Implantation of Implantable Cardioverter Defibrillator (ICD) An ICD is a small electronic device surgically implanted in the chest, just beneath the skin below the collar bone. The ICD is capable of monitoring the heart rhythm and functions to control life-threatening heart rhythm abnormalities that causes sudden cardiac arrest. When the heart is beating normally, the device remains inactive. If the heart develops a life-threatening rhythm, the ICD delivers an electrical “shock(s)” to the heart to bring the heart rhythm back to normal. Modern ICDs are unobtrusive and do not affect daily activities.