title: How does warfarin affect the activated coagulation time?
abstract: BACKGROUND
  The activated coagulation time (ACT) is a rapid measurement of a patient's level of heparin anticoagulation during cardiac catheterization. Patients receiving warfarin therapy occasionally are seen at the catheterization laboratory for emergent procedures. The effects of warfarin on ACT activity have not been previously described. We compared the ACT and the international normalized ratios (INR) in 77 patients receiving warfarin and 57 patients who were not receiving any anticoagulation (controls).
  
  
  RESULTS
  Both the mean ACT (131+/-17.0 seconds) and INR (2.5+/-0.90 seconds) of the anticoagulated patients differed from the controls (ACT=115+/-14.5 seconds, INR=1.0+/-0.10 seconds; P< 0.05). The ACT increased linearly with INR in the warfarin group (r=0.70, P< .001). There was no relation between ACT and INR in the control group.
  
  
  CONCLUSIONS
  Patients receiving warfarin therapy will have a linear increase in ACT develop similar to patients receiving heparin therapy.
authors.affiliation: Department of Medicine, Harbor-UCLA Medical Center, Torrance, Calif 90509, USA. DrRChang@POL.NET
authors.forename: R J
authors.initials: RJ
authors.lastname: Chang
authors.forename: T M
authors.initials: TM
authors.lastname: Doherty
authors.forename: S L
authors.initials: SL
authors.lastname: Goldberg
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000494:pharmacology*; D001777:Blood Coagulation / Q000187:drug effects*; D006328:Cardiac Catheterization; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D014859:Warfarin / Q000494:pharmacology*; D014914:Whole Blood Coagulation Time
chemical_list: D000925:Anticoagulants; D014859:Warfarin