Cardioversion
Your health expert: Professor Mark Westwood, Consultant Cardiologist
Content editor review by Rachael Mayfield-Blake, Freelance Health Editor, November 2022.
Next review due November 2025.
Cardioversion is a procedure that helps to get your heart’s rhythm back to normal if it’s beating unevenly or too fast or slow. It can treat these abnormal heartbeats (arrhythmias) or atrial fibrillation (an irregular and abnormally fast heartbeat). There are different types of cardioversion – here we look at a type of cardioversion called electrical or direct-current (DC) cardioversion.
How the heart works
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Your heart is a muscular organ which lies in the centre of your chest.
It pumps blood containing oxygen from the lungs to the body and passes blood without oxygen back to the lungs to absorb more oxygen.
To do this effectively, your heart is divided into four compartments, or chambers.
There are two chambers on the right side of the heart, and two on the left. A valve lies at the exit of each chamber. The valves ensure that blood flows in one direction only.
The left atrium lies above the left ventricle, the two are separated by a valve called the mitral valve.
The right atrium is above the right ventricle, these two chambers are separated by the tricuspid valve.
The left atrium receives blood that contains oxygen from the lungs via the pulmonary veins. This blood then passes into the left ventricle, which pumps it into the aorta.
From the aorta the blood is passed to the different parts of the body.
The right atrium receives blood with little oxygen from the body, via the vena cava. This blood passes into the right ventricle, which pumps it into the pulmonary artery and back to the lungs to have oxygen added to it.
The valve at the exit of the left ventricle, the aortic valve stops blood passing back into the ventricle. The pulmonary valve at the exit of the right ventricle also stops blood flowing backwards.
This flow of blood doesn't happen automatically, it's driven by contractions of the heart muscle which are triggered by electrical impulses.
A pacemaker in the upper part of the right atrium, called the sinoatrial node, sends electrical impulses across the atria that cause them to contract. The impulses reach the atrioventricular node, which is between the right atrium and ventricle, and pass on to the atrioventricular bundle causing the ventricles to contract and send blood to the lungs and around the body.
These electrical impulses spread across the heart muscle to ensure it contracts in the correct sequence. Nerves supplying the heart change the rate at which impulses are sent across the heart muscle to meet the needs of the body.
Together the chambers, valves, vessels and electrical impulses enable blood to be pumped around the body effectively, so you get the oxygen you need.
About cardioversion
An abnormal heart rhythm is called an arrhythmia. It happens when the normal electrical signals in your heart don’t work properly and your heart beats too fast, too slow or irregularly. 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:
- atrial fibrillation
- atrial flutter
- ventricular tachycardia
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 the arrhythmia, your symptoms, and your medical history. Ask a doctor if it’s an option for you.
Preparation for cardioversion
Preparation for an urgent cardioversion
If you need to have cardioversion urgently, there’s nothing you need to do to get ready for it.
A 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 cardioversion as soon as your doctor has checked it’s safe to go ahead.
Preparation for a planned cardioversion
If your cardioversion is planned, there’s time for you to take any medicines your doctor prescribes before the procedure. They may prescribe:
- oral anticoagulant medicines – these are tablets that 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
- 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.
There’s more information about anticoagulant and anti-arrhythmic medicines in our FAQs section.
You may have some tests in hospital before cardioversion. These will help your doctor decide whether cardioversion is right for you. These might include the following.
Cardioversion is often done as a day-case procedure. This means you’ll probably be able to go home on the same day but it’s possible you may need to stay in hospital overnight. You usually can’t eat or drink for up to six hours before a cardioversion but 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 where the paddles will go, a doctor or nurse may shave it off.
Your doctor will discuss with you what will happen before, during and after your procedure. 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 procedure to go ahead.
Ask a friend or relative to drive you home and stay with you after your cardioversion (see the aftercare section below).
Cardioversion procedure
Cardioversion usually takes up to 30 minutes. You’ll have a sedative or a short-acting general anaesthetic first so you’ll be asleep during the procedure.
Your doctor will put two pads (electrodes) on the upper right and lower left of your chest, or on the front and back of your chest. These pads are linked to a defibrillator machine. They’ll give your heart a brief, controlled electric shock in time with the beat of your heart. The electric shock works across your whole heart at once to re-set your heart rate and rhythm back to normal.
Your doctor will monitor your heart rate and rhythm during the procedure. This is so 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.
Aftercare following cardioversion
When you wake up after cardioversion, you may feel tired or unsteady. You’ll need to rest for a few hours until the anaesthetic or sedation has worn off and your hospital team can see if you can go home.
The doctors and nurses will use an ECG machine to monitor your heartbeat. Once they’re happy you’re recovering well and you feel ready, you can get out of bed and walk around.
You’ll probably be given a date for a follow-up appointment before you leave. Your doctor will usually prescribe anticoagulant and anti-arrhythmia medicines for you to take at home.
Arrange for someone to drive you home. General anaesthesia and sedation 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. Don’t drive, look after children, cook, drink alcohol, operate machinery or sign legal documents during this time.
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Recovery following cardioversion
Take it easy for a few days after your procedure. Your doctor will give you advice about what to do. For example, you may need to use creams if the paddles have made your skin a little sore (like you have sunburn). Your doctor will usually tell you what to use.
They’ll also give you advice about when you can go back to work and start exercising again.
It’s important to keep taking any medicines 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 a pharmacist.
You’ll have check-ups with your doctor after cardioversion. The first will be around three months after cardioversion and then every year.
Contact your GP if you notice any changes in your heartbeat, or if your symptoms come back. If your abnormal heart rhythm comes back after you’ve had cardioversion, you may need more treatment. Your doctor may recommend you have cardioversion again – you can have cardioversion as many times as you need. But usually after two or three cardioversions, your doctor may recommend that you have a different treatment, such as medicines or ablation (see the section on alternatives to cardioversion).
Side-effects of cardioversion
Side-effects are unwanted, but mostly temporary, effects you may get after having a procedure. After cardioversion you may:
- notice your chest feels a bit sore where you had the shock
- have some burns on the skin on your chest
- 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 medicines they recommend for you.
Complications of cardioversion
Cardioversion is usually a safe procedure, but sometimes it can cause complications.
- Cardioversion may cause other problems with your heart rhythm. You may need to take a medicine to treat this.
- You may get a blood clot. Having a blood clot after cardioversion can make you more likely to have a stroke. But your doctor will prescribe anticoagulant medicines before and after your procedure to reduce the chances of this happening.
Alternatives to cardioversion
This information 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 other treatments 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 must take these tablets long-term to help control your heart’s rate and rhythm. 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 stops any abnormal electrical signals.
- Pacemaker – if you have this device fitted, it can regulate your heartbeat if you have a slow heart rhythm. It’s often an option if medicines haven’t worked for you.
Speak to your doctor about whether any of these treatment options are right for you.
You may need anticoagulant medicines before cardioversion because they can reduce your risk of a blood clot. You’ll usually need to take them for at least three or four weeks before and after your cardioversion. If your cardioversion is urgent, you may be given an anticoagulant through a vein in your hand or arm first.
See the section on preparation for cardioversion above for more information.
You may need to take anti-arrhythmic medicines after cardioversion if it doesn’t work, or to stop your arrhythmia coming back after treatment. Anti-arrhythmic medicines help to regulate your heart rate and rhythm, and you may need to take them 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.
See the section on recovery following cardioversion above for more information.
It doesn’t take long to recover from cardioversion. You’ll usually feel back to normal after a few hours, once the anaesthetic or sedative has worn off. You can go home from hospital on the same day, although it’s possible you may need to stay overnight. Take it easy for a few days after your procedure. Your doctor will give you advice about what to do, including when you can return to work.
See the section on recovery following cardioversion above for more information.
You won’t be awake during cardioversion – you’ll have a sedative or a short-acting general anaesthetic first.
See the section on the cardioversion procedure above for more information.
You may feel tired or unsteady after cardioversion, and need to rest for a few hours until the anaesthetic or sedation has worn off. Ask family or a friend to drive you home and stay with you for the first 24 hours while you recover from the general anaesthetic or sedative.
See our section on aftercare following cardioversion for more information.
You can have cardioversion as many times as you need. There’s always a chance your heartbeat won’t be corrected by the shock and that your arrhythmia comes back again after a few days, weeks or months. If your arrhythmia comes back after cardioversion, your doctor may recommend you have the procedure again. But usually after two or three cardioversions, they’ll recommend you have a different treatment.
See our section on alternatives to cardioversion above for more information.
Echocardiogram
Electrocardiogram (ECG)
An electrocardiogram (ECG) is a test that can record the rhythm and electrical activity of your heart to find out if it’s healthy.
Ventricular tachycardia
Ventricular tachycardia is a type of abnormal heart rhythm (arrhythmia) in which your heart beats too fast.
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