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J Cardiovasc Electrophysiol. 2011 Mar;22(3):248-54. doi: 10.1111/j.1540-8167.2010.01894.x. Epub 2010 Aug 31.

Effect of therapeutic INR on activated clotting times, heparin dosage, and bleeding risk during ablation of atrial fibrillation.

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Division of Cardiovascular Medicine, Brigham and Women's Hospital, 45 Francis St., Boston, MA 02115, USA.



Ablation of atrial fibrillation (AF) with international normalized ratio (INR) ≥ 2.0 is safe and may reduce thromboembolic complications. Heparin is administered during the procedure, but the effect of elevated INR on heparin requirements and target activation clotting times (ACT) ≥ 350 seconds during ablation is unknown.


To study the effect of INR on intraprocedural anticoagulation during ablation of AF.


We retrospectively studied 427 consecutive patients over an 18-month period when we were transitioning to continuation of warfarin for AF ablation. Baseline INR, procedural ACT measurements, heparin doses and major complications were analyzed according to Group 1 with INR < 2.0 (n = 246) and Group 2 with INR ≥ 2.0 (n = 181).


In Group 1, the mean INR was lower (1.3 ± 0.3 s vs 2.4 ± 0.3; P < 0.001), and the mean heparin dose was greater (106.82 ± 40.01 vs 77.03 ± 18.5 U/kg; P < 0.001). A single heparin bolus achieved ACT ≥ 350 seconds throughout the procedure in 51 patients (20.7%) in Group 1 compared to 108 patients (59.7%) in Group 2 (P < 0.01). Mean ACT values were higher in Group 2. Symptomatic pericardial effusions were similar (2.4% in Group 1 and 2.2% in Group 2). There were 3 thromboembolic cerebrovascular events in Group 1 and none in Group 2. Femoral hematomas occurred more frequently in Group 1 (8.1%) than in Group 2 (3.3%) (P = 0.007).


AF ablation with INR ≥ 2.0 provides a consistent anticoagulant milieu during the procedure, with lower heparin requirements that are important to anticipate.

[Indexed for MEDLINE]

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