A defibrillator, also known as an implantable cardioverter defibrillator (ICD), is a small electronic device implanted in the chest to monitor heart rhythms continuously.
When the heart begins to beat dangerously and abnormally fast — a condition called arrhythmia — a defibrillator can send electrical impulses that shock the heart, causing it to beat in a normal rhythm again. A defibrillator is always on standby, ready to take lifesaving action when necessary.
Defibrillators are most commonly recommended if you have a hyperactive or irregular heartbeat in a ventricle, a blood-pumping chamber of the heart. When a ventricle pumps too quickly, the condition is called ventricular tachycardia. When a ventricle twitches or flutters erratically, the condition is called ventricular fibrillation. Either condition can cause sudden death.
Defibrillator implant is recommended for patients who have experienced irregular, fast heartbeat in the past that results in fainting or sudden cardiac arrest.
A defibrillator is programmed by an electrophysiologist, a cardiac physician who specializes in heart rhythms. The device can be set to restore normal heart rhythm in several ways:
- Anti-tachycardia pacing (ATP), or "overdrive pacing," is a sequence of electrical impulses delivered to the heart when it beats dangerously fast (tachycardia).
- Cardioversion is a low-energy shock delivered at the same time as a heart beat after a sequence of ATP impulses fails to restore normal heart rate.
- Bradycardia pacing is needed when the heart beats too slowly (bradycardia). Electrical impulses will speed the heart rate.
- Defibrillation will stop a severely abnormal heart rhythm by delivering a high-energy shock.
Newer defibrillator models also will record the date and time of a ventricular tachycardia or fibrillation event, as well as note the electrical therapy provided to the heart.
Defibrillator Implant Surgery
Defibrillators usually are implanted through small incisions in the skin, near the collarbone. You receive a mild sedative, but you're kept awake; a local anesthetic is used. An electrophysiologist will perform the procedure.
Using a fluoroscopy machine that creates moving X-rays to visualize the chest's interior, an electrophysiologist guides the defibrillator leads through the incisions, into veins, until they reach the heart. There, the tip of each lead is attached to the heart muscle. Next, the leads are connected to the device's pulse generator, which is then placed in a pocket just beneath the skin in the upper chest.
With the defibrillator in place, the electrophysiologist will perform a series of tests to ensure that device is working properly. An artificially fast heart rhythm might be programmed, simply to ensure that the leads are properly monitoring heart beats, and the pulse generator is sending the appropriate signals to stop the abnormal heart beat. Afterward, the device is programmed to meet the patient's needs.
After Defibrillator Implantation
Following surgery, you need to visit the electrophysiologist for routine follow-up visits. The first appointment is scheduled within six weeks of the device implantation.
During each visit, the defibrillator will be checked by a programmer device that will indicate:
- Whether the defibrillator is working properly.
- Current settings.
- Whether it has delivered corrective signals to the heart.
- How much energy remains in its battery.
The defibrillator's leads also may be checked. Programming adjustments can be made as well.
Depending on how much electrical shock it delivers, a defibrillator's battery can last anywhere from three to eight years. When the battery's voltage runs low, a new ICD will be implanted. However, the defibrillator's leads most likely will not be replaced.
Defibrillator therapy is part of a larger treatment program that may include medications, proper nutrition, moderate physical activity and healthy lifestyle choices.
Reduced Radiation Heart Procedures
Learn more about our reduced radiation procedures for defibrillator implantation available at the John C. Lincoln Medical Center.