How is a defibrillator used in people?

Implantable device: Implantable defibrillators are used in people who most often (not always) have poor heart function and are at risk for sudden cardiac death due to malignant heart rhythms. It's job is to sense the life threatening rhythm and provide necessary shock.

Depends: External defibrillator is placed over the left chest where the heart is and after applying gel to allow delivery of electricity without bruning the skin, energy is delivered to the chest and a shock is delivered. Aicd or implantable defibrillators due this internally through leads in the heart using lower energy.