BACKGROUND: Antiplatelet therapy is a cornerstone prevention strategy for secondary ischemic stroke (IS) and transient ischemic attack (TIA). Yet, a proportion of patients who receive antiplatelet therapy experience recurrent ischemic cerebrovascular events. A recent meta-analysis found an increased risk of recurrent stroke in clopidogrel- or aspirin-treated patients with ischemic stroke who had high on-treatment platelet reactivity (HTPR). Few studies have focused specifically on clopidogrel HTPR. Therefore, the aim of this study was to examine the relationship between clopidogrel HTPR and recurrent ischemic events in a population of Danish patients with IS.

METHODS: We performed a prospective observational study to evaluate the relationship between HTPR defined as platelet reaction units >208 and a composite primary endpoint of recurrent stroke, TIA, acute myocardial infarction (AMI), or vascular death over a 2-year follow-up period.

RESULTS: A total of 142 patients were included in the final statistical analysis, but only 3 patients (2.1%) demonstrated clopidogrel HTPR. The median time of on-treatment platelet testing was 75 days. Recurrent IS, TIA, AMI, or vascular death occurred in 14 patients (10%). Of these, 1 new ischemic event (AMI) occurred in a HTPR patient. There was no difference in the frequency of new ischemic events between the HTPR and non-HTPR groups (P = .27); moreover, the number of patients with HTPR was too small for statistical analysis.

CONCLUSIONS: Clopidogrel HTPR does not seem to be a major contributor to recurrent ischemic events in Danish ischemic stroke patients.