Implantable Cardioverter Defibrillator

An implantable cardioverter defibrillator is used in patients at risk for recurrent, sustained ventricular tachycardia or fibrillation.

The device is connected to leads positioned inside the heart or on its surface. These leads are used to deliver electrical shocks, sense the cardiac rhythm and sometimes pace the heart, as needed. The various leads are tunnelled to a pulse generator, which is implanted in a pouch beneath the skin of the chest or abdomen. These generators are typically a little larger than a wallet and have electronics that automatically monitor and treat heart rhythms recognized as abnormal. Newer devices are smaller and have simpler lead systems. They can be installed through blood vessels, eliminating the need for open chest surgery.

When an implantable cardioverter defibrillator detects ventricular tachycardia or fibrillation, it shocks the heart to restore the normal rhythm. New devices also provide overdrive pacing to electrically convert a sustained ventricular tachycardia, and "backup" pacing if bradycardia occurs. They also offer a host of other sophisticated functions (such as storage of detected arrhythmic events and the ability to do "noninvasive" electrophysiologic testing).

Implantable cardioverter defibrillators have been very useful in preventing sudden death in patients with known, sustained ventricular tachycardia or fibrillation. Studies are now being done to find out how best to use them and whether they may have a role in preventing cardiac arrest in high-risk patients who haven't had, but are at risk for, life-threatening ventricular arrhythmias.

According to the American Heart Association Heart and Stroke Statistical Update, in 1998 (the most recent statistics available) there were 26,000 ICD procedures.

The implantable cardioverter defibrillator (ICD) is a device used to treat dangerously fast heart rates that occur in the lower chambers of the heart (the main pumping chambers). The ICD system looks much like a pacemaker. The device is implanted under the skin and attached to one or more leads, which are placed in or on the heart muscle.
Illustration: ICD implantation. Image of implantable cardioverter defibrillator (ICD) implanted in heart. The implantable cardioverter defibrillator (ICD) detects arrhythmias (both bradyarrhythmia and tachyarrhythmia) and delivers electrical therapy (pacing pulses or defibrillation therapy) as necessary. When not needed, the ICD merely monitors the heart without delivering any electrical energy.

The ICD detects both bradyarrhythmia (slow heart rates) and tachyarrhythmia (fast heart rates) and delivers electrical therapy to treat these rhythm disorders and restore normal rate and rhythm to the heart. Learn more about normal rhythm and arrhythmias.

ICD therapy is often prescribed for patients who have experienced at least one episode of ventricular tachycardia or ventricular fibrillation, previous cardiac arrest, or drug therapy that was ineffective in controlling the tachyarrhythmia or that caused severe side effects. Though you may feel anxious about receiving an ICD, be assured that you are joining hundreds of thousands of people who now enjoy more normal and active lifestyles because of their ICDs.

The first step in preparing for ICD implantation is for you to become informed and comfortable with what will occur. This information is provided as an overview. Ask your physician about any specific questions you have.