An ICD (Implantable Cardioverter-Defibrillator) monitors the heart's electrical activity constantly. It delivers an electric shock to the heart when it identifies a potentially fatal irregular cardiac rhythm, such as ventricular tachycardia or ventricular fibrillation. This shock, termed defibrillation, is intended to reset the heart's rhythm and return it to a normal, stable pattern. This quick intervention can save lives by preventing abrupt cardiac arrest. Pacing functions are also available in some ICDs to address slow or irregular cardiac beats.