What is the most appropriate anticoagulation regimen to decrease thromboembolism risk in a 60-year-old male with paroxysmal atrial fibrillation (AF), normal renal function, and a history of transient ischemic attacks (TIAs) and diabetes?

Anticoagulation for Thromboembolism Prevention in Paroxysmal Atrial Fibrillation

Rivaroxaban 20 mg daily is the most appropriate regimen to decrease KL's thromboembolism risk based on his history of TIAs, diabetes, and normal renal function. 1

Risk Assessment

KL's thromboembolism risk factors include:

• Age 60 years
• History of transient ischemic attacks (TIAs)
• Diabetes mellitus
• Paroxysmal atrial fibrillation

Using the CHA₂DS₂-VASc score:

• Diabetes: +1 point
• Prior TIA: +2 points
• Total score: 3 points

With a CHA₂DS₂-VASc score of 3, KL has a high risk of stroke and requires anticoagulation therapy 2, 1.

Anticoagulation Selection Algorithm

1. Determine need for anticoagulation:

   • CHA₂DS₂-VASc score ≥2 in males indicates need for oral anticoagulation 1
   • KL's score is 3, indicating definite need for anticoagulation

2. Assess renal function:

   • KL's serum creatinine is 0.9 mg/dL
   • Calculated creatinine clearance (using Cockcroft-Gault):
     • CrCl = [(140-60) × 88] ÷ [72 × 0.9] = 113 mL/min
   • Normal renal function supports standard DOAC dosing 1

3. Select appropriate anticoagulant:

   • Direct oral anticoagulants (DOACs) are preferred over warfarin for non-valvular AF 1
   • KL has no contraindications to DOACs (no mechanical valve, no severe renal impairment)

Rationale for Rivaroxaban 20 mg Daily

Rivaroxaban 20 mg daily is appropriate for KL because:

1. He has normal renal function (CrCl >50 mL/min), supporting the standard 20 mg once-daily dose 1, 3

2. His history of TIAs makes him high-risk for stroke, requiring full anticoagulation 2

3. Once-daily dosing may improve adherence compared to twice-daily regimens 4

4. Rivaroxaban has been shown to be non-inferior to warfarin for stroke prevention in AF patients 3

Why Not the Other Options?

• Apixaban 2.5 mg BID: This is a reduced dose typically reserved for patients meeting at least 2 of the following criteria: age ≥80 years, weight ≤60 kg, or serum creatinine ≥1.5 mg/dL 5. KL meets none of these criteria and should receive the standard dose of 5 mg BID if apixaban were chosen.

• Dabigatran 75 mg BID: This dose is too low for KL. The standard dose for AF with normal renal function is 150 mg BID 6.

• Edoxaban 60 mg daily: While this would be an appropriate dose for KL, some evidence suggests slightly lower efficacy compared to dabigatran for stroke prevention 7.

Monitoring and Follow-up Considerations

1. Assess for bleeding risk using the HAS-BLED score 1

2. No routine coagulation monitoring is required with rivaroxaban 4

3. Renal function should be monitored periodically, especially if there are changes in health status 1

4. Educate KL that rivaroxaban must be taken with food to ensure adequate absorption 1

5. Advise KL about bleeding risk and signs/symptoms that warrant medical attention

Important Cautions

• If KL develops significant renal impairment (CrCl 15-50 mL/min), dose reduction to rivaroxaban 15 mg daily would be necessary 3

• Unlike warfarin, rivaroxaban has a more rapid onset and offset of action, making adherence particularly important 4

• If KL requires procedures in the future, specific management of his anticoagulation will be needed based on bleeding risk of the procedure 2