Dual antiplatelet therapy with aspirin and clopidogrel is the cornerstone of treatment after percutaneous coronary intervention (PCI). Platelet responsiveness to these two agents is not well known in elderly patients. We sought to evaluate aspirin and clopidogrel response in elderly patients soon after PCI and on chronic maintenance treatment.

We prospectively included 93 elderly patients (≥75 years) who underwent PCI from January 2008 to April 2009. All patients were treated with aspirin and clopidogrel. We used a standardized point of care assay VerifyNow^® aspirin and VerifyNow^® clopidogrel P2Y12 to measure aspirin and clopidogrel responsiveness with cut-offs previously validated in clinical trials. Measurements were performed in-hospital after PCI (T1) and 5–6 weeks later (T2) when the patients had been on maintenance therapy (75mg aspirin plus 75mg clopidogrel once a day) for at least 1 week. Aspirin non/poor responders were found in 10% of patients at T1 and in 14% at T2. Clopidogrel non/poor response was noted in 32% of patients at T1 and in 68% at T2. Changes in platelet reactivity to clopidogrel was significant from T1 to T2 (p-value <0.001), but not significant for aspirin. Multivariate analysis revealed low hematocrit (Ht) to be independently associated with clopidogrel non responsiveness at T1 (OR 2.99; 95% CI 1.04–8.59; p-value = 0.042 for Ht <35%) and T2 (OR 2.74; 95% CI 1.08–6.93; p-value = 0.033 for Ht <40%).

The rate of biological non/poor response to dual antiplatelet therapy in elderly patients soon after PCI was close to that reported in younger patients. In contrast, there was high residual platelet reactivity under chronic treatment with 75mg of clopidogrel (almost two-thirds).