Acute and chronic effects of self-expanding nitinol stents in porcine coronary arteries

Background: There is a paucity of experimental data regarding self- expanding stents. This study evaluated the acute and chronic effects of CardioCoil(TM), a self-expanding nitinol coil stent, in porcine coronary arteries. Methods: Twenty-three self-expanding nitinol stents were implanted without associated balloon angioplasty in normal coronary arteries of 12 pigs, which were serially sacrificed up to 6 months. Angiographic and histologic analyses were performed to evaluate the deployment characteristics, patency rates, neointimal response, and unique features of the self-expanding nature of the CardioCoil(TM) stent. Results: All stents were successfully deployed and remained patent acutely. Three undersized stents migrated proximally and there was one episode of subacute thrombosis in an oversized stent. The remaining stents were patent throughout the survival period and neointimal responses were favorable for up to 6 months (all mean neointima < 200 μm up to 6 months). There was evidence of continuing stent expansion over time (stent diameter 2.85 ± 0.78 mm immediately after deployment and 3.24 ± 0.97 mm at follow-up) and the majority of stent struts were in the adventitia by 6 months. Re- endothelization occurred starting one week after implantation and was complete by 8 weeks. Conclusions: This study shows that the CardioCoil(TM) self-expanding nitinol coil stent, is associated with favorable deployment characteristics and potency rates, although appropriate sizing is more crucial than with balloon-expandable stents. More importantly, there appears to be a 'dissociation' between the deep vessel wall injury by the chronic strut expansion process and the neointimal reaction, unlike balloon- expandable stents.