Expert reviewer Dr Matthew Wright, Consultant Cardiologist and Electrophysiologist
Next review due August 2023

Cardioversion is a procedure that helps to get your heart’s rhythm back to normal if it’s beating 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 don’t work properly. Cardioversion uses an electric shock, delivered from a machine called a defibrillator, to get your heart’s rhythm back to normal. You’ll be asleep, with a general anaesthetic, or heavily sedated for the procedure.

Cardioversion can treat different types of arrhythmia, including:

Cardioversion usually works well, but it 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 get ready for it. Your doctor will make all of the preparations.

Your doctor will give you a medicine that stops your blood clotting (called an anticoagulant). You’re likely to have this through a drip 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. An ultrasound sensor is put 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 before the procedure. They may prescribe:

  • oral anticoagulant medicines– you take these as tablets to help stop your blood clotting
  • anti-arrhythmic medicines – these help to control your heart’s rhythm, which means the cardioversion is more likely to work

There is more information about anticoagulant and anti-arrhythmic medicines in our FAQs section.

You may have some hospital tests before your cardioversion. These will help your doctor decide whether cardioversion is right for you. These include.

  • 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 often done as a day-case procedure. This means you’ll probably be able to go home on the same day. You may not be allowed to eat for at least six hours before your cardioversion. However, you might be able to drink clear fluids up until two hours before. If you’re asked to follow fasting instructions before your cardioversion, follow your doctor’s advice.

Don’t put any powders, lotions or creams on your chest for 24 hours before your cardioversion. These can cause problems with the paddles used for passing the electrical current. If you have any chest hair, the doctor or nurse will shave this away from where the paddles will be placed. They’ll also make sure your skin is dry.

Your surgeon will discuss with you what will happen before, during and after your surgery. If you’re unsure about anything, don’t be afraid to ask. No question is too small. It’s important that you feel fully informed so you feel happy to give your consent for the operation to go ahead. You’ll be asked to do this by signing a consent form. Remember you’ll need someone to drive you home and stay with you after your cardioversion. 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. Chemical (or pharmacological) cardioversion is when your doctor gives you medicines to bring back your regular heart rhythm. Ask your doctor if this could be an option for you, and what it involves.

Your doctor may suggest something else to help regulate your heart’s rate and rhythm. The best one for you will depend on the type of arrhythmia you have and your general health.

  • Anti-arrhythmic medicines – you have to keep taking these tablets to help 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 procedure involves putting a thin tube through one of your veins (often in your groin) into your heart. The area of your heart muscle that’s causing the abnormal heart rate is then heated or frozen to form a scar. This scar doesn’t conduct electricity so it stops any wrong electrical signals that your heart’s making.
  • Having a pacemaker fitted – this device can regulate your heartbeat.

Speak to your doctor about whether any of these treatment options are right for you.

What happens during cardioversion?

You may be worried about having an electric shock to your heart, but cardioversion is a very safe procedure. Your heart doesn’t stop during the procedure. The electric shock makes your heart cells contract at the same time, which resets your heart rate and rhythm back to normal.

The whole procedure usually takes 10 to 30 minutes. You’ll be given a sedative or a light general anaesthetic first. Having a general anaesthetic will mean you’re asleep during the procedure, while a sedative will make you very sleepy. Then your doctor will give your heart a brief, controlled electric shock. To do this, they’ll usually put two pads on the front and back of your chest. These pads are linked to a defibrillator machine.

Your doctor will monitor your heart rate and rhythm during the procedure. This means they can see straightaway 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 properly.

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 anaesthetic or sedation has worn off.

The doctors and nurses will use an ECG machine to keep an eye on your heartbeat. Once they’re happy you’re recovering well and you feel ready, you can get out of bed and walk around. Arrange for someone to drive you home and keep an eye on you that day.

General anaesthesia can make it harder to coordinate your movements and to think clearly. So, it’s a good idea to ask someone to 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. 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.

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 which creams you could use if the paddles have made your skin a little sore.

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

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

Contact your GP if you notice any changes in your heartbeat or your symptoms come back. If your abnormal heart rhythm comes back after you’ve had cardioversion, you may need more treatment.

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What are the side-effects of cardioversion?

Side-effects are the unwanted, but mostly temporary, effects you may get after having a procedure. After your cardioversion you may:

  • feel sick from the general anaesthetic
  • notice the skin on your chest feels a bit sore where you had the shock
  • have a headache or feel dizzy if your blood pressure dropped for a while during the procedure

Some of the medicines you’re given to take before or after your cardioversion can have some side-effects too. Ask your doctor about any risks or side-effects of any medicines they recommend for you.

What are the risks of cardioversion?

Cardioversion is usually a safe procedure, but sometimes it can cause complications.

  • You may have an unexpected reaction or allergy to the anaesthetic or sedation, which needs to be treated.
  • Cardioversion may cause other problems with your heart rhythm. Most of these will settle over time and don’t need to be treated.
  • You may get a blood clot. Having a blood clot after cardioversion can make you more likely to have a stroke. But you’ll be given anticoagulant medicines before and after your procedure to reduce the chances of this happening.

Frequently asked questions

  • Taking an anticoagulant medicine means you’re less likely to get a blood clot after cardioversion. You’ll usually need to take an anticoagulant medicine for at least three or four weeks before and after your cardioversion.

    Having an irregular heartbeat may increase your chances of having a blood clot. This is because some of the blood in your heart may not be pushed out with every beat. The blood that stays in your heart may then be more likely to clot and this could cause a stroke.

    If your cardioversion is urgent, you’re likely to be given an anticoagulant through a vein in your hand or arm first. You may have a scan too, to check for blood clots in your heart, before the cardioversion can go ahead.

  • There’s always a chance your heartbeat won’t be corrected by the shock.

    How well cardioversion works 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 the right option for you.

    Some people find their arrhythmia comes back again after 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 comes back after your cardioversion, your doctor may recommend you have the procedure again, or they may recommend a different treatment.

  • Anti-arrhythmic medicines help to regulate your heart rate and rhythm. Your doctor may prescribe these medicines if cardioversion doesn’t work or to stop your arrhythmia coming back after treatment.

    Cardioversion helps to reset your heart’s rhythm when it goes wrong, but often an arrhythmia can come back. You may need to take anti-arrhythmic medicines every day for a long time. Or, you may be given a tablet to take only if you get symptoms, which means you don’t need to take it 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, including an irregular heartbeat, can still fly.

    Your doctor may need to think about whether:

    • you've recovered fully from your procedure
    • you still have an irregular heartbeat, and if so, what type
    • your irregular heartbeat is being controlled properly

    If you have ongoing heart problems and your doctor says you can travel, let your airline know about your condition. They can make sure any extra safety measures are in place, just in case you need them. Also, check your travel insurer will cover you.

    Your doctor can also let you know about any extra precautions you should take. Long journeys can make you more likely to get a blood clot. Wearing compression stockings may help to lower your risk.

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  • Reviewed by Abbey Stanford, Specialist Health Editor, August 2020
    Expert reviewer Dr Matthew Wright, Consultant Cardiologist and Electrophysiologist
    Next review due August 2023