Experimental Study of Thrombogenicity and Foreign Body Reaction Induced by Heparin-Coated Coronary Stents

Abstract

Background Results of recent randomized clinical trials have revealed a significant reduction in angiographic restenosis rate when adjunctive stenting was performed after conventional coronary balloon angioplasty. The thrombogenicity of metal stents, however, remains a concern. In the present study, we compare the thrombogenicity of heparin-coated coronary stents with that of bare metallic coronary stents. Methods and Results Thrombogenicity of metallic coronary stents (four heparin-coated and eight bare stents) was studied in a rat arteriovenous shunt model with the use of ¹²⁵ I-labeled fibrinogen and ⁵¹ Cr-labeled platelets. Total clot weight after 30-minute follow-up was significantly lower in the heparin-coated stents compared with the bare stents (8.1±3.7 versus 25.8±4.6 mg; P <.001). Relative ¹²⁵ I and ⁵¹ Cr activities in the stents were significantly higher in the bare stents than in the heparin-coated stents ( ¹²⁵ I, 1.03±0.43 versus 0.18±0.04, P =.003; ⁵¹ Cr, 17.5±6.8 versus 4.4±1.0, P =.004). Subsequently, heparin-coated and bare stents were randomly implanted in the right coronary artery of 20 domestic pigs. Angiographic parameters were similar between both groups at baseline and after 6-week follow-up. Morphometry also did not show a significant difference in lumen area (bare, 1.03±0.83 mm ² ; heparin-coated, 1.12±0.73 mm ² ; P =NS) or neointimal hyperplasia (bare, 1.01±0.81 mm ² ; heparin-coated, 1.21±0.57 mm ² ; P =NS). Conclusions Heparin coating of metallic coronary stents decreases their thrombogenicity but does not improve late vessel patency and neointimal hyperplasia at follow-up in a porcine coronary model.