Implantable Cardioverter Defibrillator (ICDs)

An Implantable Cardioverter Defibrillator, or ICD, is a battery-powered device that keeps track of your heartbeat, and can deliver an electrical shock that will allow ventricular muscle fibrillation to return to a normal heartbeat. The ICD can detect irregular heart rhythms, called arrhythmias In the ventricles. When the ICD detects a dangerous arrhythmia, such as ventricular fibrillation, it sends a strong electrical impulse that ‘shocks’ your heart out of the dangerous rhythm and allows normal rhythms to resume.

Defibrillation, or shock, can be the only way to stop rapid and disorganized heart rhythms before they kill. If the heart beats too quickly or the rhythm is disorganized, the chambers, or ventricles, will not have enough time to fill with blood and will not be able to pump blood to the rest of the body. This can lead to death within minutes. For people at high risk of these dangerious rhythms – called ventricular tachycardia and ventricu­lar fibrillation – an internal “shocking” device may be the best protection against sudden cardiac arrest (SCA).

What is an ICD?

An implantable cardioverter defibrillator (ICD) is a device that can detect dangerously fast heartbeats and give a lifesaving shock to correct the heart's rhythm. A person with an ICD has the equivalent of a paramedic sitting on his shoulder, always watching and ready to give the heart "the paddles," as seen on many hospital and emergency television shows.

Before Your Visit

Talking to your Doctor

By talking openly to your doctor, you will know what treatments are best for you. Your doctor can provide advice based upon your concerns, value and priorities; a process called shared decision-making. Even if you simply want to follow your doctor’s recommendations, it is important to have a conversation about what matters most to you.


How does an ICD work?

An ICDs is a device that is about the size of a deck of cards and is most often implanted below the collarbone in a pocket under the skin. A different type of defibrillator may be placed along a patient's left side. Like pacemakers, an ICD contains computer cirduitry, a battery, and wires called "leads" that usually go through a vein into the heart. The leads stay in contact with the heart muscle on one end, while the other end is connected to the generator. These are called transvenous ICDs. Transvenous ICDs also act as pacemakers and can treat slow heart rhythms by pacing as well. A different type of ICD called a subcutaneous ICD may be placed along the patient’s left side. The lead is tunneled under the front of the chest and does not go directly to the heart. It is very effective at treating life-threatening heart rhythms but does not provide routine pacemaker function. The battery in the ICD generator lasts 5-8 years and must be replaced when it runs out.

The ICD is programmed to record signals from the heart. All of the heart rhythm information is stored in the ICD memory. This information is available to your doctor at routine clinic visits and through remote data transmissions from home. ICD follow up is very important for each patient, to make sure the ICD battery is good and that the device is working properly.

Pacing signals from the ICD are not felt by the patient, but the shock signal delivered by an ICD has been described as a "kick in the chest." Medication or other treatments may be given to try to prevent recurring shocks.

When is an ICD used?

People with heart muscle damage or heart failure have a greater chance of having dangerously fast heart rhythms. ICDs are often recommended for people who have this problem even if they have not yet had an abnormal heart rhythm. ICDs are also recommended for patients who have already experienced and recovered from dangerously fast heart rhythms, as they can often recur in such individuals. Other heart conditions such as cardiac sarcoid, hypertrophic cardiomyopathy, or inherited arrhythmia syndromes like long QT syndrome may predispose patients to life-threatening heart rhythms. If your doctor feels you are at increased risk, they may recommend an ICD.

ICDs do not prevent heart attacks, which are caused by blockages in the heart’s arteries, but do treat abnormal rhythms sometimes associated with heart attacks. ICDs do not keep people alive forever. People with ICDs can die of causes other than heart rhythm problems.

Keep Exploring

Heart Rhythm Disorders
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This section is for pediatric patients and families living with heart rhythm disorders and heart rhythm disorders related to congenital heart disease (CHD).
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Common Treatments
Learning about the underlying cause of any heart rhythm disorder provides the basis for selecting the best treatment plan. Information and knowledge about care options, and their risks and benefits help you work with your health care provider to make the best choices.
Since other heart disorders increase the risk of developing abnormal heart rhythms, lifestyle changes often are recommended. Living a “heart healthy” lifestyle can ease the symptoms experienced with heart rhythm disorders and other heart disorders, and can be beneficial to overall patient health.
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The heart is a fist-sized muscle that pumps blood through the body 24 hours a day, 365 days a year, without rest. The normal heart is made up of four parts: two atria on the top of the heart (right atrium and left atrium), and two ventricles (right ventricle and left ventricle) which are the muscular chambers on the bottom of the heart that provide the major power to pump blood.