• A subcutaneous implantable cardioverter-defibrillator (ICD) is a small, battery-powered device. It fixes serious changes in your heartbeat. ICDs are indicated in persons who have had or are at high risk of having a life-threatening cardiac rhythm.
• The ICD is linked to a wire and is implanted beneath the skin of the chest (called a lead). The lead is placed under the skin so that it lies near your heart.
•  The ICD delivers an electric shock to the heart if it detects a life-threatening cardiac rhythm. This restores a normal rhythm.

Reference: Learning About an ICD (Implantable Cardioverter-Defibrillator). (n.d.). Retrieved from https://healthy.kaiserpermanente.org/health-wellness/health-encyclopedia/he.learning-about-an-icd-implantable-cardioverter-defibrillator.uh3434