how a defibrillator works

Defibrillators work by sending an electric pulse or a shock to restore the natural heartbeat, they are commonly used for arrhythmia, and defibrillators are used for slowing down the heart rate, or a quickened heart rate.

AEDs:

Different types of defibrillators like AEDs (which are battery operated and check the heart's rhythm and send a shock to the heart to restore the normal heart rhythm) are automatic and are used for people experiencing cardiac arrest. 

They use stick pads with sensors that are attached to the chest of someone who is having a cardiac arrest, and the electrodes in the sensors check the heart rate, and a small computer in the AED checks the heart rate and administers the correct volts necessary to get the heart back to its normal heart rate.

ICDs: 

ICDs are used in surgery using the chest or stomach area, which checks for arrhythmias. Arrhythmias can interrupt the flow of blood from the heart and if it gets bad it can fully stop your heart, the ICD sends a low-powered shock, and if the low-powered shock does not work, it will send a higher-powered shock.  

The ICD can record the heart's electrical activity and heart rhythms so that it can help the healthcare provider fine-tune the programming of the device so that it gives the correct amount of electricity.

WCDs:

WDCs have sensors that attach to the skin, and they are connected by wires, that check your heart's rhythm and deliver the shock when needed, the WCD and the ICD both can do low and high-powered energy shocks, the WCD detects when you have an arrhythmia, and will send aa shock to correct the rhythm, this will take bout a minute, this device can give multiple shocks during an arrhythmia. After each  arrhythmia episode, you must replace the sensors.