IIa B For patients with AF or atrial flutter of 48 hours duration or longer or of unknown duration who have not been anticoagulated for the preceding 3 weeks, it is reasonable to perform transesophageal echocardiography before cardioversion and proceed with cardioversion if no left atrial thrombus is identified, including in the LAA, provided that anticoagulation is achieved before transesophageal echocardiography and maintained after cardioversion for at least 4 IIb B-NR For patients with AF or atrial flutter of less than 48 hours duration with a CHA2 - VASc score of 0 in men or 1 in women, administration of heparin, a factor Xa inhibitor, or a direct thrombin inhibitor, versus no anticoagulant therapy, may be considered before cardioversion, without the need for postcardioversion oral MODIFIED: Recommendation LOE was changed from C in the 2014 AF Guideline to B-NR to reflect evidence from 2 registry studies and to include specific CHA2 -VASc scores derived from study results. Recommendation-Specific Supportive Text (New or Modified) 1. Three prospective RCTs have evaluated the safety and efficacy of newly initiated factor Xa inhibi- tors (rivaroxaban and apixaban) for cardioversion as an alternative to warfarin.S6.1.1-7,S6.1.1-8,S6.1.1-17 In addition, retrospective analyses have been per- formed on the subset of patients undergoing cardioversion within the context of the larger randomized trials that compared each of the FDA-approved NOACs with warfarin for throm- boembolism prevention with AF. The results were consistent and support the assertion that NOACs are an effective and safe alternative to warfarin for patients undergoing cardioversion. An alter- native to waiting 3 weeks before cardioversion is to perform transesophageal echocardiography to exclude thrombus (see separate recommen- dation in this section). The decision about long- term anticoagulant therapy (beyond 4 weeks) is based on the thromboembolic risk profile (Section 4) and bleeding risk profile. 