Two distinct mechanisms are involved in stent thrombosis under flow conditions

The mechanism of stent thrombosis was evaluated by a flow chamber model. A Palmaz-Schatz stent was placed on glass surfaces coated with type I collagen in a parallel-plate flow chamber. Platelets were rendered fluorescent with mepacrine and whole blood was perfused through the chamber. Platelet thrombi formed around the implanted stents were continuously recorded by epi-fluorescent video-microscopy. Platelet thrombi appeared on the collagen surface within a few minutes in the absence of function blocking monoclonal antibodies. Antibody blocking vWF interaction with GP Ib f completely inhibited the platelet thrombi around the stent, but had no effect on platelet thrombus formation in the space between the stents and collagen, while both were inhibited by anti-GP IIb/IIIa. Our results suggest that two distinct mechanisms, one mediated by vWF interaction with GP Ib f occurring at high shear rates, and the other mediated exclusively by GP IIb/IIIa occurring at low shear rates, are involved in the process of platelet thrombus formation in the presence of stents.