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Implantable cardioverter defibrillators (ICDs)

An ICD is a device that detects fast heart rhythms and treats them with small electrical impulses or a shock. They consist of a small metal box which is connected to the heart via a wire, or 'lead'.

The rhythm abnormalitites (arrhythmias) that are treated by an ICD include:

  • Ventricular tachycardia (rapid regular beating of the main pumping chambers of the heart, ventricles)

  • Ventricular fibrillation (rapid irregular beating of the ventricles)

Both of these arrhythmias interfere with the pumping action of the heart and can lead to loss of conciousness and sudden cardiac death.  They tend to occur in patietns with with coronary artery disease or diseases of the heart muscle (cardiomyopathies).

Who needs an ICD ?

An ICD should be considered in patients who have already had a life-threatening cardiac rhythm abnormality (secondary prevention) or in those who are at risk of developing it (primary prevention).

Secondary prevention

For patients who fall under the following categories:

Primary prevention
If patients have not had ventricular tachycardia or fibrillation but are at risk of developing it, it is essential to know the NYHA class, the left ventricular ejection fraction (LVEF) and the QRS duration on the heart trace (ECG). The choice of device is shown on the following table:
















​In addition, ICDs should be considered in:


  • Familial cardiac conditions with a high risk of sudden cardiac death including long QT syndrome, hypertrophic cardiomyopathy, Brugada's syndrome or arrhythmogenic right ventricular cardiomyopathy (ARVC), or have undergone surgical repair of congenital heart disease.​

​The implantation procedure

Transvenous ICD: The implantation procedure is similar to implatation of a pacemaker. It will will be performed in the “Cardiac Catheter Lab”. The doctor will anaesthetise the area with local anaesthetic.  You will feel a needle prick and a mild stinging sensation from the local anaesthetic but there is little or no pain during the procedure. Intravenous sedation can also be given to make you feel sleepy. A small incision will be made on the upper part of your chest, just below the collar bone. A small pocket will be made through the incision to accommodate the ICD box. The lead or leads will then be threaded through one of the veins and the tips anchored in your heart.  You will not feel the pacemaker leads inside the body, but you may feel extra heart beats as we introduce the leads into your heart.

Subcutaneous ICD: This device avoids putting devices or leads in the circulation. The 'box' is places on the left side of the chest and a small lead is implanted under the skin of the chest. The advantage of this device is that it avoids the dangers of leaving leads inside the circulation. In some cases, it is necessary to test the ICD by inducing a rapid heart rhythm and allowing it detect and treat the arrhythmia. You will be heavily sedated for this.

Preparation for pacemaker implantation
• Let us know whether you are taking anticoagulants (eg. warfarin) or metformin, as you may need to stop these prior to the procedure.

• Take a bath or shower the night before and wash your chest, shoulders and armpits.

• Do not eat for 6 hours before the test. You may drink water until one hour before.

• Please bring all your tablets in their original packets. All valuables should be left at home.

• You should be able to go home the day following the procedure. It is necessary to monitor the ICD at various times and your length of stay can only be decided at the time of the procedure. In case you need to stay overnight, bring your dressing gown, slippers and overnight toiletries. Please make sure that someone can collect you.

​On arrival at the hospital
A nurse will take your blood pressure, temperature, pulse, height and weight. A doctor will take your medical history, examine you and take a blood sample. The procedure will be explained to you by a doctor and a nurse. This is an opportunity for you to ask questions and tell us any concerns you may have about the procedure.The doctor will then ask you to sign a consent form showing that you understand what is involved and agree to the procedure.

​After the ICD implantation
• Keep your wound clean and dry.  Expect your shoulder to ache a little. You may take a painkiller if required, but be careful not to exceed the recommended dosage. Avoid lifting and manual work raising your arm for 1 week.

• If after 48 hours you notice new redness, soreness or oozing at the implantation site, please contact us directly, either through the secretary or the hospital ward.

• You will be given a brief letter for your GP. The stitches can be removed at 7-10 days. We will give you further instructions regarding this.

Lifestyle after an ICD
  • Keep your ICD card with you

  • Have normal sexual activity

  • The device will not cause harm to another person, even if you are touching.

  • Domestic electrical equipment can be safely used. Interference  from radios, fridges, cookers, computers and microwaves will not affect the ICD.

  • Security alarms: the ICD amy set them off, so you need to inform the guards that you have an ICD. 

  • Exposure to strong magnetic field, such as in arc welding, should be avoided. Our technicians will be able to assess specialised electrical equipment at your place of work. 

  • Mobile phones should be kept about 15 cm away from the ICD. It is best to hold the phone over the other ear.


In the UK, patients must notify the DVLA after ICD implantation. The guidelines are complex, but this is summary:

  • No driving for 6 months off after a shock is delivered, with some exceptions

  • No driving for 1 month after revision of the leads

  • No driving for 1 month after altering drug treatment for the arrhythmia

  • No driving for 1 week after an ICD box change

Group 2 drivers (LGV/PCV) are permanently barred after ICD implantation

Implantation of a conventional ICD

Implantation of a subcutaneous ICD

Having an ICD

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