ICDs (Implantable Cardioverter Defibrillators)

ICDs are programmed to pick up and stop life-threatening arrhythmias

ICDs are programmed to pick up and stop life-threatening arrhythmias

ICDs are life-saving devices, similar to pacemakers. They are programmed to pick up and stop specific life-threatening arrhythmias (abnormal heart rhythms) and restore your heart to its normal rhythm.

An ICD consists of a small 'box' with pacing wires which are situated within the chambers of your heart and provide information about your heart's rhythm. An ICD is fitted in the same way as a pacemaker.

Why do I need an ICD?

ICDs can be used:

  • If you are at risk of specific life–threatening arrhythmias (known as 'primary prevention')
  • If you have survived a specific life–threatening arrhythmia (known as 'secondary prevention')

There are two types of arrhythmia that are treated with ICDs:

  • Ventricular tachycardia (VT): this is when the ventricles (bottom chambers of your heart) produce abnormal electrical signals which cause your heart to beat very quickly. This can interfere with the pumping action of your heart and may cause your heart to stop beating.
  • Ventricular fibrillation (VF): this happens when irregular electrical signals are rapidly produced throughout the ventricles. In VF your heart is unable to contract and pump blood. It will stop beating unless an electrical shock is given to restore your heart rhythm.

If you have heart failure you may need a special type of device called a CRT-D (cardiac resynchronisation therapy defibrillator) device. As well as treating heart arrhythmias, a CRT-D device also synchronises your heart's chambers to contract and relax in a regular way, thus improving the pumping action of your heart.

How does an ICD work?

An ICD can work like a basic pacemaker to stabilise your heart's rhythm and / or cardiovert (correct abnormal heart ryhthm) your heart through the delivery (or 'firing') of a controlled electrical 'shock'. This process, called defibrillation, stops a dangerous arrhythmia and allows the normal rhythm of your heart to start again. Sometimes this is simply referred to as your ICD 'firing'.

Each device is programmed, specifically, to respond to your individual needs. The programme can be modified if necessary. Depending on your heart rate, an ICD can:

  • Deliver pacing pulses to increase your heart rate if it is too slow. You are usually unaware of this.
  • Deliver fast pulses to help to restore a normal rhythm when your heart rate is too fast. You may be unaware of this or you may notice palpitations and / or dizziness.
  • Perform cardioversion: an electric shock is delivered to your heart to stop a dangerous heart rhythm (such as ventricular tachycardia or ventricular fibrillation). This can be quite painful. However, if your heart rhythm is so fast that it causes loss of consciousness then you may be unaware of this happening.
  • Record the electrical activity so that your heart's rhythm and any treatments delivered can be examined.

Tests and investigations

You will need some tests and investigations to help your cardiologist (heart doctor) to decide if an ICD will help you. These may include:

More advanced tests, such as an Adenosine Test and Electrophysiology (EP) studies, may sometimes be needed.

Deciding to have an ICD fitted

If your cardiologist feels that an ICD would be helpful to you then he / she will explain to you about your arrhythmia and why you need to have an ICD. You may want to talk about:

  • The benefits of having an ICD fitted.
  • How having an ICD fitted will affect your everyday life.
  • What would happen to you if you choose not to have one fitted.

Switching an ICD off

At the end of life an ICD could keep your heart beating artificially. This can be the case for both heart and non-heart related conditions or when your quality of life has become very poor. For some people there comes a point when the decision needs to be made as to whether an ICD is still appropriate. The decision to turn off an ICD can be very difficult and should involve discussions with close family and your doctor / specialist nurse.

Turning off an ICD is a simple, non-invasive procedure, which can be performed by a cardiac physiologist (technician). It is important to know that specialised care will be provided to support you if the decision to switch off your ICD is made. Specialised care, referred to as palliative care, ensures that all your needs will be met and that you and your family are well supported.

  • Information about living with an ICD is available here.
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