Healing Response to Everolimus-eluting Stent Implantation; Serial Assessment With opticaL Coherence Tomography

Late and very late stent thrombosis is current main issue after introduction of drug-eluting stents .Possible causes of these stent thromboses include thrombus formation resulting from delayed neointimal coverage, spasms occurring at the distal end of the stent implantation site, positive remodeling of coronary arteries caused by local immune reaction to paclitaxel or rapamycin, and vascular endothelial damage induced by the polymer. For BMS, neointimal coverage begins within the first one month after stent implantation and almost completes in three months. For DES, sirolimus eluting stents (SES) for example, neointimal coverage is markedly delayed after stent implantation and the exposed stent struts may be largely attributable to the occurrence of late stent thrombosis. On the other hand, everolimus eluting stents (EES), which have a thinner stent strut layer and improved polymer biocompatibility, it has been reported that earlier and more normal neointimal coverage can be achieved compared with other first-generation DESs, SES and paclitaxel eluting stents (PES). These findings suggest that coverage with vascular endothelium differs among different DES platforms. Optical coherence tomography (OCT) has a resolution of 15 to 20 μm, which is approximately 10 times higher than that of intravascular ultrasound (IVUS). It is therefore necessary to use OCT to accurately evaluate cross-sectional images of the stent struts covered with vascular endothelium. However, no studies have reported the results of continuous observation and evaluation of EES covered with endothelium. Therefore, the investigators investigate time course of neointimal coverage of EES through detailed evaluation by OCT of neointimal coverage at 3, 6, and 12 months after stent implantation.