Health Library

Categories > Heart Health > Heart disease: Prevention

Restoring rhythm—automatically

You’ve seen TV doctors go to work countless times, shocking a cardiac arrest patient’s heart back to life with a defibrillator (a large, paddle-like device). These days, more and more heart patients are benefiting from a personal, battery-powered version of the instrument, called an implantable cardiac defibrillator (ICD).

Beneath the surface

Unlike traditional defibrillators, ICDs do their work beneath the surface. Soap-bar-size devices, ICDs are implanted in a pouch beneath the skin of the chest or abdomen. They’re connected to insulated wires placed either against the inner heart wall or near the heart.

A shocking system

ICDs automatically administer an electric shock to the heart whenever they sense an arrhythmia—a rapid, abnormal heartbeat. The shock interrupts the abnormal rhythm and restores a regular heartbeat.

The kind of electric therapy an ICD delivers depends on what the doctor programs the device to do. Some shocks are so subtle as to be unfelt or to be experienced only as a mild fluttering in the chest. Other electric impulses may feel like a mildly uncomfortable thump.

High-energy defibrillation, the kind of electric shock that is needed to stop a very fast and irregular arrhythmia, is more like a kick in the chest. This intense sensation lasts for only a second. While some patients say they are reassured to feel the shock and know the device has worked effectively, others find the experience upsetting.

Communicating with ICDs

A programmer/recorder/monitor (PRM) is used outside the body to communicate with the implanted device via radio waves. The doctor will use PRM initially to program and test the implanted device and perhaps reprogram the ICD if the heart condition changes. When a patient comes in for a checkup, the PRM also is used to read the information stored in the ICD’s memory—a record of all the activity generated since the last visit.

Who needs an ICD?

Experts agree that ICDs can help patients who are at the highest risk of sudden cardiac death—those who have already survived at least one heart attack and have recurring arrhythmia that does not respond to medication. New studies, however, suggest that perhaps all heart attack survivors can benefit. Ongoing research may yield more definitive answers.