Impact of International Normalized Ratio and Activated Clotting Time on Unfractionated Heparin Dosing During Ablation of Atrial Fibrillation

Background—For ablation of atrial fibrillation, it is unclear how baseline international normalized ratio (INR) affects the dosing of unfractionated heparin (UFH).

Methods and Results—A retrospective review of 170 consecutive patients undergoing atrial fibrillation ablation with baseline activated clotting time (ACT) and INR values was performed. Patients were grouped according to INR <2.0 (G<2; n=129) and INR ≥2.0 (G≥2; n=41). Clinical variables, UFH doses, and ACT values were recorded. An equation was derived to calculate the first bolus of UFH required to achieve an ACT ≥300 seconds, and this was subsequently assessed in 168 patients. For the initial 170 patients, the baseline INR (2.47±0.31 versus 1.53±0.31) and ACT (185±26 versus 153±30 seconds) were significantly greater in G≥2 (P<0.001).   Read more