An Implantable Cardioverter Defibrillator (ICD) is a remarkable device that briefly passes an electric current through the heart to control arrhythmias. It is implanted in the body surgically, sometimes underneath the right chest muscle (sub-muscular implantation) or just beneath the skin (subcutaneous implantation).

          The ICD consists of a pulse generator and one or more leads. In addition a small computer and a long life Lithium battery are in the sealed case

          The following diagram shows where the ICD is typically implanted and the one or more leads normally threaded through a vein and guided to the heart chamber.

          The  main manufacturers of ICDs web sites have a wealth of information specifically aimed at patients with such devices. See the Links page for further information.

          You will have been supplied with a manufacturers information pack after your device has been implanted. In addition there are also other sources of information available from the British Heart Foundation, in particular the booklet Health Information Series Number 19 and the Arrhythmia Alliance which also has an ICD Patient Information booklet which may be downloaded from their site.

Why might you need an ICD?

           Normally the heart has a natural pacemaker called the sinoatrial node that helps the heart beat steadily. An electrical current starts in one of the upper chambers (atria) and goes through the heart into the lower chambers (ventricles). If you have heart rhythm problems, an ICD may be fitted to help control the hearts natural pacemaker.

          When the heart beats too fast (tachycardia) and when the problem begins in the bottom chamber of the heart, it’s called ventricular tachycardia. This makes the heart pump blood less efficiently and you may feel your heart pounding. You may feel dizzy or faint. If not treated properly, ventricular tachycardia can be life threatening.

          When a ventricular arrhythmia (irregular heartbeat) becomes very fast and irregular, it’s called ventricular fibrillation. The heart just quivers and no blood is pumped to the body or the brain. A person with ventricular fibrillation usually passes out very quickly. Unless treated in a few minutes, ventricular fibrillation causes death. In people without an ICD, ventricular fibrillation is treated with an external defibrillator. Many TV medical dramas regularly depict this happening. This is accomplished by giving the heart a large electric shock through paddles on the outside of the chest and causes the heart to go back to its normal rhythm.

          Unfortunately ventricular fibrillation can occur without warning and often treatment cannot be given in time. An ICD may be fitted because your doctor thinks you are at high risk of having ventricular fibrillation. An ICD can quickly recognise and stop ventricular fibrillation.

How does the ICD work?

          The ICD constantly monitors your heart rhythm through the leads into the heart. The ICD can do several things.

• Pacing. If you have ventricular tachycardia that isn’t too severe, the ICD can deliver several pacing signals in a row. When these signals stop, the heart may go back to normal rhythm.
• Cardioversion. If the pacing doesn’t work, cardioversion send a mild electric shock to the heart to stop the fast heart beat.
• Defibrillation. If ventricular defibrillation is detected, a stronger shock is sent. This stronger shock can stop the fast rhythm and help the heart beat go back to normal.
• Pacemaker. The ICD can also be used when the heart beats too slow, (bradycardia). It can act like a pacemaker and bring your heart up to normal.

How will an ICD affect my lifestyle?

          Your doctor may want you to limit your activities for the first few weeks after your procedure. Then you can slowly go back to your normal lifestyle.

         You will also be advised to stay away from certain types of machine that could interfere with your ICD. The manufacturers booklet given to you will explain these limitations as indeed will the previously mentioned literature available from the British Heart Foundation and the Arrhythmia Alliance.

Having a defibrillator fitted.

          An excellent booklet produced by the British Medical Journal informs you about the procedure to implant an ICD in your chest to help your heart beat normally. The booklet explains how the procedure is done, how the ICD can help you, what the risks are and what to expect afterwards. To view the booklet in PDF format, click here. You may then print the booklet or save it on your computer.

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