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Cardioversion is a procedure that is used to help return your heartbeat to its normal rhythm if you have arrhythmia (irregular heartbeat). This information focuses on the type of cardioversion called electrical or direct-current (DC) cardioversion. We will just refer to this as cardioversion throughout.

You will meet the doctor carrying out your procedure to discuss your care. It may differ from what is described here as it will be designed to meet your individual needs.

Animation - how the heart works

About cardioversion

Cardioversion is a procedure that uses an electric shock delivered from a defibrillator to restore your heart rhythm to normal if you have arrhythmia. Arrhythmia is caused by faulty electrical signals in your heart. There are different types of arrhythmia that can be treated with cardioversion. These include atrial fibrillation and ventricular tachycardia.

Ventricular tachycardia can be life-threatening, so cardioversion is often done urgently to correct your heart rhythm.

For other types of arrhythmia, cardioversion is usually given if your arrhythmia has lasted longer than 48 hours but less than a week. However, it can be difficult to know how long you have had your arrhythmia because in many people there are no symptoms.

Cardioversion isn’t suitable for everyone. It will depend on how long you have had arrhythmia for, your general symptoms and your medical history.

What are the alternatives to cardioversion?

There are many other treatments available to help regulate your heart's rhythm. Some are listed below.

  • Antiarrhythmic medicines – usually given as tablets – can help to control your heart rate and rhythm, but these may take several days or weeks to have an effect.
  • Ablation – this is a procedure in which tissue that may be disrupting the electrical signals in your heart is removed by freezing or burning it away.
  • Having a pacemaker fitted – a pacemaker is a device used to regulate your heartbeat. You may need to have a pacemaker fitted if your natural pacemaker isn't working properly.

Your doctor will advise which treatment is most suitable for you.

Preparing for cardioversion

Your doctor will explain how to prepare for your cardioversion.

If you need to have cardioversion urgently, your doctor will give you an anticoagulant medicine, such as heparin. This is often given intravenously, which means you will have a drip inserted into a vein in your hand or arm to give you the medicine. You may also need to have a transoesophageal echocardiogram to scan for blood clots in your heart.

If you have had arrhythmia for more than 48 hours, your doctor will plan your cardioversion at least three weeks in advance. This means there is enough time for any medicines your doctor may prescribe you to work properly. Your doctor may prescribe:

  • anticoagulant medicines – these help to stop your blood clotting (usually warfarin is used)
  • antiarrhythmic medicines – to help regulate your heart's rhythm

You're likely to have the following hospital tests before cardioversion.

  • Blood tests – to check your blood count, how well your kidneys work and how well your blood clots.
  • Electrocardiogram (ECG) – this measures the electrical activity in your heart to see what your heart rhythm is.
  • Echocardiogram – this is an ultrasound scan of your heart, which provides a clear image of your heart muscles and valves to show how well your heart is working.
  • Transoesophageal echocardiogram – this uses an ultrasound sensor passed into your oesophagus (the pipe that goes from your mouth to your stomach) to take a scan of your heart. It's done if you're unable to take anticoagulant medicines or if you have only developed arrhythmia within the last few days.

Cardioversion is routinely done as an outpatient or day case, under general anaesthesia. This means you will be asleep during the procedure and can usually go home the same day.

If you're having a general anaesthetic, you will be asked to follow fasting instructions. This means not eating or drinking, typically for about six hours beforehand. However, it’s important to follow your doctor’s advice.

Your doctor will discuss with you what will happen before, during and after your procedure, and any pain relief you might need. This is your opportunity to understand what will happen, and you can help yourself by preparing questions to ask about the risks, benefits and any alternatives to the procedure. This will help you to be informed, so you can give your consent for the procedure to go ahead – you may be asked to sign a consent form.

What happens during cardioversion?

Cardioversion usually takes five to 10 minutes after you’re given the general anaesthetic. Once you’re asleep, your doctor will give you a brief, controlled electric shock to your heart, usually through two pads placed on your chest that come from a defibrillator device.

Your heart rate and rhythm is monitored throughout the procedure, so your doctor can see immediately if the procedure has reset your heart to its normal rhythm.

Your doctor may give you up to two more electric shocks to reset your heart if the first attempt is unsuccessful.

What to expect afterwards

You will need to rest until the effects of the anaesthetic have passed. This will likely be less than an hour.

Your nurse will regularly check your heart rate and blood pressure. You will be able to go home once your heart rhythm is stable and you have fully recovered.

Your doctor will prescribe anticoagulant and antiarrhythmic medicines for you to take at home. It’s important to continue taking anticoagulants for at least one month after cardioversion.

You will usually be given a date for a follow-up appointment before you go home.

You will need to arrange for someone to drive you home. After general anaesthesia, you should try to have a friend or relative stay with you for the first 24 hours. General anaesthesia temporarily affects your co-ordination and reasoning skills, so you must not drive, drink alcohol, operate machinery or sign legal documents for 24 hours afterwards. If you're in any doubt about driving, contact your motor insurer so that you're aware of their recommendations and always follow your doctor's advice.

Contact your GP if you feel any changes in your heartbeat. If your arrhythmia has come back after you have had cardioversion, you may be able to have another cardioversion or alternative treatments to restore it – however, your doctor probably won't be able to give this to you straight away. For more information, see our frequently asked questions.

What are the risks?

Cardioversion is commonly performed and generally safe. However, in order to make an informed decision and give your consent, you need to be aware of the possible side-effects and the risk of complications.

As with every procedure, there are some risks associated with cardioversion. We have not included the chance of these happening as they are specific to you and differ for every person. Ask your doctor to explain how these risks apply to you.


Side-effects are the unwanted, but mostly temporary effects you may get after having the procedure, for example, feeling sick as a result of the general anaesthetic. After having cardioversion, the skin on your chest may feel a little sore where the shock was administered.

Cardioversion can cause a temporary drop in blood pressure, so you may have a headache or feel dizzy.

The antiarrhythmic medicine amiodarone can cause problems with your thyroid gland, lungs and liver, and may make your skin very sensitive to sunlight. If you're prescribed amiodarone, you will have regular check-ups and will need to wear sunscreen and cover up in the sun more than usual.


Complications are when problems occur during or after the procedure.

The most common complication of cardioversion is failure to restore your normal heart rhythm. The success of cardioversion depends on your medical condition. Research shows cardioversion immediately restores the heart's normal rhythm in nine out of 10 people with arrhythmia. However, some people find that their arrhythmia returns again within a few days, and up to half of people treated with cardioversion have arrhythmia again within the first year. If your arrhythmia does return after treatment, you will usually have to take antiarrhythmic medicines for four weeks before and four weeks after having a repeat cardioversion.

There are other possible complications of cardioversion. You could have an unexpected reaction to the anaesthetic. This is a problem for any procedure where anaesthesia is required and isn’t specifically related to cardioversion. You will be given medicines to help if this happens, but it’s extremely uncommon for such a short procedure.

You may develop other problems with your heart rhythm during cardioversion, for example, your heart may beat unusually slowly or fast. You will be given medicines to help if this happens.

There is an extremely small risk of having a heart attack or stroke after cardioversion. This happens when a blood clot which has formed in your heart is released during cardioversion, and then blocks the blood vessels in your heart or brain. Blood clots are more likely to form if you have had arrhythmia. You will be given anticoagulant medicines before your procedure to reduce your risk of blood clots forming. You will be advised to continue taking anticoagulant medicines for at least four weeks after your procedure to reduce blood clot formation.


Produced by Louise Abbott, Bupa Health Information Team, October 2012.

For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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