Implantable Cardioverter-Defibrillator (ICD)

An implantable cardioverter-defibrillator (ICD), also known as an automatic implantable cardioverter-defibrillator (AICD), is a small device that doctors use to watch for and fix life-threatening abnormal heart rhythms. The doctor surgically implants the defibrillator under the skin, usually below the left collarbone. A wire threaded through a large vein connects the device to the heart.

If you have had a serious episode of an abnormally fast heart rhythm or are at high risk for sudden cardiac death, you may need an ICD.

If you have coronary artery disease, heart failure, or a problem with the structure or electrical system of the heart, you may be at risk for an abnormal heart rhythm.

How does an ICD work?

An ICD continuously monitors your heart. If it detects a life-threatening rapid heart rhythm, it sends an electric shock to your heart to restore a normal rhythm. The device then goes back to its monitoring mode.

After the shock, your heart may beat very slowly for several minutes. So ICDs also contains pacemakers, sending electrical impulses that pace the heart if the rate falls below a certain preset level.

Your doctor sets both the rate at which a shock will occur and the level of shock needed to convert to a normal rate and rhythm. If the first shock does not reset your heart rhythm, the device will send progressively stronger shocks until the heart converts to a normal rate.

Although an ICD effectively treats life-threatening episodes of abnormal heart rhythms, it does not prevent them. You will also need to take a medicine to prevent or at least decrease how often you have abnormal heart rhythms so that you are not getting too many shocks.

Living with an ICD

You may feel worried by the possibility of being shocked. The shock itself can be uncomfortable— it may feel like you are being kicked in the chest. You may pass out before the device fires, and you likely won’t remember the shock. Be reassured though, that the shock is life-saving.

Strong electric or magnetic fields can interfere with the ICD. Most electrical equipment and household appliances create very weak magnetic fields and do not interfere with ICDs. So you can safely use most household and office equipment. And you can usually avoid electrical interference from magnetic or electrical sources by keeping certain things a few inches away from your pacemaker or ICD.

The list below shows electrical and magnetic sources that are safe and sources that you should avoid. This table does not list all magnetic or electrical sources that you might use. Ask your doctor about the safety of sources not listed here.

Stay away from

  • CB or ham radios
  • High-voltage power lines.
  • Large magnets
  • MRI machines. An MRI uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body.
  • Arc welders
  • Battery-powered cordless power tools.
  • Industrial power generators
  • Magnets
  • Magnetic wands used at airports.
  • Stereo speakers

Use with caution

  • Cell phones:
    • Do not carry a cell phone in a pocket directly over the pacemaker or ICD.
    • Hold the phone to the ear on the side away from your device.
    • Keep a phone at least away from the pacemaker or ICD.
  • Keep the following devices at least away from the pacemaker or ICD:
    • Arc welders
    • Battery-powered cordless power tools
    • Industrial power generators
    • Magnets
    • Magnetic wands used at airports
    • Stereo speakers
    • Radio transmitters (including those used in toys)

Safe to use

  • Kitchen and bathroom equipment:
    • Bathroom appliances (electric razors, curling irons, and hair dryers)
    • Kitchen appliances (such as toasters, blenders, electric can openers, and refrigerators)
    • Microwave, gas, and electric ovens
  • Office equipment:
    • Computers
    • Copy machines
    • Fax machines
    • Printers
  • Other household items:
    • Electric tools (such as drills and table saws)
    • Lawn and garden equipment (such as mowers and leaf blowers)
    • Heating pads and electric blankets
    • Washing machines and dryers
    • Phones (landline phones including cordless models)
    • Remote controls
    • TVs, VCRs, CD players, DVD players

Driving is something else you need to think about if you have an ICD.

To help doctors with this decision, the American Heart Association and Heart Rhythm Society recommend the following driving restrictions:

  • If you get an ICD because you are at risk for a life-threatening arrhythmia (but have never had one), you should not drive for at least 1 week afterward to allow time to heal. After you heal, you can drive again as long as your ICD has never given you a shock and you have no symptoms of an arrhythmia. But keep in mind that an arrhythmia could cause you to pass out (lose consciousness).
  • If you get an ICD because you have already had a life-threatening arrhythmia, you should wait at least 6 months before you drive again.
  • If you have an ICD that has given you a shock for an arrhythmia, you should wait at least 6 months before you drive again.

It is important to keep your regular follow-up appointments with your doctor. He or she will check the device to see whether it has delivered any shocks since your last visit. This will help determine whether your medicines need to be adjusted. During your follow-up visits, your doctor will also check the battery and replace it at regular intervals.