Atrial Fibrillation

• Issues in Management of AF

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• Should We Maintain Sinus Rhythm?
• The AFFIRM trial
• The SAFE-T trial- amiodarone vs sotalol vs placebo

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• Anticoagulation in AF
  • Risk of Thromboembolism-CHADS2
  • "Moderate Risk" Patients
  • "High-Risk" Patients
  • Secondary Prevention
  • Target INR level for AF patients
  • Maintain INR in theurapeutic range

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• Clopidogrel
  • Anticoagulation slightly better than Clopidogrel with Aspirin
  • Clopidogrel with Asprin better than Aspirin alone for those not eligible for anticoagulation

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• Cardioversion
• Role of Transoesophageal Echo in Cardioversion

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• Use of ACE-inhibitors or ARBs
• ACE-inhibitors may reduce the risk of recurrent PAF in those with lone PAF

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• Non-Pharmacological Therapy
• Options

Need To maintain INR in therapeutic range to benefit from oral anticoagulation

The INR should be within the therapeutic range at least 57% of the time to get benefit from oral anticoagulant therapy in chronic atrial fibrillation.

It has been demonstrated that subtherapeutic INR levels increase risk of stroke in patients with atrial fibrillation. In one study published in the New England Journal of Medicine in 1996 (Vol 335, pages 540-8), an INR of 1.7 doubled the risk of stroke.

An interesting analysis of the ACTIVE-W trial (Circulation 2008;118:2029-2037) found that patients got no benefit from Warfarin compared to Aspirin with Clopidogrel in centers where the time in therapeutic range was less than the median of 65%.

This post-hoc analysis of the ACTIVE-W trial found that oral anticoagulation reduced vascular events by more than two fold in centers where the time in therapeutic range was over the mean of 65%.

Statistical modeling led to the conclusion that time in therapeutic range had to be at least 58% to be confident that patients were obtaining benefit from oral anticoagulation therapy. Greater benefits can be expected if the INR is maintained in the therapeutic range for an even greater proportion of time.

Hitesh Patel
July, 2009.