Drug Eluting Stent Implantation for High Risk Patients and Novel Technologies in Percutaneous Coronary Intervention

Percutaneous coronary intervention is a major treatment strategy for patients with coronary artery disease, and currently coronary stents are widely used in the world.1 Although stent implantation itself has shown to reduce restenosis by preventing both early elastic recoil and late vascular remodeling compared to balloon angioplasty, in-stent restenosis (ISR) still occurs in 10-40% of patients and has been the ‘Achilles’ heel’ of coronary interventions, frequently resulting in repeated revascularization.2,3 Restenosis after coronary stenting occurs secondary to the accumulation of smooth muscle cells and extracellular matrix proteoglycans.4 Despite the sophistication of the new techniques and enormous advance in devices, ISR requiring repeat procedure has been considered as a main limitation of coronary stenting. The advent of drug eluting stents (DES), which consist of a drug (immunosuppressive or antiproliferative drug), a polymer and a metallic platform, has revolutionized the practice of interventional cardiology by significantly reducing the rates of restenosis and repeat revascularization as compared to bare metal stents.5 After the first approval of DES, a large number of patients with coronary artery disease have undergone percutaneous revascularization with DES. However, many trials conducted in the ‘real world’ showed that the problem of restenosis was not completely resolved and still persists. Effect of DES for patients at high risk for ISR, such as acute myocardial infarction, small coronary vessels, aorto-ostial lesions, or lesions of chronic total occlusion (Part 1 of this thesis), have not been fully investigated. In addition, certain potential safety concerns regarding the widespread use of DES have arisen. The most notable drawback of DES is that they could increase the risk of thrombotic complication, especially late stent thrombosis6, although its incidence is low.7 The increased risk of thrombosis with DES utilization may be associated with altered endothelial function8 and/or delayed vascular healing9 induced by cytotoxic and cytostatic drug use. Localized hypersensitivity reactions to the polymer coating of DES and drug itself may also contribute to stent thrombosis.10 To retain the positive clinical aspects of DES and overcome their drawbacks, new concept stents have been developed (Part 2 of this thesis).