title: Impact of international normalized ratio and activated clotting time on unfractionated heparin dosing during ablation of atrial fibrillation.
abstract: BACKGROUND
  For ablation of atrial fibrillation, it is unclear how baseline international normalized ratio (INR) affects the dosing of unfractionated heparin (UFH).
  
  
  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). The amount of UFH to achieve the first ACT ≥300 seconds was significantly higher for G<2 versus G≥2 (9701±2390 versus 8268±2366 U; P=0.0001). Baseline INR, ACT, and weight were predictors of the UFH dosage to achieve an ACT ≥300 seconds. An equation derived to achieve an ACT ≥300 seconds after a single bolus of UFH met this end point in 160 of 168 patients (95%).
  
  
  CONCLUSIONS
  Baseline INR and ACT, in addition to weight, are the only predictors of UFH dosage needed to achieve an ACT ≥300 seconds. A derived equation predicted the UFH dosage to achieve an ACT ≥300 seconds.
authors.affiliation: Division of Cardiology, Ohio State University Wexner Medical Center, Ohio State University, Columbus, OH 43210, USA. Ismail.hamam@osumc.edu
authors.forename: Ismail
authors.initials: I
authors.lastname: Hamam
authors.forename: Emile G
authors.initials: EG
authors.lastname: Daoud
authors.forename: Jianying
authors.initials: J
authors.lastname: Zhang
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Kalbfleisch
authors.forename: Ralph
authors.initials: R
authors.lastname: Augostini
authors.forename: Marshall
authors.initials: M
authors.lastname: Winner
authors.forename: Shane
authors.initials: S
authors.lastname: Tsai
authors.forename: Troy E
authors.initials: TE
authors.lastname: Rhodes
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Houmsse
authors.forename: Zhenguo
authors.initials: Z
authors.lastname: Liu
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Love
authors.forename: Jaret
authors.initials: J
authors.lastname: Tyler
authors.forename: Molly
authors.initials: M
authors.lastname: Sachdev
authors.forename: Raul
authors.initials: R
authors.lastname: Weiss
authors.forename: John D
authors.initials: JD
authors.lastname: Hummel
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000188:drug therapy* / Q000601:surgery*; D001777:Blood Coagulation / Q000187:drug effects*; D017115:Catheter Ablation / Q000009:adverse effects / Q000379:methods*; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006493:Heparin / Q000008:administration & dosage*; D006801:Humans; D019934:International Normalized Ratio; D007430:Intraoperative Care / Q000379:methods; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012044:Regression Analysis; D012189:Retrospective Studies; D018570:Risk Assessment; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D006493:Heparin
keywords: anticoagulants; atrial fibrillation; catheter ablation; heparin; warfarin