What is cardioversion?

Cardioversion is a treatment for some types of cardiac arrhythmia (when your heart isn’t beating in its normal rhythm). The most common type of arrhythmia is called atrial fibrillation.  This means that the upper chambers in your heart are moving fast and aren’t contracting properly. The symptoms include dizziness, fainting, palpitations and a fluttering feeling in your chest. 

Cardioversion involves applying a controlled electric shock to your chest to reset your heart’s normal rhythm. Depending on how severe your symptoms are, cardioversion may be done shortly after you see your cardiologist about them. 

Alternatively, he or she may wait to see if your heart goes back to a normal rhythm on its own, or with the help of medicines. 

One of the reasons that cardiac arrhythmias are treated is because some types of arrhythmia can lead to a stroke. This is because blood may start to pool in the chambers of your heart, where it can form a blood clot. If this clot moves through the bloodstream to the brain, it could cause a blockage of the blood supply, leading to a stroke. 

Cardioversion is routinely done as an out-patient or day-case, with no overnight stay in hospital.  The procedure is usually done under general anaesthesia. This means you will go to sleep briefly and not feel anything during the procedure. 

Your cardiologist will explain the benefits and risks of having a cardioversion, and will also discuss the alternatives to the procedure. 

About cardioversion 

Before cardioversion, you will have an electrocardiogram (ECG). An ECG involves placing some sticky pads (electrodes) on your arms, legs and chest to measure the electrical impulses from your heart. Your cardiologist will use this to check whether your heartbeat has already returned to normal by itself. An ECG is totally painless. 

Once the anaesthesia has taken effect, you will be given a controlled electric shock. To do this, paddles with soft gel pads on them are placed on your chest.  Throughout the procedure, small electrodes on your chest monitor your heart’s rhythm so that your cardiologist can see whether or not the treatment is working. 

Your cardiologist can tell immediately if the procedure has reset your heart to its normal rhythm. If it has not been successful, your cardiologist may repeat the treatment once or twice more. 

The procedure usually takes up to 10 minutes. 

If the cardioversion has worked, you will immediately feel better. If it has not worked, you may need to stay in hospital overnight and have the procedure repeated the next day. Alternatively your cardiologist may arrange for you to come back at a later date for further treatment. 

After cardioversion it is possible that the skin on your chest may feel a little sore where the shock was administered – a bit like sunburn.  You may also have low blood pressure after cardioversion. This only lasts a few hours and your nurse will monitor your blood pressure at regular intervals. 

Cardioversion is a commonly performed and generally safe procedure. For most people, the benefits of having quick and effective treatment are much greater than any disadvantages. However, as with all medical procedures, there is an element of risk. 

Your cardiologist will be very experienced at performing this type of procedure but, even so, cardioversion does not always restore a normal heart rhythm. The success of cardioversion depends on your medical condition. 

Sometimes, cardioversion can trigger other arrhythmias (abnormal heart rhythms) or affect the way that your heart muscles work.  It is also possible that a blood clot may be dislodged from your heart during the procedure. This could travel to the lungs or elsewhere in the body. If the blood clot causes a blockage in the brain, this could result in a stroke. Your cardiologist will make sure that you are taking the most appropriate blood–thinning medicine to reduce this risk. 

If high energy shocks have been used, some parts of the heart tissue may die.  This is called myocardial necrosis.  Rarely, fluid may collect in your lungs after this cardioversion. This is called pulmonary oedema. 

The chance of complications depends on the exact type of arrhythmia your have, the type of treatment you are receiving, and other factors such as your general health. Ask your cardiologist to explain how these risks apply to you.


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