title: Aspirin resistance in off-pump coronary artery bypass grafting.
abstract: OBJECTIVE
  Anti-platelet therapy with aspirin is the cornerstone of treatment after coronary artery bypass grafting (CABG). Aspirin resistance describes the clinical observation of the inability of aspirin to prevent thrombotic complications or the laboratory phenomenon of absence of the effect of aspirin on platelet inhibition tests. Off-pump CABG (OPCAB) is associated with reduced platelet activation and turnover compared to on-pump surgery which may indicate that aspirin is more effective after OPCAB. Our aim was to evaluate the efficacy of aspirin and incidence of aspirin resistance in patients undergoing OPCAB.
  
  
  METHODS
  A total of 331 patients was recruited, of which 111 underwent primary OPCAB (group A) and 220 controls with ischaemic heart disease received medical therapy. Arachidonic acid-induced platelet aggregation and urinary 11-dehydro thromboxane B2 (11-dehydroTxB2) were measured at baseline and following aspirin administration on days 1, 4 and 10. A 6-month follow-up was completed in patients who developed aspirin resistance.
  
  
  RESULTS
  On the first postoperative day, 78 patients (70.3%) were aspirin sensitive (AS) and 33 (29.7%) were aspirin resistant (AR). Of the latter, 18 (16.2%) and five (4.5%) patients remained resistant on days 4 and 10, respectively. AR patients had significantly greater platelet aggregation and urinary 11-dehydroTxB2 levels at all time points than those in the AS group. All patients in the AR group were AS by 6 months. All controls were sensitive to aspirin with similar platelet aggregation and 11-dehydroTxB2 to those in the AS group.
  
  
  CONCLUSIONS
  Aspirin resistance is a transient phenomenon during the early postoperative period in approximately 30% of patients undergoing OPCAB.
authors.affiliation: Department of Cardiovascular Surgery, Tianjin Medical University General Hospital, Tianjin, PR China.
authors.forename: Zanxin
authors.initials: Z
authors.lastname: Wang
authors.forename: Fei
authors.initials: F
authors.lastname: Gao
authors.forename: Jianlong
authors.initials: J
authors.lastname: Men
authors.forename: Jing
authors.initials: J
authors.lastname: Ren
authors.forename: Paul
authors.initials: P
authors.lastname: Modi
authors.forename: Minxin
authors.initials: M
authors.lastname: Wei
mesh_terms: D000368:Aged; D001241:Aspirin / Q000008:administration & dosage / Q000494:pharmacology*; D015415:Biomarkers / Q000652:urine; D016022:Case-Control Studies; D047549:Coronary Artery Bypass, Off-Pump / Q000009:adverse effects; D004334:Drug Administration Schedule; D004351:Drug Resistance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D010976:Platelet Count; D011182:Postoperative Care / Q000379:methods; D011184:Postoperative Period; D013927:Thrombosis / Q000209:etiology / Q000517:prevention & control; D013929:Thromboxane B2 / Q000031:analogs & derivatives / Q000652:urine
chemical_list: D015415:Biomarkers; D010975:Platelet Aggregation Inhibitors; D013929:Thromboxane B2; C049235:11-dehydro-thromboxane B2; D001241:Aspirin