RESTENOSIS FOLLOWING PLACEMENT OF AN INTRACORONARY HEPARIN TREATED TANTALUM STENT IN THE HYPERLIPIDEMIC MINIATURE SWINE MODEL

Restenosis persists as an important factor limiting a favorable long t erm outcome following mechanical revascularization. The objective of t he present study was to compare the effects of an intracoronary hepari n treated tantalum prototype stent and balloon angioplasty on intimal hyperplasia, luminal diameter, and thrombosis in a porcine restenosis model. Male miniswine maintained on a high cholesterol diet and 325 mg aspirin per day underwent cardiac catheterization and oversized ballo on injury to the right and left circumflex coronary arteries. Two week s later one artery was either balloon injured again or implanted with a stent. No additional anticoagulation following stent placement was g iven, however aspirin was continued throughout the study. At four week s, the coronary arteries were harvested and prepared for histologic ex amination and blinded quantitative morphometric analysis. The prototyp e stent was successfully deployed in 10 coronary arteries. Histologica l examination at explant revealed no evidence for thrombus or platelet aggregation. The angiographic luminal diameter of stented vessels was not significantly different from the diameter measured prior to impla ntation. In contrast, the angiographic diameter of balloon injured ves sels was significantly decreased (4.4 +/- 0.4 mm(2), balloon injured, vs. 5.8 +/- 3.3 mm(2), control; p < 0.05). Stented arteries showed sig nificantly more intimal hyperplasia, compared to balloon injured vesse ls (2.99 +/- 0.58 mm(2) intimal area, stented arteries vs. 0.38 +/- 0. 15 mm(2) intimal area, control arteries; p < 0.05). In conclusion, hep arin treated tantalum wire prototype intracoronary stents were success fully deployed in swine coronary arteries with no evidence for thrombu s formation. Despite a significant intimal response, luminal diameter was preserved in stented vessels. The data suggest that a heparin trea ted tantalum wire prototype intracoronary stent may be an effective me thod of coronary revascularization that results in the preservation of luminal diameter without thrombotic occlusion.