Implantable Cardioverter Defibrillator - (ICD's) are small battery-powered devices that are used to analyze and treat abnormal heart rhythms. The ICD is placed under the skin and where up to three wires are placed into a vein under the collarbone through which they travel to the heart. If an abnormal heart rhythm is detected the device will deliver an electric shock to restore a normal heartbeat if your hart is beating chaotically and much too fast. The ICD will then shock your heart back to a normal rhythm if you develop a rapid, dangerous heartbeat. These devices also contain pacemakers that treat slow heart rhythms.