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What is Cardioversion?

Cardioversion is defined as anything that converts the heart rhythm to normal. This sheet details elective electrical cardioversion. This is a procedure where a small electrical current is delivered to an abnormally beating heart to restore it to normal.

Why do I need cardioversion?

When the heart beats abnormally (known as arrhythmia or fibrillation) blood doesn’t get pumped effectively around the body. Because of this you may experience symptoms such as dizziness, shortness of breath, tiredness and palpitations (racing heart). Your doctor has most likely tried medications to correct this (chemical cardioversion) but they have not been successful and the symptoms may be affecting your day-to-day activity or heart function. With a successful cardioversion your heart rhythm will be restored to normal and you will feel much better.

What happens during cardioversion?

Prior to your cardioversion you will be given instructions on when to fast, what medications to take and to have a shower as normal. Do not apply lotions or powders to your skin and remove all your jewellery. When you arrive for your procedure the nursing staff will confirm that you have done all of this and that you have signed a consent form. You will be seen by an anaesthetist who will insert an IV line and you will be transferred to the theatre where the procedure will take place. You will be attached to a heart monitor and a light anaesthetic to make you sleepy will be delivered through the IV line. You will generally wake with no recollection of the procedure due to the effects of the sedation. For this reason you will need to be picked up by someone and you should not drive or make important decisions for the next 24 hours. Once you are asleep the staff will deliver a small electrical current to your chest via a defibrillator machine. This electrical current causes all the heart muscles to contract simultaneously, stopping all fibrillating contractions and allowing the heart’s natural pacemaker (the sinoatrial node) to take over and restore a normal heart beat. When you wake up you will have to stay to be observed. When you are stable you will be allowed to go home or back to the hospital ward.

What are the risks?

Because the upper chambers (atria) of the heart are fibrillating (quivering) and do not contract effectively there is a risk of blood clots forming. Restoring the heart rhythm with cardioversion can cause these blood clots to dislodge when the heart begins contracting normally, causing a heart attack or stroke. This risk can be minimised by thinning the blood prior to the procedure. This thinning is known as anticoagulation. Drugs such as Warfarin or Heparin/Clexane or aspirin/plavix are usually prescribed for around three to four weeks prior to cardioversion. Blood tests are taken to ensure the blood is thin enough. A transoesophageal echocardiogram (TOE) may be performed prior to cardioversion. An information sheet on this procedure will also be given to you. Sometimes some skin irritation can occur on your chest from the defibrillator pads, but a mild soothing cream will ease this.


A normal heart rhythm is restored in most cases. Some people may experience an abnormal rhythm later on and cardioversion may need to be repeated. If you start to feel any of the symptoms you had previously or are concerned in any way, please contact your doctor to make another appointment.