Effects of GP IIb/IIIa Receptor Monoclonal Antibody (7E3), Heparin, and Aspirin in an Ex Vivo Canine Arteriovenous Shunt Model of Stent Thrombosis

BACKGROUND: Thrombosis is an important limitation of metallic coronary stents, especially in smaller vessels in which shear rates are high. Monoclonal antibody to platelet glycoprotein IIb/IIIa receptor (7E3) has been shown to inhibit shear-induced platelet aggregation. In this study, we compared the effects of 7E3, heparin, and aspirin on stent thrombosis in an ex vivo arteriovenous shunt model of high-shear blood flow. METHODS AND RESULTS: An ex vivo arteriovenous shunt was created in 10 anesthetized dogs. Control rough-surface slotted-tube nitinol stents (n = 72) expanded to 2 mm in diameter in a tubular perfusion chamber were interposed in the shunt and exposed to flowing arterial blood at a shear rate of 2100s-1 for 20 minutes. The animals were treated with intravenous murine 7E3 (Fab')2 (0.2, 0.4, and 0.8 mg/kg), heparin (100 U/kg), or aspirin (10 mg/kg). Effects of the test agents on thrombus weight, platelet aggregation, platelet P-selectin expression, bleeding time, and activated clotting time (ACT) were quantified. 7E3 reduced stent thrombosis by 95% (20 +/- 1 to 1 +/- 1 mg, P < .001) and platelet aggregation by 94% (14 +/- 2 to 1 +/- 1 omega, P < .001) at the highest dose (0.8 mg/kg). 7E3 significantly prolonged bleeding time but had no effect on ACT and platelet P-selectin expression. Heparin prolonged ACT but had no significant effect on stent thrombosis or platelet aggregation. Aspirin, although it inhibited platelet aggregation by 65%, had no effect on stent thrombosis (19 +/- 2 versus 20 +/- 1 mg in controls). CONCLUSIONS: 7E3 produced a dose-dependent inhibition of acute stent thrombosis under high-shear flow conditions. Stent thrombosis was resistant to heparin and aspirin. Thus, 7E3 may be an effective agent for preventing stent thrombosis.