title: Large early variation of residual platelet reactivity in Acute Coronary Syndrome patients treated with clopidogrel: results from Assessing Platelet Activity in Coronary Heart Disease (APACHE).
abstract: BACKGROUND
  There is a large inter-individual variation in response to clopidogrel treatment and previous studies have indicated higher risk of thrombotic events in patients with high residual platelet reactivity (HRPR), but the optimal time-point for testing is not established. The aim of this study was to investigate the optimal time-point for aggregometry testing and the risk of major adverse cardiac events associated with HRPR.
  
  
  RESULTS
  We included 125 patients with ACS (73 with STEMI, and 71 received abciximab). The prevalence of HRPR varied substantially over time. The rate of HRPR in patients treated and not treated with abciximab were 43% vs 67% (p=0.01) before, 2% vs 23% (p=0.001) 6-8h after, 8% vs 9% (p=0.749) 3days after, and 23% vs 12% (p=0.138) 7-9 days after loading dose of clopidogrel. We found HRPR in 18% of the patients but only four ischemic events during 6months follow-up, with no significant difference between HRPR patients compared to the rest of the population. There were 3 TIMI major bleedings, all of which occurred in the low residual platelet reactivity (LRPR) group.
  
  
  CONCLUSIONS
  There is a large variation in platelet reactivity over time, also depending on adjunctive therapy, which has a large impact on optimal time-point for assessment. We found HRPR in almost 1 in 5 patients, but very few MACE, and not significantly higher in HRPR patients. In a contemporary ACS population, with low risk for stent thrombosis, the predictive value of HRPR for ischemic events will probably be low.
authors.affiliation: Department of Cardiology and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden. Electronic address: joakim.alfredsson@liu.se.
authors.forename: Joakim
authors.initials: J
authors.lastname: Alfredsson
authors.affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
authors.forename: Tomas L
authors.initials: TL
authors.lastname: Lindahl
authors.affiliation: Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
authors.forename: Kerstin M
authors.initials: KM
authors.lastname: Gustafsson
authors.affiliation: Department of Cardiology and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Janzon
authors.affiliation: Department of Cardiology and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Lena
authors.initials: L
authors.lastname: Jonasson
authors.affiliation: Department of Cardiology and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Logander
authors.affiliation: Department of Cardiology and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Lennart
authors.initials: L
authors.lastname: Nilsson
authors.affiliation: Department of Cardiology and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Swahn
mesh_terms: D054058:Acute Coronary Syndrome / Q000175:diagnosis* / Q000188:drug therapy* / Q000503:physiopathology; D000368:Aged; D000077144:Clopidogrel; D005260:Female; D006801:Humans; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects*; D010976:Platelet Count / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000627:therapeutic use; D016896:Treatment Outcome
chemical_list: D000077144:Clopidogrel; D013988:Ticlopidine