We recommend that <i>hemodynamically stable</i> patients with AF or AFL of &ge;<i>48 hours or uncertain duration</i> for whom electrical or pharmacologic cardioversion is planned should receive therapeutic OAC therapy (warfarin [INR 2-3] or dabigatran) for 3 weeks before and at least 4 weeks post-cardioversion.<br /><br />Following attempted cardioversion,<br /><ul><li>If AF or AFL persists or recurs or if symptoms suggest that the presenting AF or AFL has been recurrent, the patient should have antithrombotic therapy continued indefinitely (using either OAC or aspirin, as appropriate).</li><li>If sinus rhythm is achieved and sustained for 4 weeks, the need for ongoing antithrombotic therapy should be determined on the basis of the risk of stroke, and in selected cases expert consultation may be required. (Recommendation Strong, Quality Moderate)</li></ul><br /><br />We recommend that hemodynamically stable patients with AF or AFL of known duration less than 48 hours may undergo cardioversion without prior or subsequent anticoagulation. However, if the patient is at particularly high risk of stroke (eg, mechanical valve, rheumatic heart disease, recent stroke, or TIA), cardioversion should be delayed, and the patient should receive OAC for 3 weeks before and at least 4 weeks post-cardioversion.<br /><br />Following attempted cardioversion,<br /><li>If AF or AFL persists or recurs or if symptoms suggest that the presenting AF or AFL has been recurrent, antithrombotic therapy (OAC or aspirin, as appropriate) should be commenced and continued indefinitely.</li><li>If normal sinus rhythm is achieved and sustained for 4 weeks, the need for ongoing antithrombotic therapy should be determined on the basis of the risk of stroke according to CHADS<sub>2</sub> score, and in selected cases expert consultation may be required.  (Recommendation Strong, Quality Moderate)</li></ul><br /><br />We suggest that hemodynamically unstable patients with AF or AFL who require emergency cardioversion be managed as follows:<br /><ul><li>If the AF or AFL is of known duration less than 48 hours, the patient may generally undergo cardioversion without prior anticoagulation. However, if the patient is at particularly high risk of stroke (eg, mechanical valve, rheumatic heart disease, recent stroke, or TIA), the patient should receive IV UFH or LMWH before cardioversion if possible, or immediately thereafter if even a brief delay is unacceptable, and then be converted to OAC for at least 4 weeks post-cardioversion.</li><li>If the AF or AFL is of &ge;48 hours or of uncertain duration, we suggest the patient receive intravenous UFH or LMWH before cardioversion if possible, or immediately thereafter if even a brief delay is unacceptable. Such a patient should then be converted to OAC for at least 4 weeks post-cardioversion.</li></ul><br /><br />Following attempted cardioversion, the guidelines for subsequent antithrombotic therapy are identical to those for the management of hemodynamically stable patients undergoing cardioversion.  (Recommendation Conditional, Quality Low)