Formation of platelet microaggregates correlates with adverse clinical outcome in patients with coronary artery disease.

Platelet activation plays a pivotal role in the pathogenesis of acute coronary syndromes. Laser-light scattering in a platelet aggregometer was used to evaluate aggregate size and number quantitatively. Small platelet aggregates ultimately develop into medium and then large platelet aggregates. Thus the measurement of small platelet aggregates is important in the evaluation of thrombus formation. We examined the relationship between small platelet aggregates and the occurrence of subsequent cardiovascular events. We followed-up 204 patients (149 men and 55 women, mean age 68 +/- 9 years) with coronary artery disease (CAD) for 48 months. Blood sampling to determine platelet aggregation was performed on the day of hospital discharge. The degree of small platelet aggregates [relative risk 4.34, 95% confidence interval (1.62-11.7), p = 0.004] and low left-ventricular ejection fraction [relative risk 2.88, 95% confidence interval (1.23-6.73), p = 0.015] were independent predictors of the occurrence of cardiovascular events in multivariate Cox hazard analysis. In Kaplan-Meier analysis, the degree of small platelet aggregates correlated with the probability of cardiovascular event occurrence. In patients with CAD, an increase in small platelet aggregates is closely correlated with the future occurrence of cardiovascular events