Background/objective: To test the hypothesis that circulating platelets display evidence of interactions with atherogenesis, platelet capacity to express P-selectin and propensity for spontaneous microaggregation in vitro were measured in samples from normal donors (N), patients with asymptomatic advanced coronary calcification (CC) or acute coronary syndromes (AC). To measure the effect of angioplasty on platelet function, samples obtained before, 30 min after and 24 h after angioplasty were compared. Patients/methods: Platelet P-selectin was measured after maximal stimulation with thrombin. Microaggregation was measured as a platelet count deficit in citrate-anticoagulated platelet-rich plasma (PRP) relative to EDTA-anticoagulated blood. Results: P-selectin expression was significantly lower for platelets from patients with either AC or CC compared to normals. In addition, platelets from AC and CC patients have a significantly greater propensity to form microaggregates in citrate anticoagulant. After angioplasty, the PRPplatelet count decreased transiently. Conclusion: Both acute unstable and chronic stable coronary disease are associated with an increased share of platelets unable to express P-selectin and an increased share of platelets that microaggregate in citrate anticoagulant. The genesis of these platelet characteristics is not fully explained by focal acute arterial injury and may reflect exposure to systemic atherosclerosis or the atherogenic process.
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