When the heart rhythm suddenly changes, rapid and possibly intermittent, the electrical signals through wires from the heart to the AED. It sees it as an emergency and sends electrical impulses back to the heart. Depending on what is wrong with the heart rhythm, the AED can be programmed for different treatments:
Low energy pacing. In such a situation, select either nothing or only a slight tremor in the chest when the AED sends weak pulses to the heart to correct minor disturbances in the heartbeat.
Cardioversion. A powerful electric shock is emitted to cope with a serious heart problem. It feels like you are getting a blow in the chest.
Defibrillation. This is the most powerful electric shock that can be made to restore normal heart rhythm. It felt painful and as though you have gotten a kick in the chest. Typically, this pain lasts only a second time, and it is rare discomfort after the shock is over.
Usually, there is enough of an electric shock to restore normal heart rhythm. Sometimes you may need two or more such shocks over a 24-hour period. Frequent shock over a short period of time is worrying, and you should subsequently immediately seek medical attention. One must then determine why it is so, if there is an error with the AED, or if there is another underlying medical explanation. Alternatively, if you need another form of treatment.