover its regular synchronized pattern. It is not uncomfortable nor is it anything to be feared. Frequently patients will be placed on Coumadin, a type of blood thinner, in anticipation of a cardioversion.