Date Updated: 12/02/2021


An implantable cardioverter-defibrillator (ICD) is a small battery-powered device placed in the chest to detect and stop irregular heartbeats (arrhythmias). An ICD continuously monitors the heartbeat and delivers electric shocks, when needed, to restore a regular heart rhythm.

You might need an ICD if you have a dangerously fast heartbeat that keeps your heart from supplying enough blood to the rest of your body (such as ventricular tachycardia or ventricular fibrillation) or if you are at high risk of such a heart rhythm problem (arrhythmia), usually because of a weak heart muscle.

An ICD differs from a pacemaker — an implantable device that can prevent dangerously slow heartbeats.


An ICD is a type of cardiac therapy device. There are two basic types:

  • A traditional ICD is implanted in the chest, and the wires (leads) attach to the heart. The implant procedure requires invasive surgery.
  • A subcutaneous ICD (S-ICD) is another option that's implanted under the skin at the side of the chest below the armpit. It's attached to an electrode that runs along the breastbone. An S-ICD is larger than a traditional ICD but doesn't attach to the heart.

Why it's done

An ICD constantly monitors for irregular heartbeats and instantly tries to correct them. It helps when the heart stops beating effectively (cardiac arrest).

Your health care provider may recommend an ICD if you've had signs or symptoms of a certain type of irregular heart rhythm called sustained ventricular tachycardia, including fainting. An ICD might also be recommended if you survived a cardiac arrest. Other reasons you may benefit from an ICD are:

  • A history of coronary artery disease and heart attack that has weakened the heart
  • An enlarged heart muscle
  • A genetic heart condition that increases the risk of dangerously fast heart rhythms, such as some types of long QT syndrome
  • Other rare conditions that may affect the heartbeat

A health care provider may recommend an S-ICD if there are structural defects in the heart that prevent attaching wires to the heart through the blood vessels.


Possible risks of having an ICD implanted include:

  • Infection at the implant site
  • Swelling, bleeding or bruising
  • Blood vessel damage from ICD leads
  • Bleeding around the heart, which can be life-threatening
  • Blood leaking through the heart valve (regurgitation) where the ICD lead is placed
  • Collapsed lung (pneumothorax)
  • Movement (shifting) of the device or leads, which could lead to cardiac perforation (rare)

How you prepare

Before you get an ICD, your health care provider will order several tests, which may include:

  • Electrocardiography (ECG or EKG). An ECG is a quick and painless test that measures the electrical signals that make the heart beat. Sticky patches (electrodes) are placed on the chest and sometimes the arms and legs. Wires connect the electrodes to a computer, which displays the test results. An ECG can show if the heart is beating too fast, too slow or not at all.
  • Echocardiography. This noninvasive test uses sound waves to create pictures of the heart in motion. It shows the size and structure of the heart and how blood is flowing through the heart.
  • Holter monitoring. A Holter monitor is a small, wearable device that keeps track of the heart rhythm. It may be able to spot irregular heart rhythms that an ECG missed. You typically wear a Holter monitor for 1 to 2 days. Wires from sensors on the chest connect to a battery-operated recording device carried in a pocket or worn on a belt or shoulder strap.

    While wearing the monitor, you may be asked to keep a diary of your activities and symptoms. Your health care provider will usually compare the diary with the electrical recordings and try to figure out the cause of your symptoms.

  • Event recorder. If you didn't have any irregular heart rhythms while you wore a Holter monitor, your health care provider may recommend an event recorder, which can be worn for a longer time. There are several different types of event recorders. Event recorders are similar to Holter monitors and generally require you to push a button when you feel symptoms.
  • Electrophysiology study (EP study). The health care provider guides a flexible tube (catheter) through a blood vessel into the heart. More than one catheter is often used. Sensors on the tip of each catheter send signals and record the heart's electricity. A health care provider uses this information to identify the area that is causing the irregular heartbeat.

What you can expect

Before the procedure

If you're having an ICD implanted, you'll likely be asked to avoid food and drinks for at least 8 hours before the procedure.

Talk to your health care provider about any medications you take and whether you should continue to take them before the procedure to implant an ICD.

During the procedure

A health care provider will insert an IV into your forearm or hand and may give you a medication called a sedative to help you relax.

You will likely be given general anesthesia (fully asleep).

During surgery to implant the ICD, the doctor guides one or more flexible, insulated wires (leads) into veins near the collarbone to the heart using X-ray images as a guide. The ends of the leads attach to the heart. The other ends attach to a device (shock generator) that's implanted under the skin beneath the collarbone. The procedure to implant an ICD usually takes a few hours.

Once the ICD is in place, your doctor will test it and program it for your specific heart rhythm needs. Testing the ICD might require speeding up the heart and then shocking it back into a regular rhythm.

Depending on the problem with the heartbeat, an ICD could be programmed for:

  • Low-energy pacing. You may feel nothing or a painless fluttering in your chest when your ICD responds to mild changes in your heartbeat.
  • A higher energy shock. For more-serious heart rhythm problems, the ICD may deliver a higher energy shock. This shock can be painful, possibly making you feel as if you've been kicked in the chest. The pain usually lasts only a second, and there shouldn't be discomfort after the shock ends.

Usually, only one shock is needed to restore a regular heartbeat. Some people might have two or more shocks during a 24-hour period.

Having three or more shocks in a short amount of time is called an electrical or arrhythmia storm. If you have an electrical storm, you should call 911 or seek emergency medical help to see if your ICD is working properly or if you're having irregular heartbeats.

If necessary, the ICD can be adjusted to reduce the number and frequency of shocks. Medications may be needed to make the heart beat regularly and decrease the risk of an ICD electrical storm.

After the procedure

You'll usually be released on the day after the ICD procedure. You'll need to arrange to have someone to drive you home and help you while you are recovering.

The area where the ICD is implanted can be swollen and tender for a few days or weeks. Your health care provider might prescribe pain medication. Aspirin and ibuprofen aren't recommended because they may increase the risk of bleeding.

You'll usually need to avoid abrupt movements that raise your left arm above your shoulder for up to eight weeks so the leads don't move until the area has healed. You may need to limit your driving, depending the type of ICD received. Your health care provider will give you instructions on when it's safe to return to driving and other daily activities.

For about four weeks after surgery, your health care provider might ask you to avoid:

  • Vigorous, above-the-shoulder activities or exercises, including golf, tennis, swimming, bicycling, bowling or vacuuming
  • Heavy lifting
  • Strenuous exercise programs

Your health care provider will probably tell you to avoid contact sports indefinitely. Heavy contact may damage the device or dislodge the wires.

Long-term precautions

Problems with an ICD due to electrical signals (electrical interference) are rare. Still, take precautions with the following:

  • Cellular phones and other mobile devices. It's safe to talk on a cellphone, but avoid placing a cellphone within 6 inches (about 15 centimeters) of an ICD site when the phone is turned on. Although unlikely, an ICD could mistake a cellphone's signal for a heartbeat and slow the heartbeat, causing symptoms such as sudden fatigue.
  • Security systems. After surgery, you'll receive a card that says you have an ICD. Show your card to airport personnel because the ICD may set off airport security alarms.

    Also, hand-held metal detectors often contain a magnet that can interfere with an ICD. Limit scanning with a hand-held detector to less than 30 seconds over the site of your ICD or make a request for a manual search.

  • Medical equipment. Tell health care providers that you have an ICD. Some procedures, such as magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and radiofrequency or microwave ablation may not be recommended if you have an ICD. Your health care provider can tell you if you need an alternative test.
  • Power generators. Stand at least 2 feet (0.6 meters) from welding equipment, high-voltage transformers or motor-generator systems. If you work around such equipment, your health care provider can arrange a test in your workplace to see if the equipment affects your ICD.
  • Headphones and wireless chargers. Headphones may contain a magnetic substance that can interfere with an ICD. Keep headphones and wireless chargers at least 6 inches (about 15 centimeters) from an ICD.
  • Magnets. Magnets may affect an ICD, so it's a good idea to keep magnets at least 6 inches (15 centimeters) from the ICD site.

Devices that pose little or no risk to an ICD include microwave ovens, televisions and remote controls, AM/FM radios, toasters, electric blankets, electric shavers and electric drills, computers, scanners, printers, and GPS devices.

Driving restrictions

If you have an ICD to treat ventricular arrhythmia, driving a vehicle may pose risks to yourself and others. The combination of arrhythmia and shocks from an ICD can cause fainting, which would be dangerous while driving.

Many countries have driving restrictions for people with ICDs. If your ICD was implanted due to a previous cardiac arrest or ventricular arrhythmia, your health care provider may recommend waiting several months before driving or operating a vehicle. If you have a shock, with or without fainting, tell your health care provider. Usually, you'll be discouraged from driving until you've been shock-free for several months.

If you have an ICD but have no history of life-threatening arrhythmias, you can usually resume driving about a week after your procedure if you've had no shocks. Discuss your situation with your health care provider.

You usually can't get a commercial driver's license if you have an ICD.


An ICD is the main treatment for anyone who has survived cardiac arrest. ICDs are increasingly used in people at high risk of sudden cardiac arrest. An ICD lowers the risk of sudden death from cardiac arrest more than medication alone.

Although the electrical shocks can be unsettling, they're a sign that the ICD is effectively treating a heart rhythm problem and protecting against sudden death.

The lithium battery in an ICD can last 5 to 7 years. The battery is typically checked during regular checkups, which should occur about every six months. When the battery is nearly out of power, the generator is replaced with a new one during a minor outpatient procedure.

ICDs and end-of-life issues

If you have an ICD and become terminally ill, your ICD will still deliver shocks if it isn't deactivated. A health care provider can perform a simple procedure to turn off the ICD, if desired. Turning off the device can prevent unwanted shocks and unnecessary suffering. Doing so won't immediately cause the heart to stop.

Talk to your health care provider about your wishes. Also talk to family members or the person designated to make medical decisions for you about what you'd like to do in an end-of-life care situation.

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