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.

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.

Other Places To Get Help

Organizations

Related Information

• Atrial Fibrillation
• Dilated Cardiomyopathy
• Heart Attack and Unstable Angina
• Heart Failure
• Hypertrophic Cardiomyopathy
• Restrictive Cardiomyopathy

References

Citations

1. Epstein AE, et al. (1996). Personal and public safety issues related to arrhythmias that may affect consciousness: Implications for regulation and physician recommendations. A medical/scientific statement from the American Heart Association and the North American Society of Pacing and Electrophysiology. Circulation, 94(5): 1147–1166.

2. Epstein AE, et al. (2007). Addendum to Personal and public safety issues related to arrhythmias that may affect consciousness: Implications for regulation and physician recommendations: A medical/scientific statement from the American Heart Association and the North American Society of Pacing and Electrophysiology. Public safety issues in patients with implantable defibrillators. A scientific statement from the American Heart Association and the Heart Rhythm Society. Circulation, 115(9): 1170–1176.

Credits