REDUCTION IN THROMBOTIC EVENTS WITH HEPARIN-COATED PALMAZ-SCHATZ STENTS IN NORMAL PORCINE CORONARY-ARTERIES

Background The use of stents improves the result after balloon coronar y angioplasty. Thrombogenicity of stents is, however, a concern. In th e present study, we compared stents with an antithrombotic coating wit h regular stents. Methods and Results Regular stents were placed in co ronary arteries of pigs receiving no aspirin (group 1; n=8) or aspirin over 4 weeks (group 2, n=10) or 12 weeks (group 3, n=9). Stents coate d with heparin (antithrombin III uptake, 5 pmol/stent) were placed in 7 pigs that did not receive aspirin (group 4). The other animals recei ved aspirin and coated stents with a heparin activity of 12 pmol antit hrombin III/stent (group 5, n=10) or 20 pmol/stent (group 6, n=10; gro up 7, n=10). Quantitative arteriography was performed at implantation and after 4 (groups 1, 2, and 4 through 6) or 12 weeks (groups 3 and 7 ). In an additional 5 animals, five regular and five coated stents (20 pmolistent) were placed and explanted after 5 days for examination of the early responses to the implants. Thrombotic occlusion of the regu lar stent occurred in 9 of 27 in groups 1 through 3. However, in 0 of 30 of the animals receiving high activity heparin-coated stents (group s 5 through 7), thrombotic stent occlusion was observed (P<.001). Hist ological analysis at 4 weeks showed that the neointima in group 6 was thicker compared with its control group 2 (259+/-104 and 117+/-36 mu m , P<.01), but at 12 weeks the thickness was similar (152+/-61 and 198/-49 mu m, respectively). Comparison at 5 days suggested delayed endot helialization of the coating. Conclusions High-activity heparin coatin g of stents eliminates subacute thrombosis in porcine coronary arterie s.