Comparison of the endothelial coverage in everolimus and zotarolimus-eluting stents in normal, atherosclerotic, and bifurcation rabbit iliac arteries.

The aim of this study is to evaluate differences in stent endothelial coverage among the second generation of drug-eluting stents. Incomplete stent coverage is one of the major causes of late stent thrombosis. Rabbits fed a normal diet received an everolimus (Xience Prime; EES) and a zotarolimus-eluting stent (Resolute Integrity; R-ZES) in each iliac artery, followed by sacrifice at 14 and 28 days after stent implantation. In addition, a group of atherosclerotic rabbits similarly received EES and R-ZES, and were sacrificed at 28 days. The extent of stent endothelial coverage was assessed by scanning electron microscopy. To evaluate endothelial coverage after bifurcation stenting, rabbits received EES and R-ZES placed with culotte stenting at the iliac bifurcation, followed by sacrifice at 14 and 28 days. In rabbits fed a normal diet, the percent uncovered strut area 14 days after stent implantation was significantly higher in R-ZES than in EES (10.1% (IQR 9.8-15.5) vs. 3.0% (IQR 1.5-9.7), p = 0.03), whereas it was not significantly different at 28-days (3.9% (IQR 0.8-10.3) vs. 1.0% (IQR 0.0-2.8), p = 0.2). In rabbits with induced atheroma, R-ZES also showed less endothelial coverage 28 days after stent implantation (5.3% (IQR 2.2-9.9) vs. 1.1% (IQR 0-6.2), p = 0.03). In the culotte stenting model, the percent uncovered strut area of the proximal overlapped segment was significantly higher in R-ZES at 14 days (15.8% (IQR 14.3-17.7) vs. 8.8% (IQR 8.3-9.8), p = 0.03) and 28 days (9.9% (IQR 4.1-13.9) vs. 2.5% (IQR 1.6-6.7), p = 0.04) after stent implantation. The carina area also showed a better coverage in EES compared with R-ZES. EES showed a better stent endothelial coverage compared with R-ZES after stent implantation in the early phase in normals, in arteries with lipid rich plaque, and in bifurcation stented sites.