The AED is designed to deliver an electric shock to a fibrillating heart, as occurs during some forms of heart attack. In a few cases, the shock will cause the heart to revert to a more effective rhythm, buying the patient a little time to get to a hospital and be stabilized. However, the AED is not a stand-alone treatment. It is only one step in a chain of medical care involving cardio-pulmonary resuscitation, defibrillation, advanced life support with drugs and airway control, and cardiac intensive care in a hospital.