Strut tissue coverage and endothelial cell coverage: a comparison between bare metal stent platforms and platinum chromium stents with and without everolimus-eluting coating

Aims: In a rabbit denudation model, assess impact of strut thickness on arterial healing by comparing endothelial cell coverage and strut tissue coverage after implantation of bare metal stents of varying thickness; evaluate the effect of an everolimus-eluting stent. Methods and results: Strut tissue coverage and endothelialisation were assessed 14 and 21 days after implantation with scanning electron microscopy quantitation methods and immunostaining against the endothelial cell marker PECAM-1 (CD-31). At 14 days, strut tissue coverage was higher with the stainless steel Liberte stent (88%, 97 mu m) versus Express (77%, 132 mu m). The platinum chromium Element stent with the thinnest strut (81 mu m) had the highest level (95%). By 21 days endothelialisation was complete for all. The everolimus-eluting Element stent had a 1-week delay in luminal endothelialisation but was >89% by 21 days; strut endothelial coverage was >79% in 80% (4/5) of animals, with total strut tissue coverage >95%. Conclusions: This study demonstrated that strut thickness affects strut tissue coverage post stent implantation and the addition of an everolimus-eluting polymer introduces a short delay in endothelialisation. The results highlight the need to control for aspects of stent design such as strut thickness when comparing across drug-eluting stent platforms.