There are two scenarios where cardioversion may be used in atrial fibrillation:

• electrical cardioversion as an emergency if the patient is haemodynamically unstable
• electrical or pharmacological cardioversion as an elective procedure where a rhythm control strategy is preferred.

Electrical cardioversion is synchronised to the R wave to prevent delivery of a shock during the vulnerable period of cardiac repolarisation when ventricular fibrillation can be induced.

Onset <48 hours

If the atrial fibrillation (AF) is definitely of less than 48 hours onset patients should be heparinised. Patients who have risk factors for ischaemic stroke should be put on lifelong oral anticoagulation. Otherwise, patients may be cardioverted using either:

• electrical - 'DC cardioversion'
• pharmacology - amiodarone if structural heart disease, flecainide or amiodarone in those without structural heart disease

Following electrical cardioversion if AF is confirmed as being less than 48 hours duration then further anticoagulation is unnecessary

Onset >48 hours

If the patient has been in AF for more than 48 hours then anticoagulation should be given for at least 3 weeks prior to cardioversion. An alternative strategy is to perform a transoesophageal echo (TOE) to exclude a left atrial appendage (LAA) thrombus. If excluded patients may be heparinised and cardioverted immediately.

NICE recommend electrical cardioversion in this scenario, rather than pharmacological.

If there is a high risk of cardioversion failure (e.g. Previous failure or AF recurrence) then it is recommend to have at least 4 weeks amiodarone or sotalol prior to electrical cardioversion

Following electrical cardioversion patients should be anticoagulated for at least 4 weeks. After this time decisions about anticoagulation should be taken on an individual basis depending on the risk of recurrence