In an elderly patient with atrial fibrillation and prior stroke who was on warfarin (Coumadin) 5 mg daily, held doses and now has a therapeutic International Normalized Ratio of 2.9, how should anticoagulation be managed?

Warfarin Management for Elderly Patient with AF and Prior Stroke

Resume warfarin at a reduced maintenance dose of 2.5 mg daily and recheck INR in 3-5 days, as the current INR of 2.9 is within the therapeutic target range of 2.0-3.0 recommended for secondary stroke prevention in atrial fibrillation. 1

Rationale for Resuming Anticoagulation

This elderly patient with atrial fibrillation and prior stroke is at extremely high risk for recurrent stroke—approximately 10.8 strokes per 100 patient-years without anticoagulation. 2 Patients with prior stroke or TIA in the setting of atrial fibrillation should be considered at high risk for recurrence and must be treated with warfarin unless contraindicated. 2

The current INR of 2.9 falls within the recommended therapeutic range:

• The target INR for secondary stroke prevention is 2.5 (range 2.0-3.0) for most patients with atrial fibrillation and prior stroke. 2, 1
• Some experts recommend a target INR of 2.0 (range 1.6-2.5) for primary prevention in patients over 75 years to minimize bleeding risk, but this patient requires secondary prevention given the stroke history. 2, 3
• Age alone is not a contraindication to standard-intensity anticoagulation in high-risk atrial fibrillation patients, as the stroke prevention benefit exceeds bleeding risk in the vast majority of cases. 2, 3

Specific Dosing Recommendation

Restart warfarin at 2.5 mg daily based on the following logic:

• The patient was previously stable on 5 mg daily, which produced an INR of 3.4 (slightly supratherapeutic). 1
• After dose reduction to 2.5 mg for one day followed by a 2-day hold, the INR is now 2.9 (therapeutic). 1
• This suggests the patient's maintenance dose is likely between 2.5-3.75 mg daily. 1
• Starting at 2.5 mg daily is conservative and allows for upward titration if needed. 1

Monitoring Plan

Recheck INR in 3-5 days after resuming warfarin to ensure the patient remains in therapeutic range. 1 Once stable:

• Continue weekly INR monitoring until three consecutive values remain between 2.0-3.0. 1
• After achieving stability, transition to monthly INR monitoring. 1
• Aim for time in therapeutic range (TTR) ≥65-70% to maximize efficacy and safety. 1

Critical Pitfalls to Avoid

Do not leave this patient off anticoagulation. The annual stroke risk without anticoagulation is approximately 10.8% per year for patients with AF and prior stroke, which translates to a 5-day risk that far exceeds any bleeding concerns. 2, 4

Do not target a lower INR range (1.6-2.5) in this patient. Lower INR targets provide only approximately 80% of the stroke protection achieved with standard-intensity anticoagulation (INR 2.0-3.0), which is unacceptable for secondary prevention. 2

Do not add aspirin to warfarin therapy unless there is a compelling cardiovascular indication, as combination therapy increases bleeding risk without additional stroke benefit in atrial fibrillation. 3

Additional Management Considerations

• Ensure blood pressure is well-controlled to reduce both ischemic stroke risk and intracranial hemorrhage risk during anticoagulation. 3
• Assess renal function at least annually, as renal impairment increases bleeding risk. 3
• Review all medications to avoid concomitant NSAIDs or unnecessary antiplatelet agents that increase bleeding risk. 2, 3
• Implement fall prevention strategies rather than withholding anticoagulation, as a patient would need to fall 295 times per year before the risk of subdural hemorrhage outweighs the stroke prevention benefit. 3