This is essentially a large pacemaker, but has certain additional features which require it to be a little larger than a standard pacemaker. It comprises a small box (‘Generator’), connected to one, two or three wires (‘leads’) which pass through the vein behind the collarbone into the heart. The ICD may have a single lead into either the top (‘right atrium’) or bottom (‘right ventricle’) chamber of the heart, or a lead in both. A special type of ICD, called a ‘biventricular ICD’ (‘CRT-D’) has three leads and is used for patients whose hearts are at risk of potentially dangerous fast heart rhythms and who have heart failure with certain features. Because it is a little bigger than a standard pacemaker, it is often buried under the chest muscle on the left hand side. Because of this, the procedure is often performed under a general anaesthetic. The procedure is done through an incision about 4-5cm, or 1 ½-2 inches, just below the collarbone. An ICD has the capability to detect if the patient’s heart goes into a fast rhythm which might make the patient feel unwell, black out, or even put their life at risk. The ICD will then either attempt to pace the heart very quickly to stop the rhythm, or shock the heart internally to break the rhythm, depending on the way it is programmed. There is a small risk of complications, such as bleeding, infection, puncturing the lung behind the vein (behind the collarbone), and one of the leads displacing. The risk of any of these is usually no more than 1 in 100. The patient will need to have the ICD checked regularly. This is done by simply putting a header (which looks a little like a computer ‘mouse’) over the skin above the ICD. The header is connected to a programmer which retrieves information about how the heart has been behaving since the last check. Changes can also be made to the settings of the ICD in this way. Patients are usually seen one month after the procedure, and then every three months after that. Many patients with ICDs now take advantage of ‘Home Monitoring’ systems. This involves taking home a special box which plugs into the patient’s home telephone line. The box then wirelessly connects with the ICD when the patient is close by, and sends the information about the heart down the telephone line to the patient’s doctors. This has proved extremely useful in allowing patients to avoid frequent repeated visits to hospital, simply to confirm that all is well!