Immature platelet fraction and high-on treatment platelet reactivity with ticagrelor in patients with acute coronary syndromes.

Residual high-on treatment platelet reactivity (HRPR) has been associated with a 2-9 fold increased risk of acute ischemic events in patients with acute coronary syndromes or coronary stenting. However, the mechanism of suboptimal platelet inhibition are still poorly understood. Aim of present study was to evaluate the role of the percentage of reticulated platelets on HRPR with ticagrelor. In patients treated with ASA (100-160 mg) and ticagrelor (90 mg twice a day) platelet reactivity and the reticulated platelets fraction (immature platelets fraction, IPF) were assessed at 30-90 days after acute coronary syndrome. Aggregation was assessed by multiple-electrode aggregometry. HRPR was defined as ADP test >417 AU*min. Our population is represented by 190 patients, divided according to tertiles values of IPF (<2.5; 2.5-3.99; ≥4 %). Higher IPF was associated to a larger platelet volume and lower platelets count (p < 0.001), and inversely related with a history of previous coronary revascularization (p = 0.03). Twenty-one out of 190 (11.0 %) patients displayed HRPR. No difference in the levels of circulating IPF was found in patients with or without HRPR (p = 0.25), with no correlation between the rate of reticulated platelets and platelet reactivity at ADP test (r = -0.084, p = 0.26). In fact no association was observed between high levels of IPF and the occurrence of HRPR (adjusted OR[95 % CI] = 0.69[0.34-1,37], p = 0.28), even after correction for baseline differences. In patients treated with ticagrelor, the levels of circulating reticulated platelets assessed at 30-90 days post-ACS are not associated with platelet reactivity or the occurrence of HRPR.