A cardioversion is a treatment which delivers an electrical energy (shock) to the heart using an external defibrillator to get the heart back into sinus rhythm. This is done by attaching electrodes (sticky pads) to the chest to deliver the electric shock.

Cardioversion is very quick and can be very effective in many patients. In some patients, sinus rhythm can be maintained for several years and in others it can be much shorter. The length of time your sinus rhythm is maintained will depend on how long you have been in atrial fibrillation (AF) and other factors, such as how large your left atrium is.

Cardioversion and anticoagulants

Once you have your referral for cardioversion, you need to make sure that you have been taking your anticoagulant (such as warfarin or a direct oral anticoagulant) for at least 3-4 weeks before the procedure.

Warfarin

If you are taking warfarin, you will need to have weekly INR levels between two and three for at least four consecutive weeks leading up to the planned cardioversion. If the levels fall below two before your cardioversion, we will need to delay your procedure. This is because your risk of stroke increases.

If the levels have fallen below 2 prior to your cardioversion, you are at risk of a stroke and your procedure will need to be delayed. After the cardioversion you will need to continue your warfarin for at least four weeks, or indefinitely if you have a CHA2DS2VASc score ≥ 1. This will be reviewed at your next clinic appointment.

Direct oral anticoagulants

If you are taking one of the direct oral anticoagulants (dabigatran, rivaroxaban, apixaban or edoxaban) then you will need to take these as instructed for at least 3 to 4 weeks before the cardioversion. It is very important that you do not miss any doses of your anticoagulant as your risk of stroke will be increased and your procedure will need to be delayed.

Before the procedure

You will have a telephone pre-admission appointment prior to your cardioversion. This appointment is a nurse-led clinic run by the arrhythmia nurse specialists, who will take a full medical history, including your INR levels (if you are taking warfarin) and your current medication list. The procedure will be explained to you during this appointment and you will also be told if there is any medication that you should not take before the procedure.

The procedure

You will be admitted to the day care unit or cardiology ward on the morning of your cardioversion. A doctor or clinical nurse specialist will examine you to ensure you are fit for the procedure. An ECG (electrocardiogram) will be taken to confirm that the arrhythmia is still present. The procedure will be explained to you again and you will be asked to sign a consent form.

Once we have confirmed that you are ready for the procedure, you will be taken to another department. You will be met by the anaesthetist and a doctor or nurse who will explain what they are going to do.

Two electrode patches will be placed on the upper right and lower left side of the chest and this will be attached to the defibrillator. A cannula (small needle) will be put in the back of your hand or in your arm. You will be given a short general anaesthetic to put you to sleep. The defibrillator is then charged and ready to deliver a shock. One shock can be sufficient to restore sinus rhythm. However, a small number of people may require further shocks, and a small percentage of patients will remain in AF despite several attempts.

Like any intervention there are possible risks. These include:

  • Stroke - this is rare if the INR levels have been within the therapeutic range of 2-3 / or you have been taking your DOAC for at least three consecutive weeks.
  • Bradycardia - this is normally very brief following the cardioversion. A small percentage of patients may require intravenous medication or external pacing of the heart via the two electrodes that delivered the shock. In very rare cases, a permanent pacemaker may be required.
  • Ventricular tachycardia - this is rare but can occur following the initial shock and would require a further shock to establish sinus rhythm.
  • Skin burns from the electrode pads - this is rare but should this occur you will be given a cream to apply to the affected areas.

After the procedure

We will admit you to the day case unit/cardiology ward the morning of your cardioversion. You will then meet one of our doctors or clinical nurse specialists. They will take a full medical history, do blood tests including checking your INR levels and make sure that you are fit for the procedure.

We will do an ECG (electrocardiogram) to confirm that the arrhythmia is still present. We will then explain the procedure and ask you to sign a consent form. 

Once we have confirmed that you are ready for the procedure, we will take you to another department. You will meet the anaesthetist and a doctor/nurse who will explain what they are going to do. 

We will place two electrode patches on the upper right and lower left of your chest. These are then attached to the defibrillator. A cannula (small needle) is put into the back of your hand or in your arm. The anaesthetist will give you a short general anaesthetic to put you to sleep.

The defibrillator is then charged and ready to deliver a shock. One shock can be enough to restore sinus rhythm. But for a small number of people, they will need more shocks. Also for a small percentage of patients, they will remain in AF even after several attempts.  

Like any intervention, there are possible risks. These include:

  • Stroke - this is rare if INR levels have been within the therapeutic range of two to three for at least three consecutive weeks

  • Bradycardia - this is normally very brief following the cardioversion. A small percentage of patients may need intravenous medication or external pacing of the heart via the two electrodes that delivered the shock. In very rare cases, the patient may need to have a permanent pacemaker.

  • Ventricular tachycardia - this is rare but can occur following the initial shock. You would need a further shock to establish sinus rhythm.

  • Skin burns from the electrode pads - if this occurs, we will give you a cream to apply to the affected areas

After the procedure

After your procedure, we will take you back to the day-case unit/ward to recover.

You will be monitored for up to 4 hours before being allowed to go home. An ECG will be taken prior to discharge to ensure you have remained in sinus rhythm.

You will need someone to collect you, as you are not allowed to drive for 24 hours following this procedure.

You will be seen in clinic by either your doctor or clinical nurse specialist approximately 2 -3 months following your cardioversion. If your discharge ECG shows AF, you will be booked back into clinic earlier to discuss further treatment options.

Atrial tachycardia is an abnormal heart rhythm which is usually seen in patients that have undergone heart surgery, have congenital heart defects or have undergone previous ablation procedures.

Atrial fibrillation is an an irregular heart rhythm, which starts in the upper chambers (atria) of the heart. 

Contact our atrial fibrillation team

Harefield Hospital

01895 828979

Royal Brompton Hospital

020 7351 8364 


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