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The Optimal Range of International Normalized Ratio for Radiofrequency Catheter Ablation of Atrial Fibrillation During Therapeutic Anticoagulation With Warfarin

Background—Uninterrupted anticoagulation with warfarin during radiofrequency catheter ablation (RFA) of atrial fibrillation is associated with a lower risk of periprocedural complications than when warfarin is temporarily discontinued. However, the optimal international normalized ratio (INR) levels during RFA have not been defined. Methods and Results—In this retrospective analysis, RFA was performed in 1133 consecutive patients (mean age, 61±10 years) with paroxysmal (550) or persistent atrial fibrillation (583). Patients were grouped based on the INR on the day of RFA. There was a quadratic relationship between the INR and bleeding and vascular complications (P<0.001). Complications were less prevalent when INR was ≥2.0 and ⩽3.0 (5% [31/572]) than when INR was <2.0 (10% [49/485]; P=0.004) and >3.0 (12% [9/76]; P=0.03). The prevalence of pericardial tamponade (1%) was similar at all INRs. From the quadratic model, the optimal range of INR was calculated as 2.1 to 2.5. INRs<2.0 and >3.0 were associated with a >2-fold increase in complications, with a further steep rise beyond an INR>3.5. Concomitant clopidogrel use was associated with a significant increase in complications at all INRs (odds ratio=3.1; ±95% confidence interval, 1.4–7.4). Unfractionated heparin requirements to maintain a therapeutic activated clotting time during RFA was reduced by 50% in patients with an INR>2.0. Conclusions—The optimal INR range during uninterrupted periprocedural anticoagulation using warfarin is narrow. Therefore, INR levels should be carefully monitored in preparation for RFA of atrial fibrillation.