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The Optimal Range of International Normalized Ratio for Radiofrequency Catheter Ablation of Atrial Fibrillation During Therapeutic Anticoagulation With Warfarin
Study Questions:
What is the relationship between international normalized ratio (INR) and the risk of thromboembolic and bleeding complications in patients undergoing radiofrequency catheter ablation (RFA) of atrial fibrillation (AF)?
Methods:
In this retrospective analysis, RFA was performed in 1,133 consecutive patients (mean age, 61 ± 10 years) with paroxysmal (550) or persistent AF (583). Patients were grouped based on the INR on the day of RFA. A multivariate logistic regression analysis was performed to determine the relationship between INR and complications. From the regression analysis, a quadratic model was developed and applied for the binary outcomes of bleeding complications.
Results:
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 2.1-2.5. 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 (ACT) during RFA was reduced by 50% in patients with an INR >2.0.
Conclusions:
The authors concluded that the optimal INR range during uninterrupted periprocedural anticoagulation using warfarin is narrow.
Perspective:
This study found that there is a quadratic relationship between the preprocedural INR and the risk of complications during RFA of AF. The risk of bleeding and thromboembolic complications is higher when the INR is subtherapeutic (<2), and the risk of bleeding complications is higher when the INR is >3, with a further steep increase in risk at INRs >3.5. Furthermore, clopidogrel use was an independent predictor of bleeding complications at all INRs. To minimize the risk of bleeding complications, it may be helpful to start monitoring INR earlier and more frequently before the procedure to achieve steady-state, stable INR values within the desired range. Additional studies are indicated to determine whether the use of new anticoagulants such as dabigatran or rivaroxaban will be safer than uninterrupted warfarin during RFA of AF.
Keywords: Odds Ratio, Multivariate Analysis, Morpholines, Pulmonary Veins, Warfarin, Heparin, Ticlopidine, International Normalized Ratio, Prevalence, Blood Coagulation, beta-Alanine, Benzimidazoles, Atrial Fibrillation, Confidence Intervals, Catheter Ablation, Hemorrhage, Logistic Models, Cardiac Tamponade
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