An ICD(Implantable Cardioverter is a battery-powered device placed under the skin that keeps track of your heart rate. Thin wires connect the ICD to your heart. If an abnormal fast heart rhythm is detected the device will deliver an electric shock to restore a normal heartbeat.
Single-Chamber ICD has only one wire (pacing lead) placed into a chamber of the heart. It is the lower chamber, or ventricle.Source: © Heart Rhythm Society