ANTIPLATELET VERSUS WARFARIN THERAPY - PLATELET, NEUTROPHIL, AND THROMBUS DEPOSITION FOR INTRACORONARY STENTS IN A PORCINE MODEL

Antiplatelet therapy may offer an advantage over warfarin in reducing adverse clinical events after intracoronary stent implantation. The me chanism of this effect has not been elucidated bur platelet adhesion m ay play a predominant role in the process of subacute stent thrombosis . This study compared the effect on platelet, neutrophil, and thrombus deposition of three different anticoagulation regimens (aspirin/warfa rin vs aspirin/ticlopidine vs aspirin alone) after intracoronary stent ing in juvenile swine. Thirty stents were deployed in 15 juvenile farm swine randomized to one of 3 anticoagulation protocols: aspirin 325 m g/day; aspirin 325 mg/day and ticlopidine 500 mg/day; aspirin 325 mg/d ay and warfarin 0.1 mg/kg/day. Autologous platelets were labeled using (111)lndium-oxime and a slotted tube metal stent was deployed using a high pressure balloon. Platelet deposition in the stented segment was determined at 24 hours. Each segment was analyzed by light microscopy to document apr injury score; mean and maximum thrombus deposition pe r strut wet-e measured; and neutrophils were counted on each metal str ut and in the vessel wall. Platelet deposition at 24 hours was signifi cantly higher in the aspirin/warfarin group (3.69 +/- 1.16 x 10(8) plt s/cm(2)) than in the aspirin/ticlopidine (1.74 +/- 0.45 x 10(8) plts/c m(2), P = 0.0009) or aspirin (2.42 +/- 2.13 x 10(8) plts/cm(2), P = 0. 03) groups. There was no significant difference between the aspirin an d aspirin/ticlopidine groups (P = 0.9). Mean thrombus area per strut w as significantly greater in the aspirin/warfarin group (0.027 +/- 0.00 6 mm(2)) compared to the aspirin/ticlopidine group (0.017 +/- 0.002 mm (2), P = 0.002). The majority of the thrombus (79%) but minority of ne utrophils (24%) were found on the stent struts. In this coronary stent model, warfarin given with aspirin was associated with greater thromb ogenicity and more platelet deposition than either aspirin/ticlopidine or aspirin alone.