Hello, I'm an expert in emergency medical equipment and procedures. I can provide you with accurate information regarding defibrillators and their function. Defibrillators are crucial devices that are used to treat life-threatening cardiac arrhythmias, particularly ventricular fibrillation (VF) or pulseless ventricular tachycardia (VTach). When the heart is in these states, it's not effectively pumping blood throughout the body because the electrical signals that control the heartbeat are chaotic. A defibrillator works by delivering an electric shock to the heart, which can reset the heart's electrical activity and allow it to reestablish a normal rhythm. It's important to note that defibrillators do not "restart" the heart in the sense of initiating a heartbeat from a completely stopped state. Instead, they are used when the heart is in a dangerous rhythm that prevents it from pumping blood effectively. For a heart that has completely stopped beating (asystole), cardiopulmonary resuscitation (CPR) and other advanced life support measures are necessary. read more >>

This is not normal medical practice, as the heart cannot be restarted by the defibrillator itself. Only the cardiac arrest rhythms ventricular fibrillation and pulseless ventricular tachycardia are normally defibrillated.read more >>