title: Tissue factor pathway inhibitor antigen and activity in 96 patients receiving heparin for cardiopulmonary bypass.
abstract: OBJECTIVE
  To identify patients with poor tissue factor pathway inhibitor (TFPI) response to heparin and observe any association with increased risk of excessive coagulation activation, morbidity, or mortality.
  
  
  METHODS
  Prospective, observational cohort study.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  Patients (n = 96) undergoing cardiopulmonary bypass for various types of surgery.
  
  
  METHODS
  None.
  
  
  RESULTS
  TFPI antigen and activity were determined in patients before and after heparin administration, before cardiopulmonary bypass for cardiac surgery. The clinical progress of each patient was recorded. Median levels of TFPI activity were 0.98 U/mL (interquartile range, 0.83 to 1.14 U/mL) preheparin and 2.34 U/mL (2.18 to 2.54 U/mL) postheparin (p < 0.0001), representing a median 2.3-(2.1- to 2.8-) fold increase. Median TFPI antigen levels were 92.4 ng/mL (73.0 to 119.5 ng/mL) preheparin and 422.9 ng/mL (398.7 to 501.6 ng/mL) postheparin (p < 0.0001), representing a median 4.6-fold (3.6- to 6.2-fold) increase. Two patients had low (<300 ng/mL) postheparin levels of TFPI antigen that were not associated with low functional TFPI or adverse clinical outcome. Fourteen patients showed a low ratio of increased functional TFPI postheparin; all had a ratio of TFPI antigen increase of at least 3-fold.
  
  
  CONCLUSIONS
  The TFPI response to heparin is heterogenous. Two nonresponders were identified, with low postheparin levels of TFPI antigen, who did not suffer adverse clinical outcomes.
authors.affiliation: Haematology Department, and Centre for Anaesthesia, University College London, London. United Kingdom.
authors.forename: Murray J
authors.initials: MJ
authors.lastname: Adams
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Cardigan
authors.forename: Warwick A
authors.initials: WA
authors.lastname: Marchant
authors.forename: Michael P W
authors.initials: MP
authors.lastname: Grocott
authors.forename: Monty G
authors.initials: MG
authors.lastname: Mythen
authors.forename: Maj
authors.initials: M
authors.lastname: Mutch
authors.forename: Gordon
authors.initials: G
authors.lastname: Purdy
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Mackie
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Machin
mesh_terms: D000293:Adolescent; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000097:blood / Q000627:therapeutic use*; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass; D015331:Cohort Studies; D065427:Factor Xa Inhibitors; D005260:Female; D006493:Heparin / Q000097:blood / Q000627:therapeutic use*; D006801:Humans; D008074:Lipoproteins / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies
chemical_list: D000925:Anticoagulants; D065427:Factor Xa Inhibitors; D008074:Lipoproteins; C051928:lipoprotein-associated coagulation inhibitor; D006493:Heparin