Impact of the Degree of Peri-Interventional Platelet Inhibition After Loading With Clopidogrel on Early Clinical Outcome of Elective Coronary Stent Placement

Background: Platelet responses after loading with clopidogrel are highly variable. The impact of this variability on the peri-interventional risk of patients undergoing PCI has not been investigated prospectively.

Objectives: Our prospective study test the hypothesis that the 30-day clinical outcome of elective percutaneous catheter intervention (PCI) differs between strata defined by quartiles of platelet aggregation after loading with 600mg of clopidogrel. Further on we will investigate impact of the variability in platelet response on long-term outcome after PCI.

Methods: Our study will include consecutive patients undergoing elective coronary stent placement. Before PCI, patients receive a loading dose of 600mg of clopidogrel followed by 75mg daily. Primary end point is the 30-day composite of death, myocardial infarction and target lesion revascularization (MACE). Platelet aggregation was assessed immediately before PCI by optical aggregometry (5µmol/L ADP).

Sample size calculation was based on ISAR-REACT which comprised a cohort with similar selection criteria and treatment strategy. Thus, we assume an incidence of the primary end point of 4.2%. We design our study to test the hypothesis that the incidence of the primary end point differed by quartiles of ADP-induced platelet aggregation. We intend to have a power of 0.80 to detect an effect size of 0.015 (for example 3-fold risk in 4th quartile) with a 2-sided P-value less than 0.05. With these assumptions we obtain a sample size of at least 748 and aime for a cohort of 800.