Circadian variations of platelet reactivity on clopidogrel in patients treated with elective percutaneous coronary intervention.

Evidence assessing potential diurnal variations of platelet reactivity in patients on clopidogrel treated with elective percutaneous coronary intervention (PCI) for chronic coronary syndrome (CCS) are currently lacking. We prospectively enrolled 15 patients affected by stable coronary artery disease (CAD) previously treated with elective PCI and on clopidogrel for at least 8 days (administered at 8 a.m.). A significant heterogeneity in diurnal levels of ADP-dependent platelet aggregation was found (p = 0.0004), with a peak of platelet reactivity occurring at the 6 a.m. assessment, which resulted significantly increased compared to the afternoon (6 p.m.) evaluation (255 ± 66 vs 184 ± 67, p = 0.002). In addition, at the early-morning evaluation a considerably high proportion of patients with high platelet reactivity (53.3%) were observed. In conclusion, clopidogrel-induced platelet inhibition in patients with CCS after elective PCI follows a circadian rhythm, thus suggesting that a consistent and durable antiplatelet inhibition is often failed with standard clopidogrel administration at morning.