What is an Implantable Cardioverter Defibrillator – ICD ?

By June Shannon Heart News   |   2nd Jul 2021

Danish Footballer Christian Eriksen has been fitted with an ICD following a cardiac arrest during the European Championships, but what is an ICD and how does it work?

What is an ICD?

An ICD or Implantable Cardioverter Defibrillator is a battery powered device that is placed inside your chest cavity under your skin near your shoulder. Electrode leads connect the ICD to the inside of your heart. The battery lasts 4-7 years after which a new unit will be inserted.

The ICD, which is roughly the same size as a matchbox, continuously monitors your heart rhythm. It can either act as a pacemaker detecting when the heart beat is too slow and sends tiny electrical signals to your heart, or if your heart beat it too fast or chaotic, it emits shocks to bring the heart back into normal rhythm.

Why are ICDs implanted?

ICDs are generally implanted in people who have had a heart rhythm problem (arrhythmia) or possibly even a cardiac arrest. However, sometimes people who have not had any symptoms, but are considered at risk of developing a serious heart arrhythmia may have the device inserted as a precaution.

Most people have an ICD because their heart has been damaged by a heart attack or because they have a heart condition, often inherited, that puts them at risk of developing arrhythmias.

ICDs can be implanted if someone has had a heart attack that has damaged their heart’s electrical system. You could also have an ICD because you have had a ventricular arrhythmia before. A common reason for arrhythmias is inherited heart problems such as long QT syndrome, cardiomyopathy, or Brugada syndrome.

Some people with heart failure have specialised ICDs that help both heart ventricles work together and improve the heart’s ability to pump blood.

What causes an abnormal heart rhythm?

Your heart’s electrical system controls a normal rhythmic heartbeat of 60-100 beats per minute. Abnormal heart rhythms (arrhythmias) are caused by problems with this electrical system. The heartbeat may be too slow or too fast, steady or chaotic. Some arrhythmias are dangerous and can cause sudden cardiac death, while others are bothersome but are not life-threatening. The most serious and life-threatening arrhythmias come from your heart’s lower chambers, the ventricles.

An ICD or Implantable Cardioverter Defibrillator is a battery powered device that is placed inside your chest cavity under your skin near your shoulder.


What does it feel like when the ICD delivers a shock?

You might feel the abnormal heart rhythm before the ICD treats the rhythm disturbance. If you think that your ICD might deliver a shock, sit or lie down. If you are with someone, tell them how you feel.

When the ICD is pacing your heart, treating a fast rhythm, you can have a painless fluttering feeling. If this treatment is unsuccessful, the ICD will deliver an electric shock. This electric shock will usually feel like a hard thump to your chest and can be quite uncomfortable. You may feel dizzy or blackout (faint) shortly before the shock is delivered.

Once the ICD has delivered its treatment and your normal heart rhythm has been restored, it is a good idea to rest for a short while. You don’t need to go to hospital right away. Telephone your hospital to tell them you’ve had a shock and they will arrange to check your ICD.

If you fainted before your ICD shocked you, if you still feel unwell after the ICD has delivered a shock or the ICD gives you more than one shock, you should call for an ambulance by dialling 999 or 112.

Everyone’s experience of ICD treatment will be different. The strength and number of treatments from an ICD will differ from person to person. Some people have many shocks in a year while others may never have one.

It is very important to know why you have an ICD and to understand your condition. If you have a good knowledge of your particular heart condition and manage your symptoms by taking your medicines as prescribed and following your doctor’s lifestyle advice, this will reduce your risk of having a shock.

Living with an ICD

It is important to remember that you can live a full and active life with an ICD

Will I have to take medicines to treat my heart condition?

Many people with ICDs also take medicine to help control irregular heart rhythms. Antirhythmic medicines are designed to make arrhythmias that affect you less severe and easier to correct. These medicines may also reduce how often you experience these serious heart rhythm disturbances.

What about getting back to work?

When you can go back to work will depend on the seriousness of your heart problem, your age and if you have any other illnesses. If you have an ICD solely as a precaution, you can probably return to work almost immediately. If you have had serious heart problems, recovery may take at least 6 weeks.

Depending on the seriousness of your heart illness, if your job is very physically demanding or stressful, you may need to change how you work or change the type of work you do.

It is very important to know why you have an ICD and to understand your condition.


Is it ok to drive with an ICD?

Currently, there is no Irish legislation regarding non-commercial driving with an ICD implanted. If you have a history of collapse, there will be driving restrictions. It is important to discuss driving with your cardiologist, your employer, and your insurance company. You should not drive until your doctor clears you to do so.

If your job involves driving, check with the driving licence authority and your employer to see if there are any restrictions that may apply to you.

Is it safe to have sex?

It is safe to have sex when you feel ready to.

If your ICD delivers a shock while you are having sex, it won’t hurt the person you are with. However, the normal increase in heart rate during sex shouldn’t cause your ICD to shock you.

Can I still play sports with an ICD implanted?

Walking and other exercise is good for you. In general, you should avoid contact sports and activities that could damage your ICD or be dangerous if the ICD delivers a shock (such as climbing a ladder). Make sure you are not alone when you go swimming. Talk to your doctor if you are considering strenuous upper body activities such as weight lifting. The level of physical activity that is safe for you will depend on your particular heart condition. Your doctor or cardiologist can give you more information on what is a safe level of physical activity for you.

Can I travel abroad? 

People with ICDs should have no problems with air travel. However, airport metal detectors (both the walk-through and handheld wand metal detectors) can cause some electrical interference. You should tell airport security staff that you have an ICD and show your official (long version) ICD card before you get to the metal detector.

What about Electromagnetic Interference (EMI)

Most common electrical devices that are in good working order are safe to use if you have an ICD. Strong electromagnetic fields can interfere with your ICD. In general, all household equipment can be used, including microwaves and computers. Use your mobile phone on the opposite side to your ICD and don’t carry it in your breast pocket.

At entrances to shops and other facilities with electronic security systems, walk normally through the theft detection systems. Don’t stop close to the equipment, otherwise, it is quite safe. Avoid wearing magnetic bracelets or magnets near your chest.

Your ICD is there to help you improve your quality of life


Will I have any difficulties with medical procedures?

Magnetic Resonance Imaging (MRI) testing may not be allowed if you have an ICD though some of the newer devices may be MRI compatible but will need to performed in a centre experienced in dealing with this issue. Some other types of medical equipment can also interfere with your ICD. If you are due to have any dental or medical tests or procedures, please tell your dentist or doctor that you have an ICD at the time of making the appointment.

What about ICD Alarms?

Many types of ICDs have in-built alarms to let you know if the battery is running low or if there is a problem with the device. If you hear your ICD beep or make a noise, contact your hospital clinic to let them know.


The Irish Heart Foundation ICD Support Group

The Irish Heart Foundation ICD Support Group is run by people who have an ICD and is supported by the Irish Heart Foundation. ICD Support Group is for adults and children with ICDs and their families. For more information on this support group please see here. (link to ICD Support Group)

The Irish Heart Foundation helpline: Our nurses are available on phone and email support  Monday to Friday 9 am to 1 pm. Call 01 6685001 or email support@irishheart.ie


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