Residual platelet reactivity and outcomes with 5mg prasugrel therapy in elderly patients undergoing percutaneous coronary intervention.

BACKGROUND: In acute coronary syndrome (ACS) patients older than 75years old, prasugrel 10mg maintenance therapy has shown less clinical efficacy and higher risk of bleeding. In patients older than 75years, a prasugrel dose of 5mg should be used if treatment is deemed necessary. OBJECTIVE: The aim of this study was to compare platelet reactivity and outcomes in elderly patients receiving prasugrel 5mg therapy with non-elderly patients receiving prasugrel 10mg therapy. METHODS AND RESULTS: Consecutive ACS patients undergoing percutaneous coronary intervention (PCI) treated with prasugrel were included. Of 718 patients, 228 (32%) had ≥75years and received prasugrel 5mg/day. Residual platelet reactivity (RPR) was 47±18% and 36±16% in the elderly and non-elderly group, respectively (p=0.001). High RPR (≥70%) was found in 9% and 2% (p=0.0001) in elderly and non-elderly patients, respectively. In the 6-month follow-up, there was no difference in mortality, stent thrombosis, and reinfarction rates between the 2 groups but a higher rate of TIMI minor bleeding (7.9% vs 2.4%; p=0.001) in elderly as compared with younger patients. Age≥75years was independently associated with bleeding events (HR 2.162 [1.105-4.229]; p=0.024). CONCLUSIONS: Elderly patients receiving prasugrel 5mg are more likely to experience high RPR than younger patients treated by prasugrel 10mg. Despite the use of a reduced prasugrel maintenance dose and a higher level of RPR, elderly patients show increased risk of bleeding during prasugrel therapy as compared to younger patients.