While an AED is a type of defibrillator, it is by no means the only type. Internal and external manual defibrillators, semi-automated external defibrillators, implantable cardioverter defibrillator, and wearable cardiac defibrillators are used to treat different types of cardiac conditions in a hospital setting. Manual defibrillators have capabilities that automated models do not. From delivering pulses of electricity to the heart to stimulate contraction of the heart to converting arrhythmia to a normal heartbeat, manual defibrillators are designed for use by medical personnel who are trained to detect different heart problems and treat them appropriately. In some cases where an AED was first used to treat a person experiencing sudden cardiac arrest, a manual defibrillator later is used to treat a patient.