Expert reviewer, Mr Mark Yeatman, Consultant Cardiothoracic Surgeon
Next review due January 2021

Cardioversion is a procedure to help return your heart’s rhythm to normal if it’s beating irregularly (unevenly) or too fast. Here we look at a type of cardioversion called electrical or direct-current (DC) cardioversion.

About cardioversion

An abnormal heart rhythm is called an arrhythmia. It happens when the normal electrical signals in your heart become faulty. Cardioversion uses an electric shock, delivered from a machine called a defibrillator, to restore your heart’s rhythm to normal. You’ll be asleep, with a general anaesthetic, or heavily sedated for the procedure.

There are different types of arrhythmia that can be treated with cardioversion. These include atrial fibrillation, atrial flutter and ventricular tachycardia. Cardioversion isn’t suitable for everyone. Whether it’s right for you will depend on how long you’ve had arrhythmia, your symptoms and your medical history.

Preparing for cardioversion

Your doctor will explain how to prepare for your cardioversion.

Preparing for an urgent cardioversion

If you need to have cardioversion urgently, there’s nothing you need to do to prepare. Your doctor will make all the preparations.

Your doctor will give you a medicine to stop your blood clotting (an anticoagulant). You’re likely to receive this through a drip inserted into a vein in your hand or arm.

You may also have a scan called a transoesophageal echocardiogram to check for blood clots in your heart. To do this, a device called an ultrasound sensor is passed into your oesophagus (gullet) to look at your heart. Your oesophagus is the pipe that goes from your mouth to your stomach. You’ll have the cardioversion as soon as your doctor has checked it’s safe to go ahead.

Preparing for a planned cardioversion

If your cardioversion is planned, there’s plenty of time for you to take any medicines your doctor prescribes beforehand. They may prescribe:

  • oral anticoagulant medicines – these are taken as tablets. They help to stop your blood clotting (eg warfarin)
  • anti-arrhythmic medicines – these help to control your heart’s rhythm, making it more likely that cardioversion will work

You may have some hospital tests before your cardioversion. These will help your doctor decide whether cardioversion is suitable for you. Tests you might have are explained below.

  • Blood tests – for example, to check how well your blood clots.
  • An electrocardiogram (ECG) – this measures the electrical activity in your heart and its rhythm.
  • An echocardiogram – this is an ultrasound scan of your heart. It provides a clear image of your heart muscles and valves, and shows how well your heart is working.
  • A transoesophageal echocardiogram – see above for a description of this test.

Cardioversion is usually done as a day-case procedure, which means you’ll probably go home the same day. You may be asked to follow fasting instructions beforehand. This means not eating or drinking, typically for at least eight hours before your cardioversion. Follow your doctor’s advice about fasting.

Don’t put any powders, lotions or creams on your chest for 24 hours before your cardioversion treatment. They can cause problems with the paddles used for passing the electrical current.

Your doctor will explain what will happen before, during and after your procedure. This is your chance to understand what will take place. You may want to ask questions about the risks, benefits and any alternatives to the procedure. Writing questions down before your appointment can be helpful, as it might be hard to remember all your questions on the day. You don’t have to go ahead with the procedure if you decide you don’t want it. Once you understand the procedure and if you agree to have it, your doctor will ask you to sign a consent form.

When planning ahead for your procedure, remember you’ll need someone to drive you home and stay with you afterwards. This is because you’ll have had a general anaesthetic or a sedative.

What are the alternatives to cardioversion?

Our information here is about electrical, or DC cardioversion. There’s an alternative called chemical (or pharmacological) cardioversion where your doctor gives you medicines to bring back your regular heart rhythm. Ask your doctor if this might be an option for you in your particular circumstances, and what it involves. 

There may be alternatives to cardioversion available to help regulate your heart’s rate and rhythm. Which ones might be suitable for you will depend upon the type of arrhythmia you have and your general health. Some alternative treatments are listed below.

  • Anti-arrhythmic medicines – these are usually given long term as tablets and can help to control your heart’s rate and rhythm. They can work as well as cardioversion for treating most arrhythmias. Your doctor may also offer you anticoagulant medicines to prevent blood clots.
  • Ablation – this is a procedure that’s different to cardioversion. It involves creating a lesion in a small part of your heart muscle, so forming a scar. It aims to stop any faulty electrical signals that your heart is making. It’s often done by placing a thin tube through one of your veins (often one in your groin) into your heart to freeze a small area. The heart tissue that’s causing the problem can then be treated via this tube.
  • Having a pacemaker fitted – this is a device used to regulate your heart beat.

Ask your doctor about the pros and cons of these treatments for arrhythmia. They will discuss with you which treatment options are most suitable for you. 

What happens during cardioversion?

The thought of having an electric shock to your heart might be worrying, but the procedure is short and very safe.

The whole cardioversion procedure usually takes between about 10 and 30 minutes. Just beforehand, you’ll be given a sedative or a light general anaesthetic. Having a general anaesthetic will mean you’re asleep during the procedure, whereas a sedative will make you very drowsy. Once this has taken effect, your doctor will give your heart a brief, controlled electric shock. To do this, they’ll usually use two pads that come from a defibrillator device placed on the front and back of your chest.

Your doctor will monitor your heart rate and rhythm during the procedure. This means they can immediately see whether the procedure has reset your heart to its normal rhythm. Your doctor may give you one or two more electric shocks to reset your heart if the first one doesn’t work fully.

What to expect afterwards

When you wake up from your cardioversion, you may feel tired or unsteady. You’ll need to rest for a few hours until the effects of the anaesthetic or sedation have passed.

An ECG machine is used to keep an eye on your heart beat while you recover. Once the doctors and nurses looking after you are happy and you feel ready, you can get out of bed and walk around. You’ll be able to leave hospital once your heart rhythm is stable. Be sure to arrange for someone to drive you home and keep an eye on you that day.

You’ll probably be given a date for a follow-up appointment before you leave. Your doctor may prescribe anticoagulant medicines for you to take at home.

General anaesthesia can make it harder to coordinate your movements and to think clearly. So, it’s a good idea to have someone stay with you for the first 24 hours, in case you become unwell. Don’t drive, drink alcohol, operate machinery or sign legal documents during this time.

Recovering from cardioversion

It’s a good idea to take it easy for a few days after your procedure. Your doctor will give you advice about what to do when you’re at home. This may include what creams you could use if the paddles have left your skin a little sore.

You’ll also be given advice on when you can go back to work and begin exercise again. This will differ from person to person.

It’s important you keep taking anticoagulants for as long as your doctor recommends. This is to reduce your risk of getting a blood clot. If you have any queries about your medicines, or how to take them, ask your pharmacist.

Contact your GP if you notice any changes in your heart beat or your symptoms return. If your arrhythmia comes back after you’ve had cardioversion, you may need more treatment. 

 Worried about your heart health?

Get a picture of your current health and potential future health risks with one of our health assessments. Find out more today. Find out more about health assessments >

 Worried about your heart health?

What are the side-effects of cardioversion?

Side-effects are the unwanted, but mostly temporary, effects you may get after having a procedure. For example, you may feel sick after the general anaesthetic. After having cardioversion, the skin on your chest may feel slightly sore from where the shock was given to you.

Cardioversion can cause your blood pressure to temporarily drop, so you may have a headache or feel dizzy.

You might also find that the medicines you’re given to take before or after your cardioversion have side-effects. Ask your doctor about any risks or side-effects of the particular medicines they recommend for you.

What are the risks of cardioversion?

Doctors consider cardioversion to be a safe procedure, but remember that all medical procedures carry some risk of complications, however small. Complications are problems that occur during or after a procedure.

The possible complications of cardioversion include the following.

  • You may have an unexpected reaction to the anaesthetic or sedation. You’ll be given treatment to help if this happens, but it’s extremely rare.
  • You may develop other problems with your heart rhythm during cardioversion. These are uncommon though and most don’t need treatment.
  • There’s a very small risk of having a stroke after cardioversion. A stroke happens when a blood clot which has formed in your heart is released during cardioversion. This then blocks a blood vessel in your brain. You’ll be given anticoagulant medicines before and after your procedure to reduce this risk.

Frequently asked questions

  • Anticoagulant medicines help to reduce your risk of developing a blood clot.

    If you have an arrhythmia, it means you have an irregular heartbeat. As a result, some of the blood in your heart might not be pushed out of your heart with each beat. The blood that remains may be more likely to clot. If a clot breaks off and goes to your brain, it could cause a stroke.

    Your doctor will usually prescribe an anticoagulant medicine (such as warfarin) to help reduce your risk of developing a blood clot. You’ll normally be asked to take this for at least three or four weeks before and after having cardioversion.

    If you have urgent cardioversion, you’re likely to be given an anticoagulant through a vein in your hand or arm. This helps prevent any blood clots forming in your heart. You may have a scan too, to check for blood clots in your heart.

  • Cardioversion usually works well to correct arrhythmia, at least in the short-term. Up to nine out of 10 people with atrial fibrillation will get back to a normal rhythm after the procedure. However, there’s a chance your heart beat will not be corrected by the shock.

    The likelihood of cardioversion working varies from person to person. It may depend on the type of arrhythmia you have, what’s causing it and how long you’ve had it. Your doctor will only recommend cardioversion if they believe it’s a good option for you in your particular circumstances. You can ask them to explain why.

    Some people find that their arrhythmia returns again within a few days, weeks or months. Up to half of people treated with cardioversion for atrial fibrillation get the condition again within a year.

    If your arrhythmia returns after your cardioversion, your doctor may recommend you have the procedure again, or they might recommend a different treatment. 

  • Medicines to help regulate your heart rate and rhythm are known as anti-arrhythmic medicines. They’re sometimes prescribed if cardioversion doesn’t work or to prevent your arrhythmia coming back after treatment.

    Cardioversion helps to reset your heart’s rhythm when it goes wrong, but sometimes an arrhythmia can return days, weeks, or months afterwards. Your doctor may recommend you take anti-arrhythmic medicines to help prevent this happening. If you have atrial fibrillation, for example, you’re less likely to get an arrhythmia again if you take an anti-arrhythmic medicine after your cardioversion.

    For some people, it may be possible to have a tablet to take only if you get symptoms. This means you wouldn’t need to take the medicine regularly. This is sometimes called ‘pill in the pocket’ therapy.

    Whether your doctor recommends an anti-arrhythmic medicine for you, and which one they recommend, will depend on your symptoms and general health.

  • You’ll need to check with your doctor whether or not it’s safe for you to travel by air if you’ve recently had cardioversion. Many people with heart problems can still fly in an aeroplane. For example, if you have an arrhythmia but it’s being well controlled, you’ll probably still be able to fly.

    Things your doctor may take into account when advising whether it’s safe for you to travel by air include:

    • whether you’ve recovered fully from your procedure
    • whether you still have an arrhythmia, and if so, what type

    If you have ongoing heart problems and your doctor gives you the okay to travel, let your airline know about your condition. They can make sure any extra safety measures are in place that you might need. Also, check with your travel insurer that you’ll be covered.

    Your doctor can also let you know about any extra precautions you should take. For example, long journeys can increase your risk of having a blood clot, so wearing compression stockings can reduce this risk.

Did our information help you?

We’d love to hear what you think. Our short survey takes just a few minutes to complete and helps us to keep improving our health information.

About our health information

At Bupa we produce a wealth of free health information for you and your family. This is because we believe that trustworthy information is essential in helping you make better decisions about your health and wellbeing.

Our information has been awarded the PIF TICK for trustworthy health information. It also complies with the HONcode standard and follows the principles of the The Information Standard.

The Patient Information Forum tick  This website is certified by Health On the Net Foundation. Click to verify.

Learn more about our editorial team and principles >

Related information

    • Defibrillation and cardioversion. Medscape., updated 14 April 2016
    • Synchronized electrical cardioversion. Medscape., updated 22 September 2016
    • Defibrillation and cardioversion. PatientPlus., last checked 24 March 2017
    • Atrial fibrillation: the management of atrial fibrillation. National Institute for Health and Care Excellence (NICE)., August 2014
    • Kirchhof P, Benussi S, Kotecha D, et al. 2016 ESC Guidelines for the management of atrial fibrillation developed in collaboration with EACTS. Eur Heart J 2016; 37(38):2893–962. doi:10.1093/eurheartj/ehw210
    • Practical procedures. Oxford handbook of Cardiology (online). Oxford Medicine Online., published May 2012
    • Cardiovascular medicine. Oxford Handbook of Clinical Medicine (online). Oxford Medicine Online., published September 2017
    • Practical procedures. Oxford Handbook of Clinical Medicine (online). Oxford Medicine Online., published September 2017
    • Cardioversion. British Heart Foundation., accessed 17 January 2018
    • Abnormal heart rhythms. British Heart Foundation., accessed 17 January 2018
    • Echocardiogram. British Heart Foundation., accessed 17 January 2018
    • Ablation. British Heart Foundation., accessed 17 January 2018
    • Heart rhythms. British Heart Foundation 2017.
    • Travel and your heart. British Heart Foundation 2017.
    • Cardioversion. American Heart Association., updated 21 December 2016
    • Understand your risk of excessive clotting. American Heart Association., updated 2 November 2015
    • Why arrhythmia matters. American Heart Association., updated 21 December 2016
    • Gorenek B. Cardioversion in atrial fibrillation described. E-journal of the ESC Council for Cardiology Practice 2012; 11(6)
    • Fitness to fly for passengers with cardiovascular disease. British Cardiovascular Society 2010.
    • Personal communication, Mr Mark Yeatman, Consultant Cardiothoracic Surgeon, February 2018
  • Reviewed by Dr Kristina Routh, Freelance Health Editor, January 2018
    Expert reviewer, Mr Mark Yeatman, Consultant Cardiothoracic Surgeon
    Next review due January 2021