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Heart disease health centre

Having a defibrillator fitted

BMJ Group Medical Reference


This information tells you about an operation to put a device in your chest that helps your heart beat normally. It explains how the operation is done, how the device can help you, what the risks are, and what to expect afterwards.

The benefits and risks described here are based on research studies and may be different in your hospital. You may want to talk about this with the doctors and nurses treating you.

What is a defibrillator?

An implantable defibrillator is a device that's put in your chest to stop an abnormal heart rhythm, particularly one where the lower part of your heart beats too quickly. You may hear these devices called implantable cardiac defibrillators or implantable cardioverter defibrillators. Either way, they're often called ICDs for short.

Your heart usually beats at 60 to 100 beats per minute. An abnormal heart rhythm can mean your heart beats at 120 to 200 beats per minute, or even faster. Your heart muscle may flutter instead of beating strongly. If this happens, your heart can stop pumping blood around your body. If your heart isn't made to beat normally again, you will die.

An electric shock can get your heart beating normally again. You may have seen this in medical dramas on television, with actors using electric paddles to shock someone's heart into beating.

An ICD works in the same way as the paddles. It shocks your heart into beating steadily if your heart suddenly beats too fast. The idea is that a small shock given early will slow your heartbeat and save your life.

An ICD is about the size of a pack of cards. It's put under the skin just below your collarbone on the left side of your chest. The device is powered by a battery and has an electric circuit that checks your heartbeat. A lead connects the device to your heart.

If your heart starts to beat very quickly, the ICD sends an electric signal to shock it back into a normal rhythm.

A fast heartbeat is linked to several heart conditions. The information here is only about people who have a heart condition called heart failure.

Heart failure is when your heart stops pumping properly because it's been damaged. About a third of people with heart failure get a dangerously fast heartbeat. [1] A fast heartbeat increases the risk that someone with heart failure will die suddenly.

Is a defibrillator suitable for me?

Not everyone with heart failure will need an ICD. Your doctor may suggest one if he or she thinks you have a high risk of dying from your abnormal heart rhythm.

Guidelines from the National Institute for Health and Clinical Excellence (NICE), the government body that advises doctors about treatments, say that you should be offered an ICD if: [2]

  • Your heart stopped pumping because of a fast rhythm and was restarted

  • Your heart beats too fast for long periods (more than 30 seconds), and it does so suddenly and unexpectedly. You also have blackouts or other signs that your blood flow is being restricted.

  • Your heart beats too fast for long periods, but without blackouts or more serious symptoms. Your heart also struggles to pump out enough blood each time it beats, but you don't have very severe heart failure.

Last Updated: July 11, 2012
This information does not replace medical advice.  If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.

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