A Bigger Look Into the "Therapeutic Window" of Platelet Reactivity to Adenosine Diphosphate.

A decade ago, small observational studies using light transmittance aggregometry suggested that post-stenting ischemic event occurrences were not linearly related to ontreatment platelet reactivity (OPR) levels but instead largely occurred above a moderate threshold level (1,2). For example, in the CREST (Carotid Revascularization Endarterectomy Versus Stenting Trial) study of 20 patients with previous stent thrombosis (ST) and 100 age-matched patients without ST, >40% maximal platelet aggregation in response 20 mM adenosine diphosphate (ADP) was associated with ST (3). Subsequently, a number of studies using various platelet function assays including the most widely used VerifyNow P2Y12 assay demonstrated similar OPR cutoff values associated post-stenting ischemic event occurrences and termed an upper cutoff value as high OPR (HPR) (4). It was hypothesized that adequate protection against ischemic events with antiplatelet therapy is achieved by low to moderate levels of OPR in the majority of patients, whereas markedly low levels of OPR are associated with greatly increased bleeding risks, a so-called