Defibrillation is a medical procedure used to restore a normal heartbeat in someone experiencing a life-threatening condition called cardiac arrest. During cardiac arrest, the heart may beat irregularly or stop altogether, preventing blood from flowing to vital organs. A device called a defibrillator delivers an electric shock to the heart, helping it reset and resume a normal rhythm. There are two main types of defibrillators: automated external defibrillators (AEDs), which can be used by bystanders in emergencies, and implantable cardioverter-defibrillators (ICDs), which are placed inside patients at risk for sudden cardiac arrest. Quick access to defibrillation can significantly increase the chances of survival.