Implantable Cardioverter-Defibrillator (ICD)

Topic Overview

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 having one, 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 act as pacemakers, sending weaker shocks 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. You should completely avoid things like heavy electrical or industrial equipment.

The table below lists 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.

Safe and unsafe electrical or magnetic sources

Sources that are SAFE to use

Sources to AVOID

Entertainment AM/FM radios Televisions, video cassette recorders (VCRs), CD players, DVD players, and their remote controls Household Motor vehicles (unless your doctor has restricted your driving) Bathroom appliances (such as electric razors, curling irons, hair dryers) Conventional ovens Electric tools (such as drills, table saws) Garage door openers Heating pads, electric blankets Kitchen appliances (such as toasters, blenders, electric can openers, refrigerators) Lawn and garden equipment (such as mowers, leaf blowers) Microwave ovens Phones (landline phones including cordless models.) Washing machines and dryers Medical and dental Dental procedures Most medical tests (X-ray, CT scan, mammogram) Office Computers Copy machines Fax machines Printers

Keep at least 6 in. (15 cm) away from your pacemaker or ICD: Cellular phones Keep at least 12 in. (30.5 cm) away from your pacemaker or ICD: Arc welders Battery-powered cordless power tools Industrial power generators Magnets Magnetic wands used at airports Stereo speakers Avoid completely: CB or ham radios High-voltage power lines [keep at least 25 ft (7.6 m) away]. Large magnets MRI machines Radio transmitters (including those used in toys)

Driving is something else you need to think about if you have an ICD. Talk to your doctor about whether you should restrict your driving. Your doctor will check your medical history as well as your risk of having another arrhythmia that could make driving unsafe. To help doctors with this decision, the American Heart Association and Heart Rhythm Society recommend the following driving restrictions:^{1, 2}

• 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.

	Go to top of page	Go to next section
Author:	Robin Parks, MS	Last Updated: September 1, 2006
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine Stephen Fort, MD, MRCP, FRCPC - Interventional Cardiology
© 1995-2008 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.