What anticoagulation therapy should be initiated for a patient with atrial fibrillation (AF) lasting more than 24 hours?

Anticoagulation for AF >24 Hours Duration

For patients with atrial fibrillation lasting more than 24 hours who require cardioversion, you must provide therapeutic anticoagulation for at least 3 weeks before cardioversion and continue for at least 4 weeks afterward, using either a direct oral anticoagulant (DOAC) or warfarin (INR 2.0-3.0). 1

Pre-Cardioversion Anticoagulation Strategy

Standard Approach (AF >24 hours or unknown duration):

• Initiate therapeutic oral anticoagulation immediately 1
• DOACs are preferred over warfarin for thromboembolic risk reduction in eligible patients 1
• Wait minimum 3 weeks of therapeutic anticoagulation before scheduled cardioversion 1
  • For DOACs: Requires documented adherence to therapy 1
  • For warfarin: Requires INR ≥2.0 throughout this period 1

Alternative TEE-Guided Approach:

If 3 weeks of therapeutic anticoagulation has not been provided, you can perform transesophageal echocardiography (TEE) to exclude left atrial/appendage thrombus and enable early cardioversion 1

If no thrombus identified on TEE: 1

• Start therapeutic anticoagulation immediately (unfractionated heparin IV bolus followed by continuous infusion, or low-molecular-weight heparin) 1
• Proceed with cardioversion 1
• Continue oral anticoagulation (INR 2.0-3.0 or DOAC) for at least 4 weeks post-cardioversion 1

If thrombus identified on TEE: 1

• Continue oral anticoagulation (INR 2.0-3.0) for at least 3 weeks 1
• Postpone cardioversion 1
• Consider longer anticoagulation period as thromboembolic risk remains elevated 1

Post-Cardioversion Anticoagulation

All patients require therapeutic anticoagulation for minimum 4 weeks after cardioversion, regardless of baseline stroke risk or whether sinus rhythm is achieved 1

Long-term anticoagulation decisions should be based on thromboembolic risk factors (CHA₂DS₂-VASc score), not on successful cardioversion or maintenance of sinus rhythm 1

Critical Safety Point

Early cardioversion without appropriate anticoagulation or TEE is contraindicated if AF duration exceeds 24 hours 1. This restriction exists because atrial thrombi can form within 24-48 hours of AF onset, creating substantial stroke risk with cardioversion.

Choice of Anticoagulant

DOACs (apixaban, dabigatran, edoxaban, rivaroxaban) are recommended over warfarin in eligible patients 1, 2, 3, 4

Advantages of DOACs: 2, 3, 4

• Dramatic reduction in intracranial hemorrhage compared to warfarin 2
• Fixed dosing without routine monitoring 3
• No narrow therapeutic window concerns 2

Use warfarin (INR 2.0-3.0) when: 1, 5

• Mechanical heart valves present 1
• Moderate-to-severe mitral stenosis 1
• DOACs contraindicated or unavailable 5

Hemodynamically Unstable Exception

If hemodynamic instability present (shock, pulmonary edema, acute MI, symptomatic hypotension): 1

• Perform immediate electrical cardioversion without waiting for anticoagulation 1
• Start therapeutic-dose parenteral anticoagulation before cardioversion if possible, but do not delay emergency intervention 1
• After successful cardioversion, provide therapeutic anticoagulation for at least 4 weeks 1