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. Copyright © 2006 McKesson Corporation and/or one of its subdiaries. All Rights Reserved.
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