Long Term Follow-up after Drug-eluting Stent Implantation and Early Experience with Endothelial Progenitor Cell Capture Stent

Intracoronary stent replacement is being used increasingly for the treatment of atherosclerotic coronary artery disease and has gained widespread acceptance. Although stent implantation itself has been shown to reduce restenosis compared to balloon angioplasty, in-stent restenosis still occurs in 10-40% of patients. In-stent restenosis has long been considered the main limitation hampering the long-term efficacy of coronary stenting. Restenosis after stent occurs secondary to the accumulation of smooth muscle cells and extracellular matrix which consists of proteoglycans, hyaluronan and collagen. To overcome this major limitation, drug-eluting stents were developed. Drug-eluting stents consist of a drug (immunosuppressive, antiproliferative, or anti-inflammatory drug), a polymer, and a stent platform. Several drugs with durable or erodable polymers were tested in clinical trials and showed that drug-eluting stents significantly inhibit neointimal growth compared with bare metal stents. Currently, drug-eluting stents have been widely distributed all over the world and become main-stream of percutaneous coronary intervention. However, (1) long-term efficacy and chronic vascular response after drug-eluting stents implantation in humans (Part 1 of this thesis) (2) effect of drugeluting stents for patients with high in-stent resteonsis risk factors, such as diffuse lesion, diabetes mellitus, left main coronary artery lesion, chronic total occlusion or bifurcation lesion (Part 2 of this thesis), have not been fully investigated. Furthermore, problem of stent thrombosis is still observed in drug-eluting stent era. Drug-eluting stents interferes with the natural healing response by preventing or significantly delaying the formation of a functional endothelial lining over stent. The early establishment of a functional endothelial layer after stent implantation may resolve this issue. Recently, the existence of circulating endothelial progenitor cells has been identified as a key factor for re-endothelialization. 8,9 New concept stent using immobilized antibodies targeted at endothelial progenitor cell surface antigens has been developed. (Part 3 of this thesis).