Chapter 30: Drug-Eluting Coronary Stents

INTRODUCTION

Several major leaps in technology and immense research and development have led to the current wide use of drug-eluting stents (DES). Stents were initially developed to reduce the high rates of restenosis and acute vessel closure following balloon angioplasty–induced endothelial cell denudation and coronary artery medial layer tearing.¹ The first bare metal stent (BMS) implantation in a coronary artery was reported by Sigwart et al² in 1987, and the first randomized trial comparing balloon angioplasty and BMS was reported by Fischman et al³ in 1994. As compared to balloon angioplasty, BMS implantation was associated with an improved rate of procedural success, a lower rate of angiographically detected restenosis, similar rates of clinical events after 6 months, and a less frequent need for target vessel revascularization (TVR).³ These results eventually led to the use of BMS as the standard of care for the treatment of de novo coronary stenosis. The use of BMS, however, was associated with a high incidence of in-stent restenosis (ISR) mainly due to intimal hyperplasia.⁴ The high ISR rates in BMS eventually led to the idea of coating the BMS with antiproliferative agents. Therefore, the primary purpose of DES has been the prevention of vessel recoil, negative remodeling, and ISR. First introduced in 2002, first-generation DES have been shown to be superior to BMS with respect to lower rates of clinical and angiographic restenosis and target lesion revascularizations (TLR) as compared to BMS.^5,6 However, following real-world experience, concerns regarding high rates of late stent thrombosis (ST) have emerged,⁷ leading to a change in the recommendations for dual antiplatelet therapy following DES implantation.⁸ The vast research and development leading to a newer generations of DES, better understanding of the mechanisms of ST, and advances in technology, technique, adjunctive pharmacology, and operator experience have resulted in improved outcomes and the widespread use of DES. This eventually lead to the fact that the vast majority of stents being implanted during percutaneous coronary intervention (PCI) in the United States are DES⁹ as well as to the wide endorsement for the use of these stents in US and European clinical guidelines.^10,11

DRUG-ELUTING STENT STRUCTURE

The basic structure of DES includes a metallic strut platform, a polymer, and the drug. Due to the concept of persistent arterial wall inflammation attributed to the polymer and the risk for ST, novel DES designs have been introduced and include the biodegradable polymer and polymer-free DES,¹² discussed later, and the bioresorbable vascular scaffold systems.¹³ A design summary for the first- and second-generation DES available in the United States for clinical use as well as newer platforms with bioresorbable polymer and polymer-free DES are presented in Table 30-1 and Figures 30-1 and 30-2.