title: Response to aspirin and clopidogrel in patients scheduled to undergo cardiovascular surgery.
abstract: BACKGROUND
  Recent data indicate that among patients undergoing percutaneous coronary intervention low platelet response to aspirin is associated with clopidogrel low response. It is unclear whether these findings extend to other patient populations. We, therefore, aimed to evaluate the relation between response to aspirin and clopidogrel among patients scheduled to undergo cardiac or vascular surgery.
  
  
  METHODS
  Patients who were scheduled for cardiac or vascular surgery and had taken aspirin 81-325 mg daily for at least a week and clopidogrel 75 mg daily for at least 3 days underwent blood testing for platelet function. One hundred patients were included in the current analysis. Platelet function was evaluated by the modified TEG platelet mapping assay with addition of ADP or arachidonic acid (AA), and by the PFA-100 assay with collagen-epinephrine (CEPI) or collagen-ADP (CADP) cartridges. Low response to aspirin or clopidogrel was defined as inhibition < or =20% for TEG-AA or TEG-ADP, respectively.
  
  
  RESULTS
  Thirteen patients (13%) were low responders to aspirin and 34 (34%) were low responders to clopidogrel. Eight patients were low responders to both drugs. There were no differences in clinical characteristics between drug low responders versus sensitive patients. Aspirin low responders had lower TEG-ADP inhibition (19.5 +/- 6 vs. 35.8 +/- 3%, P = 0.03) and tended to have lower PFA-CADP time (84.7 +/- 7 vs. 105.6 +/- 5 s, P = 0.1) than aspirin sensitive patients. Clopidogrel low responders had lower TEG-AA inhibition (58 +/- 6 vs. 75.1 +/- 4%, P = 0.01) and PFA-CEPI time (168 +/- 13 vs. 200.4 +/- 10 s, P = 0.07) than clopidogrel sensitive patients.
  
  
  CONCLUSIONS
  In patients scheduled to undergo cardiovascular surgery low response to aspirin is associated with low response to clopidogrel.
authors.affiliation: Department of Cardiology, The Methodist Hospital Research Institute, The Methodist DeBakey Heart Center, Houston, TX 77030, USA.
authors.forename: Eli I
authors.initials: EI
authors.lastname: Lev
authors.forename: Mahesh
authors.initials: M
authors.lastname: Ramchandani
authors.forename: Rajeev
authors.initials: R
authors.lastname: Garg
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Wojciechowski
authors.forename: Angela
authors.initials: A
authors.lastname: Builes
authors.forename: Muthiah
authors.initials: M
authors.lastname: Vaduganathan
authors.forename: Uttam
authors.initials: U
authors.lastname: Tripathy
authors.forename: Neal S
authors.initials: NS
authors.lastname: Kleiman
mesh_terms: D000368:Aged; D001241:Aspirin / Q000097:blood / Q000627:therapeutic use*; D002318:Cardiovascular Diseases / Q000601:surgery*; D000077144:Clopidogrel; D001026:Coronary Artery Bypass; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000097:blood / Q000627:therapeutic use*; D010976:Platelet Count; D011300:Preoperative Care; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000097:blood / Q000627:therapeutic use; D016896:Treatment Outcome
chemical_list: D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin