How Does an Implantable Cardioverter Defibrillator Work?

An implantable cardioverter defibrillator (ICD) has wires with electrodes on the ends that connect to one or more of your heart's chambers. These wires monitor your heart rhythm. They also deliver high- or low-energy electrical pulses to the heart when it beats abnormally.

Single-chamber ICDs have wires that connect to one or both of your ventricles. These ICDs correct faulty electrical signaling within the ventricles. Dual-chamber ICDs have wires that connect to both an upper heart chamber (atrium) and a ventricle. These ICDs correct faulty electrical signaling between the two chambers.

The wires on an ICD connect to a small metal box implanted in your chest or abdomen that contains a battery, pulse generator, and computer. The computer triggers the ICD's pulse generator to send electrical pulses when it detects irregular rhythms. Wires carry these pulses to the heart.

The ICD also can record the heart's electrical activity and heart rhythms. The recordings can help your doctor fine-tune the programming of your ICD so it works better to correct irregular heartbeats.

Whether you receive a single-chamber or dual-chamber ICD is based on your heart's pumping abilities, structural defects, and the type of irregular heartbeats you've had. Whichever type of ICD you receive, it will be programmed to respond to the type of irregular heart rhythm you're most likely to have.