In vitro model to test the thrombogenicity of coronary stents

Thrombotic occlusion is a major complication limiting the application of stents in coronary arteries. In an in vitro model we investigated the thrombogenicity of different stent materials and several medical regimens to prevent thrombotic occlusion. Experiments were conducted in a closed system of silicon tubing with circulating citrated platelet rich plasma of healthy volunteers (n = 7) and of patients (n = 7 for each condition). Patients were either treated with phenprocoumon or with high or low dose heparin in combination with aspirin alone (100 mg) or aspirin (990 mg) plus dipyridamole (225 mg). After placement of tantalum wire stents into the system platelet aggregates were visible after 13.5 +/- 3.0 min, and occlusion occurred after 15.0 +/- 3.5 min. Similarly, with implanted stainless steel stents aggregation was seen after 13.0 +/- 3.5 min and thrombosis occurred after 14.5 +/- 3.5 min (p < 0.001 vs control without stent). Microscopic examination revealed combined platelet fibrin thrombi occluding the lumen. Platelet components predominately covered stent wires, particularly at crossing points. In all experiments high-dose heparin prevented platelet aggregate formation and stent occlusion independently of additional aspirin or aspirin plus dipyridamole; perfusion time > 60 min (p < 0.001 vs no heparin). Low-dose heparin could not prevent clotting. With aspirin alone aggregates were visible after 16.0 +/- 4.0 min and clotting occurred after 23.0 +/- 5.0 min. In combination with dipyridamole aggregates were visible after 15.5 +/- 5.0 min and clotting after 21.0 +/- 4.0 min (NS vs aspirin alone). Phenprocoumon prevented platelet aggregate formation and stent occlusion; perfusion time > 60 min.(ABSTRACT TRUNCATED AT 250 WORDS)