An implantable cardiac defibrillator (ICD) is a small battery-powered device that can be implanted into the chest of a person who is at risk of sudden cardiac arrest because of an abnormally fast heart rate, also known as tachycardia. The device monitors the heart rhythm at all times and is designed to shock the heart back to a normal heart rate whenever it detects a dangerously abnormal rhythm. Older models required open-chest surgery for implantation, but newer models are much smaller and can be installed under the skin, with an insulated wire that goes to the heart.
Doctors often recommend an implantable cardiac defibrillator for patients who have a history of tachycardia or who are at risk for having it. An implantable cardiac defibrillator works by monitoring the heart through electrode wires that are place either inside or on the surface of the heart. Whenever the monitor detects a life-threatening heart rhythm, it sends a shock to the heart to slow it down to a more normal pace. Sometimes this causes the heart to beat abnormally slowly for a few minutes. When this happens, the ICD acts as a temporary artificial pacemaker.
The implantation usually requires a hospital stay, during which the doctor will program the device according to the patients individual needs. During regular check-ups, the doctor will test the battery, which should last about seven years. When necessary, the battery can be replaced during an outpatient surgical procedure. After the implantation, patients are advised to limit activities for a few weeks.
People who have an implantable cardiac defibrillator are advised to stay away from large magnets, high voltage power lines, magnetic resonance imaging (MRI) machines and battery-powered cordless tools. The magnetic and electric fields from these devices can interfere with the implantable cardiac defibrillator and disrupt monitoring. Common household appliances, office equipment and lawn equipment can all be used safely around an ICD.
When tachycardia is detected and the implantable cardiac defibrillator shocks the heart, patients might experience a sensation that feels like being kicked in the chest. Although this can be frightening, it is reassuring to know that the ICD has just delivered a life-saving shock. When the ICD is acting as a pacemaker, patients might experience a fluttering in the chest if they feel anything at all.