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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.

An example of a life-threatening heart rhythm is ventricular tachycardia.

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.

**Safety guidelines for ICDs**
Stay away from	CB or ham radios High-voltage power lines. Stay at least 25ft away. 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 6in. away from the pacemaker or ICD. Keep the following devices at least 12in. 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 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 Office equipment: Computers Copy machines Fax machines Printers

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WebMD Medical Reference from Healthwise

Last Updated: August 25, 2008

This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.