Implantable Cardioverter Defibrillators (ICDs)

What is an implantable cardioverter defibrillator (ICD)?

The implantable cardioverter defibrillator (ICD) is a device made to shock the heart back into a normal rhythm to prevent sudden death. It is small enough (2 to 3 inches across) to be put under the skin of the chest.

How does it work?

The ICD system consists of:

a pulse generator that can send a powerful shock to the heart
electrodes to sense the rhythm of the heart and to carry the shock to the heart muscle
batteries that last 5 to 9 years depending on how often it has to give a shock
an electronic logic circuit to tell the ICD when to discharge
a pacemaker.

If the heart is beating normally, the ICD does nothing. When an abnormal fast heart rate, known as ventricular tachycardia, is detected, the ICD will first try to control the heart rhythm. If this doesn't work, or the rhythm gets worse (ventricular fibrillation) the ICD sends electric shock signals to the heart. The electric shock changes the abnormal rhythm to a normal rhythm. The device is put under the skin in the chest, with wires that connect it to the heart.

When is it used?

ICDs may be life-saving for people who have had some types of fast heart rhythm (arrhythmias) that can cause sudden death. They may also be used for people who are at high risk of having fast heart rhythms. Most of these people have had a heart attack or have an problem in the heart muscle.

What are the risks and benefits?

There is risk with every treatment or procedure. Talk to your provider about how the risks apply to you. Once the ICD is put in, you will need regular checkups to make sure the device is working right and how much power is left in the batteries.

The most common problem with the device is that it sometimes gives shocks when you do not need them. You can feel each shock, even though it lasts only a very short time. Your provider should be notified of every shock you feel. When the batteries have run down, the tool must be replaced. Replacement of the tool is a short procedure, because the wires stay in place.

The ICD does not fix existing heart problems, but lowers the risk of dying from an abnormal heart rhythm. For many people, the device provides peace of mind and can help people live longer.

What happens after ICD implantation?

Recovery time after surgery to put one of the ICD units in is quite short. You will usually stay overnight in the hospital. When you return home, you should take it easy. You will probably tire easily. Avoid sudden, jerky movements with your arms, or stretching or reaching over your head. Your provider will tell you when you can return to your usual activities. Follow your provider's advice about medicine, diet, and exercise.

How can I take care of myself when I have an ICD?

When you have an ICD, you need to be aware of things that may interfere with ICDs:

Keep your cell phone at least 6 inches away from your ICD. When your phone is turned on but not in use, do not carry it in your breast pocket.
ICDs may not work properly near power-generating equipment, arc welding equipment, and powerful magnets. For example, magnetic resonance imaging (MRI) uses a powerful magnet to produce images of internal organs. The magnet can interrupt the pacing of ICDs.
X-rays generally appear to have no effect on ICDs, but radiation used to treat cancer may damage the circuits of the ICD.

Tell all your health care providers and dentists that you have a ICD.

Devices that generally do not damage ICDs include:

electric drills
electric blankets and heating pads
electric shavers
metal detectors
microwave ovens
televisions and remote controls.

Passing through the metal detector at airports will not damage a ICD, but the metal in it may sound the alarm. Be sure to carry an ID card with you that says you have an ICD.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.

HIA File CRD3633F.HTM Release 9.0/2006