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RESEARCH PRODUCT

Comparison of antiplatelet effects of aspirin, ticlopidine, or their combination after stent implantation.

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Background —This study was performed to analyze the influence of either aspirin, ticlopidine, or their combination on platelet activation and aggregation parameters after stent implantation. Methods and Results —Sixty-one patients with successful implantation of a single Palmaz-Schatz stent in a native coronary artery were randomly assigned to either group A (aspirin 300 mg/d+ticlopidine 2×250 mg/d), group B (ticlopidine 2×250 mg/d), or group C (aspirin 300 mg/d). Platelet activation was evaluated on days 1, 7, and 14 by flow cytometry measurement of expression of CD62p (p-selectin) and the binding of fibrinogen to the platelet surface glycoprotein IIb/IIIa receptor. Platelet aggregation was induced by addition of ADP or collagen. Differences between treatment groups were compared by ANOVA. Between days 1 and 14, we observed a significant decrease in collagen-induced platelet aggregation in group A (62.2±2.5% versus 36.9±3.1%), whereas an increase was seen in group B (58.3±2.5% versus 67.7±3.2%) and no change was seen in group C ( P <.0001). The ADP-induced aggregation declined significantly in group A (74.7±1.4% versus 55.3±2.6%), whereas a delayed reduction was seen in group B (72.0±3.0% versus 52.6±4.2%) and no change was seen in group C ( P =.0017). The CD62p expression declined significantly in groups A (68.2±2.7% versus 41.3±2.7%) and B (64.8±2.9% versus 39.3±3.5%) but not in group C ( P <.0001). Moreover, the fibrinogen binding decreased significantly in group A (61.0±4.3% versus 36.3±4.2%) and with delay in group B (58.3±2.2% versus 39.4±3.0%), whereas no alterations were seen in group C ( P =.012). Conclusions —Our results demonstrate synergistic and accelerated platelet inhibitory effects of ticlopidine plus aspirin in patients after stent implantation compared with a monotherapy with either ticlopidine or aspirin alone.