Relation between ticagrelor response and levels of circulating reticulated platelets in patients with non-ST elevation acute coronary syndromes.

Antiplatelet responses to clopidogrel and prasugrel are highly variable and subject to significant rates of high on-treatment platelet reactivity (HTPR) after percutaneous coronary intervention (PCI). The proportion of circulating young reticulated platelets (RPs) inversely correlates with responsiveness to both agents. We aimed to determine the relationship between RPs and on-treatment platelet reactivity in ticagrelor-treated patients. Patients with non-ST-elevation acute coronary syndromes (NSTE-ACS) treated with PCI and ticagrelor were tested for platelet reactivity using the VerifyNow P2Y12 assay and multiplate aggregometry. RPs levels were determined using flow cytometry with thiazole orange staining. Tests were performed at 2-4 and 30 days post-PCI. Fifty three patients were included (mean age 62.6 ± 9.8 years, 18.9 % women, 35.8 % diabetes), of which 41 patients (77 %) completed follow-up. Variability in response to ticagrelor was very low according to both assays with no identified cases of HTPR at either time-point. In addition, there were no differences in platelet reactivity, as analyzed by the VerifyNow P2Y12 assay, or in the proportion of RPs between the two time points (p > 0.5). With the multiplate assay, platelet reactivity increased between the two time-points (8.6 ± 6.0 vs. 15.5 ± 11 AU*min; p = 0.0007). There was no significant correlation between RPs and platelet reactivity at both time-points and using both assays (p > 0.5). There were no cases of HTPR up to 30-days post-PCI in patients with NSTE-ACS treated with ticagrelor. In this cohort, no correlation between % RPs and platelet reactivity was observed. Attenuation of RP-induced platelet reactivity as a novel mechanism for ticagrelor's benefit requires further investigation.