Not-high before-treatment platelet reactivity in patients with STEMI: prevalence, clinical characteristics, response to therapy and outcomes.

Platelet reactivity (PR) has been indicated as a pathophysiological key element for ST-Elevation Myocardial Infarction (STEMI) development. Patients with not-high before-treatment platelet reactivity (NHPR) have been poorly studied so far. The aim of this study is to investigate the prevalence, clinical characteristics, response to therapy and outcomes of baseline prior to treatment NHPR among patients with STEMI undergoing primary PCI.We analyzed the data from 358 STEMI patients with assessment of PR by VerifyNow before P2Y12 inhibitor loading dose (LD). Blood samples were obtained at baseline, and after 1 hour, 2 hours, 4-6 hours and 8-12 hours after LD. High platelet reactivity (HPR) was defined as Platelet Reactivity Unit values ≥208, while patients with values <208 at baseline were defined as having NHPR.Overall, 20% patients had NHPR. Age and male gender both resulted independent predictors of NHPR, even after propensity score adjustment. The percentage of inhibition of PR after ticagrelor or prasugrel LD was similar between HPR and NHPR patients at each time point. However, patients with HPR showed worse in-hospital clinical outcomes, and the composite adverse outcome endpoint of death, reinfarction, stroke, acute kidney injury or heart failure was significantly higher (10.0% vs 1.4%; p = .017) as compared with the NHPR group.In conclusion, a significant proportion of patients presenting with STEMI has a baseline NHPR that is associated with better in-hospital outcomes as compared with patients with HPR. Further studies are needed to better elucidate the potential therapeutic implications of NHPR in terms of secondary prevention.