title: Patients with previous definite stent thrombosis have a reduced antiplatelet effect of aspirin and a larger fraction of immature platelets.
abstract: OBJECTIVE
  This study sought to evaluate the platelet response to aspirin and the immature platelet fraction in patients with previous stent thrombosis (ST).
  
  
  BACKGROUND
  ST is a potentially fatal complication of coronary stenting. A reduced platelet response to aspirin increases the risk of cardiovascular events.
  
  
  METHODS
  We included 117 patients previously undergoing percutaneous coronary intervention. A total of 39 patients had suffered ST and 78 patients served as controls matched at a 1:2 ratio with respect to age, sex, stent type, and percutaneous coronary intervention indication. All patients were treated with aspirin 75 mg once daily. Platelet function was assessed by multiple electrode aggregometry in citrated and hirudinized blood and by VerifyNow Aspirin Assay (Accumetrics, San Diego, California). Flow cytometric determination of the immature platelet fraction was performed to evaluate platelet turnover. Platelet activation was evaluated by soluble serum P-selectin. Compliance was confirmed by serum thromboxane B(2).
  
  
  RESULTS
  All patients were fully compliant, which was confirmed by suppressed levels of serum thromboxane B(2). Platelet aggregation was increased in patients with previous ST when assessed by multiple electrode aggregometry induced by collagen (p(citrated blood) = 0.003; p(hirudinized blood) < 0.0001) and by arachidonic acid (p(citrated blood) = 0.16; p(hirudinized blood) = 0.04), respectively. Similarly, platelet aggregation assessed by VerifyNow was higher in ST cases (p = 0.12). A trend toward an increased immature platelet fraction among cases was seen (p = 0.13), whereas P-selectin levels (p = 0.56) did not differ between groups.
  
  
  CONCLUSIONS
  Overall, patients with previous ST had a reduced antiplatelet effect of aspirin, which might be explained by an increased platelet turnover.
authors: Department of Cardiology, Aarhus University Hospital, Skejby, Denmark.
authors: Morten
authors: M
authors: Würtz
authors: Erik L
authors: EL
authors: Grove
authors: Lise N
authors: LN
authors: Wulff
authors: Anne K
authors: AK
authors: Kaltoft
authors: Hans H
authors: HH
authors: Tilsted
authors: Lisette O
authors: LO
authors: Jensen
authors: Anne-Mette
authors: AM
authors: Hvas
authors: Steen D
authors: SD
authors: Kristensen
mesh_terms: D000368:Aged; D015906:Angioplasty, Balloon, Coronary / Q000009:adverse effects / Q000295:instrumentation*; D001241:Aspirin / Q000627:therapeutic use*; D015415:Biomarkers / Q000097:blood; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D003324:Coronary Artery Disease / Q000097:blood / Q000188:drug therapy / Q000628:therapy*; D003718:Denmark; D004351:Drug Resistance; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016014:Linear Models; D008297:Male; D055118:Medication Adherence; D008875:Middle Aged; D019007:P-Selectin / Q000097:blood; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D010976:Platelet Count; D010979:Platelet Function Tests; D012189:Retrospective Studies; D015607:Stents; D013927:Thrombosis / Q000097:blood / Q000209:etiology / Q000517:prevention & control*; D013929:Thromboxane B2 / Q000097:blood; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D019007:P-Selectin; D010975:Platelet Aggregation Inhibitors; D013929:Thromboxane B2; D001241:Aspirin