An implantable cardioverter-defibrillator (ICD) is a small battery-powered device placed in your chest to monitor your heart rhythm and detect irregular heartbeats. An ICD can deliver electric shocks via one or more wires connected to your heart to fix an abnormal heart rhythm.

Because the ICD constantly monitors for abnormal heart rhythms and instantly tries to correct them, it helps when your heart stops beating (cardiac arrest), even when you are far from the nearest hospital.