What is an ICD?

ICD stands for Implantable Cardioverter Defibrillator.

It is made up of a small, slim, box shaped device which contains a battery and electronic circuits. The device is connected to your heart by one or more wires (called leads).


The leads are passed along a blood vessel to your heart and the ICD box is usually implanted under the skin in your upper chest, near your collar bone. The ICD can recognise and monitor your heart rhythm and can give you some treatments if needed. It also stores information about your heart rate and rhythm which can be accessed when you come to the clinic for follow-up.


How the heart works normally

The heart is a muscle, its function is to pump blood and oxygen around you body to all of your vital organs. It has four chambers, two at the top (the right and left atrium) and two at the bottom (the right and left ventricles). The heart also has an electrical system, which sends impulses (beats), through the heart causing it to contract and pump blood around the body. Each normal heartbeat begins in the natural pacemaker of the heart (the Sinus Node or SA node) which lies at the top of the right atrium. It then travels across the two top chambers and down through a small junction box (the atrio-ventricular or AV node) which lies between the upper and lower chambers. It then spreads across the bottom chambers causing the heart to contract and pump.


Sometimes the electrical system in your heart does not work as well as it should. This can cause your heart to beat too quickly. The ICD can stop fast heart rhythms that start in the ventricles, the bottom two chambers of the heart. This fast heart rhythm is called ventricular tachycardia or VT. This can sometimes start after a heart attack or in people who have angina. There are several other reasons that you may benefit from having an ICD, even if you have never had an abnormal heart rhythm.

Some people can have an even faster, irregular heart rhythm called ventricular fibrillation or VF. This is life threatening if it is not treated quickly with analectic shock delivered to the heart.


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