An ICD is designed to respond to arrhythmias, either by ‘pacing’ the heart back into a normal rhythm or by giving a shock to the heart.

This sounds scary, and many people with ICDs are anxious about the possibility of this happening. Although a shock is potentially life-saving, it can be distressing, and a sign that someone would otherwise have had a cardiac arrest. This in itself can be distressing.

If someone has a fast or irregular heart beat they may be aware of it, and may feel faint or dizzy. The ICD monitors the heart to see if it corrects itself. The person may be aware of a possible shock happening. People who have been awake when they received a shock have said it is like being thumped or kicked in the chest. This is a temporary feeling. 

However, for most people their arrhythmia will cause loss of consciousness and so they will be unaware of the shock happening. 

Most people recover quite quickly from a shock, and do not have any lasting physical symptoms, although it is often a good idea to rest before going back to normal activities. However, some people have an emotional reaction to having a shock, as it can be upsetting. 

Your doctors will talk to you about what to do if you receive a shock. They may ask you to visit the ICD clinic for a check-up following a shock. You would usually only need an ambulance or to go to hospital
if you continue to feel unwell, or you receive more than one shock.

What are inappropriate shocks?

An inappropriate shock is when an ICD gives a shock to the heart when it is not necessary. This can sometimes happen if the ICD detects a fast heart rhythm that is not dangerous. The ICD is programmed to reduce the possibility of this happening. If it does happen, your ICD will need to be checked to see why it has happened, and may need to be reprogrammed so that it doesn’t happen again.

What happens if someone touches me when I have a shock?

If someone is touching you when your ICD goes off, they will feel a small shock themselves. This is a bit like a static shock and is harmless.

©Cardiomyopathy UK. April 2018