Atrial fibrillation lasting longer than 48 hours and patient is haemodynamically stable

Haemodynamically stable patients with atrial fibrillation lasting longer than 48 hours have an increased risk of developing a left atrial thrombus; consider the thromboembolic risk before cardioverting with either a drug or direct current (DC) electrical cardioversion.

If atrial fibrillation has lasted longer than 48 hours, or if the duration of atrial fibrillation is unknown, do not perform acute cardioversion unless left atrial thrombus has been excluded, or the patient has had therapeutic anticoagulation for a minimum of 3 weeksNational Institute for Health and Care Excellence (NICE), 2021. If atrial thrombus has not been excluded, or the patient is not anticoagulated, rate control is the preferred initial treatment (see Rate control for atrial fibrillation).

For patients who are not anticoagulated, transoesophageal echocardiography (TOE) may be considered to exclude left atrial thrombus and allow for early cardioversion. For these patients, anticoagulant therapy should be started at the time of cardioversion and continued for a minimum of 4 weeks after cardioversionJanuary, 2019.

See Acute rhythm control for atrial fibrillation for information about cardioversion.