Higher on-treatment platelet reactivity and more bleeding complications in the elderly: insight from the ARCTIC study

Abstract

Background: The ARCTIC study showed no significant improvement in clinical outcomes with platelet function monitoring and treatment adjustment before and after coronary stenting. The objective of this study was to evaluate, in this population, on treatment platelet reactivity and occurrence of ischemic and bleeding complications compared to a younger population. Results: Of the 2440 patients randomized in the ARCTIC study, 384 were>75 yrs (15.74%). Mean age was 79.6±3 yrs, with more women (32.3% vs. 16.8%), more frequent hypertension (78.9% v. 59.2%) and lower body weight (73.06±13.1 vs. 79.99±14.86kg) in the elderly compared with younger patients (p for all <0.001). At the time of stent implantation, high on-thienopyridine platelet reactivity was more frequent in the elderly than in younger patients (44.6% versus 32.6%, p=0.001) while no difference was observed for high on-aspirin platelet reactivity (8.7% versus 7.6%, p=ns). Intensification of antiplatelet therapy was more frequently performed using clopidogrel reloading (21.9% versus 16.9%, p=0.02) and less frequently by switching to a more potent P2Y12 inhibition strategy like pra-sugrel (3.1% versus 8.4%, p=0.0004). As a consequence, high on-thienopyridine platelet reactivity remained significantly higher in the elderly than in younger patients during the maintenance phase (21.8% versus 14.4%, p=0.001). At one-year follow-up, major and minor bleeding events were more frequent in the elderly than in younger patients (HR 1.72; 95% CI 1.07-2.78, p=0.03) whereas there was no difference in the rate of primary endpoint (death, Myocardial infarction, stent thrombosis, stroke or transient ischemic attack, urgent revascularization) HR 1.02 [0.84; 1.23], p=0,86, but there were more deaths in the elderly (HR 2.05; 95% CI 1.08-3.87, p=0.03). Conclusion: Despite having higher on-treatment platelet reactivity and a lesser oral aggressive strategy of antiplatelet treatment compared with younger patients, the elderly had more frequent bleeding events.