An implantable cardioverter defibrillator (ICD) is a small electrical device that monitors the rhythm of your heartbeat. When it detects an abnormal rhythm (arrhythmia) it works to restore the normal heartbeat.

An implantable cardioverter defibrillator (ICD) is a small matchbox-shaped device that is inserted under your skin. It is powered by a battery and has thin electrical leads that connect it to your heart. The battery lasts 4-7 years before a new device needs to be inserted.

An ICD monitors the rhythm of your heart beat. A normal heart beat is roughly 60-100 beats per minute. This is controlled by your heart’s electrical system. Abnormal heart rhythms (arrhythmias) occur if there are problems with this electrical system.

When there is an arrhythmia, the ICD sends tiny electrical pulses to restore a normal heart beat. These pulses, known as pacing, can’t be felt by most people. If there is a more serious problem with your heart rhythm, the ICD may deliver an electrical shock to fix it. This is known as defibrillation.

ICDs treat life threatening heart rhythm problems, but they do not prevent a heart attack.

There are two types of ICD.

Having an ICD implanted and getting used to living with the device can be stressful and overwhelming. We are here to help with professional counselling and emotional support programmes, our Nurse Support Line, information events and our online community.

For more information on these supports for you and your family, visit our heart support page

Why ICDs are used

ICDs are used to treat serious heart rhythm issues.

Most people have an ICD because their heart has been damaged by a heart attack or they have an inherited heart problem such as long QT syndrome, cardiomyopathy or Brugada syndrome that puts them at risk of an arrhythmia. An ICD might also be used if someone has had a cardiac arrest or lives with heart failure.

Before your doctor decides if you need an ICD, you’ll have several tests to find out more about your heart function and your risk of life-threatening arrhythmias. These could include an ECG, echo, Holter monitor, exercise stress test, angiogram or an electrophysiology study.

How an ICD is inserted

ICDs are inserted under the skin in the left side of the chest.

A traditional ICD is inserted just below your left shoulder with the leads threaded through a large vein into the heart. A subcutaneous ICD is inserted in the left side of the chest with leads running along your ribs and breast bone but not directly into the heart.

The ICD is inserted under local anaesthetic. You will remain awake during the surgery but should not feel anything. The procedure can take a few hours, depending on the number of leads inserted with the ICD.

When the ICD is in place, your doctor will programme it to treat your specific heart rhythm problem. They will also test the ICD, which may involve speeding up your heart into a disorganised rhythm to make sure the ICD can deliver a shock to fix it.

You are usually asked to have nothing to eat or drink for about 6 hours before your ICD surgery. Ask your cardiac team if you can take your usual medications and follow their instructions. For instance, if you are taking any blood thinners, you may need to stop them 3-5 days before surgery.

After your surgery, you will have a chest x-ray to check the position of the ICD and leads and make sure there is no problem with the lungs. The opening where the ICD was placed will be covered with a dressing for a few days. You will receive detailed information on how to care for the ICD site and let the ICD settle in to your body before you go home.


Most people have no problems having an ICD inserted. Like any surgery, there is a small risk of bleeding, swelling or infection at the site. Your healthcare team will tell you what to look for and how to manage it. Bruising is common and may spread around your chest and to your arm.

Other possible risks include:

However, serious complications when having the device fitted are rare.

Adjusting to an ICD

Everyone’s experience of ICD treatment will be different. Here, we outline what you can generally expect in the weeks and months after the ICD is fitted.

What to expect after surgery

Your wound and your shoulder will be a little sore for a few days after the ICD is inserted. It is important to let the wound heal properly and follow your healthcare team’s instructions on how to care for it. Your doctor will give you advice on pain medicine if you need it. If the wound gets more painful or becomes red or swollen, contact your hospital immediately so that they can check for infection.

For the first 6 weeks after surgery, avoid heavy lifting and raising your arm above shoulder level on the side of the device. Otherwise, use your arm as normal, as this will stop it getting stiff.

How to adjust to ICD treatment

What to do if you hear an ICD alarm

Your ICD has a built-in alarm. Once fitted, it will perform regular self-checks and beep if something is not right. The most common causes for the alarm are:

Other causes include problems with the ICD leads and being too close to a strong magnet (see electrical and electronic devices below). The alarm should stop once you move away from the magnet.

If you hear a beeping tone, contact your cardiology team as soon as possible so they can arrange to check the ICD for the cause of the alarm. These checks will be made by a cardiac physiologist, at your usual hospital. If you are travelling, any hospital with a cardiology service can examine your ICD.

There is no need to seek immediate medical help if you hear an alarm unless you feel unwell or receive a shock from your ICD.

When should I get medical help?

Call your healthcare team if:

They will arrange to check your ICD.

Call 999 or 112 for an ambulance if:

Living with an ICD


Many people with ICDs also take medicine to help control irregular heart rhythms. These medicines are designed to make arrhythmias less severe and easier to correct. They may also reduce how often you experience serious heart rhythm issues. Take all the medicines you’ve been prescribed and don’t make any changes without first talking with your healthcare team.

Returning to work

When you can return to work will depend on your heart condition and any other conditions you have. Your cardiology team can give you more information to help you decide how and when to go back to work. Depending on your heart condition, you may need to change how you work or the type of work you do if your job is very physically demanding or stressful.


Under Road Safety Authority guidelines, you cannot drive a bus, truck or articulated vehicle when you have an ICD. You may drive a car 6 months after your surgery once your cardiologist approves. If you receive a shock from your device, you must wait another 6 months before driving again.

Other waiting periods apply if:

You can learn more from the RSA website.

Sports and physical activity

Walking and other exercise is good for you, and you may receive other lifestyle advice to help you manage your heart health. But what is considered a safe level of physical activity with an ICD will depend on your individual heart condition.

Your healthcare team can give you more information on what level of physical activity is safe for you.

Sex and intimacy

It is safe to have sex when your wound has healed and when you feel ready to. The normal increase in heart rate during sex shouldn’t cause your ICD to shock you. If your ICD does deliver a shock during sex, it won’t hurt the person you are with. Choose a position that avoids pressing on your ICD and make sure your partner knows a shock won’t hurt them.

Electrical and electronic devices

Strong electro-magnetic fields can interfere with your ICD, but most common electrical devices that are in good working order are safe to use.


People with ICDs usually don’t have problems with air travel.

Medical tests

If you are having any medical or dental treatment, tell the medical staff that you have an ICD in advance.

If you need to have a test such as an X-ray or magnetic resonance imaging (MRI) scan, tell the technician about your ICD ahead of time. Give as much notice as possible so the centre can find out if an MRI is safe for your particular ICD. The test centre will also arrange for a cardiac physiologist to switch off your ICD right before the scan and switch it back on afterwards.

Living with an ICD – tips to remember

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