title: Factors influencing platelet reactivity in patients undergoing coronary artery bypass surgery.
abstract: OBJECTIVE
  Because coronary artery bypass graft (CABG) surgery is associated with a high turnover of platelets, assessment of platelet function should enable assessment of the effect of young (RNA-containing) platelets on platelet reactivity. This study was designed to assess platelet reactivity 1 day after CABG in patients treated previously with clopidogrel or ticagrelor.
  
  
  METHODS
  Patients (n=18) with acute coronary syndrome who required urgent CABG and had been treated for up to 2 days before surgery with aspirin plus clopidogrel (n=13) or aspirin plus ticagrelor (n=5) were enrolled. Care was not altered by participation, which entailed review of medical records and taking one sample of blood 1 day after surgery. The percentage of RNA-containing platelets was quantified using thiazole orange, and platelet function was assessed by flow cytometry.
  
  
  RESULTS
  Young platelets constituted, on average, 24% of platelets (range 4-54%) and were more likely to be activated in the absence or presence of an agonist (P<0.001). Differences between RNA-containing (young) and non-RNA-containing platelets were evident in patients treated previously with clopidogrel (P<0.001), whereas a nonsignificant trend was apparent in patients treated previously with ticagrelor. A high but variable prevalence of young platelets was seen 1 day after CABG.
  
  
  CONCLUSIONS
  Young platelets were more reactive and, consistent with the irreversible binding of clopidogrel to P2Y12, this effect was more pronounced after treatment with clopidogrel. The reversible binding of ticagrelor to the platelet P2Y12 receptor may be advantageous in patients with a high platelet turnover.
authors.affiliation: Department of Medicine, Cardiology Unit, Cardiovascular Research Institute, University of Vermont, Burlington, Vermont, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Schneider
authors.forename: Sreedivya
authors.initials: S
authors.lastname: Chava
mesh_terms: D054058:Acute Coronary Syndrome / Q000097:blood / Q000175:diagnosis / Q000601:surgery*; D000241:Adenosine / Q000008:administration & dosage / Q000031:analogs & derivatives; D000368:Aged; D001241:Aspirin / Q000008:administration & dosage; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D000077144:Clopidogrel; D001026:Coronary Artery Bypass / Q000009:adverse effects; D004359:Drug Therapy, Combination; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*; D010979:Platelet Function Tests; D011237:Predictive Value of Tests; D058921:Purinergic P2Y Receptor Antagonists / Q000008:administration & dosage*; D000077486:Ticagrelor; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D010975:Platelet Aggregation Inhibitors; D058921:Purinergic P2Y Receptor Antagonists; D000077144:Clopidogrel; D000077486:Ticagrelor; D000241:Adenosine; D013988:Ticlopidine; D001241:Aspirin