Dr Simon Kennon MB ChB, FRCP, MD Consultant Cardiologist

ICD ("Defibrillator") Implantation

An ICD (or implantable cardioverter defibrillator) is a small device implanted in your chest which can be used to treat people with dangerously abnormal heart rhythms.

Abnormal heart rhythms (or arrhythmias) can cause your heart to beat too quickly, too slowly or in an irregular pattern. These heart rhythms can happen suddenly and unexpectedly and sometimes people die as a result. This is where an ICD can help: by monitoring your heart rhythm it can detect abnormalities and deliver electrical impulses to correct it where necessary.

How does it work?

The ICD is inserted just under your collar bone. It looks similar to a pacemaker and is a little bigger than a matchbox. An ICD has wires with electrodes that connect to one or more of your heart's chambers. The ICD continually monitors your heart rhythm and if it notices an abnormal heart rhythm, it can deliver high- or low-energy electrical pulses or shocks to the heart.

How is an ICD fitted?

ICDs are inserted under local anaesthetic, but with sedation, so you will feel very sleepy. It can take as little as one hour to insert the ICD, although the time it takes will depend on the type of device you're having.


You will usually stay overnight in hospital and your ICD will be checked thoroughly before you leave. Most people can return to normal activities, such as exercise, work and sex, soon after you recover from surgery. That said, your doctor may advise you to refrain from vigorous above-the-shoulder activities and strenuous exercise for a few weeks.


Implanting an ICD has some risks, but they are rare. They include:

  • Infection at the site where your ICD was implanted
  • Allergic reaction to the medications used during the procedure to implant your ICD
  • Swelling, bleeding or bruising where your ICD was implanted
  • Damage to the vein where your ICD leads are placed
  • Bleeding around your heart, which can be life-threatening
  • Blood leaking through the heart valve where the ICD lead is placed