Advanced age and high-residual platelet reactivity in patients receiving dual antiplatelet therapy with clopidogrel or ticagrelor

Background: The aim of the present study was to evaluate the impact of age on platelet function and the occurrence of high residual on-treatment platelet reactivity (HRPR) in patients treated with dual antiplatelet therapy (DAPT) using acetylsalicilic acid (ASA) and clopidogrel or ticagrelor. Methods: Patients treated with DAPT (ASA and clopidogrel or ticagrelor) were scheduled for platelet function assessment at 30-90 days post-discharge. By whole blood impedance aggregometry, HRPR was considered for ASPI test values > 862 AU*min (for ASA) and adenosine diphosphate (ADP) test values > 417 AU*min (for ADP antagonists). Elderly patients were defined as those aged >= 70 years. Results: Among 494 patients on DAPT, 224 (45.3%) were >= 70 years old. ADP-mediated platelet aggregation increased with decades of age (279.3 +/- 148.6 vs. 319.6 +/- 171.1 vs. 347.3 +/- 190.1 vs. 345.7 +/- 169.2), whereas no difference was observed for ASA response. A reduced effectiveness of ADP antagonists was observed among elderly patients; in fact, among the 117 patients displaying HRPR (23.7%), a higher prevalence was observed among patients over 70 years old (30.4% vs. 18.1%; adjusted odds ratio (OR) [95% confidence interval (CI)] = 2.19 [1.29-3.71]). Similar results were obtained among the 266 clopidogrel-treated patients (38.5% vs. 27.9%; adjusted OR [95% CI] = 2.91 [1.46-5.8]) and in the 228 patients receiving ticagrelor (19.1% vs. 8.1%; adjusted OR [95% CI] = 2.55 [1.02-8.59]). Conclusion: In patients receiving dual antiplatelet therapy, advanced age is independently associated with a reduced effectiveness of ADP antagonists and a higher rate of HRPR with both clopidogrel and ticagrelor.