The Development of Coronary Artery Stents: From Bare-Metal to Bio-Resorbable Types

Abstract

Abstract:Coronary artery disease is the leading cause of death worldwide. Conventional balloon angioplasty is associated with high rates of complications such as coronary dissection and vessel recoil. The deployment of bare-metal stents (BMSs) can overcome these problems and achieve a better patency rate than simple balloon angioplasty. It has been shown that the stent design including structure platform, size, length, and strut thickness has a major influence on the clinical results. Even though angioplasty with BMS implantation is widely used in coronary interventions, the restenosis rate due to neointimal hyperplasia remains high. Therefore, drug-eluting stents (DESs) coated with anti-proliferative agents and polymers have been developed to reduce the restenosis rate and improve the clinical outcomes. Although the repeat revascularization rate of DESs is lower than that of BMSs, the long-term stent thrombosis rate is higher than for BMSs. Therefore, new and emerging generations of stents, in which, for example, thinner struts and bioresorbable polymers are used, are available for clinical use. However, there are only a limited number of clinical trials, in which these newer stents have been compared with BMSs and first-and second-generation DESs. The purpose of this review was to provide up-to-date information on the evolution of coronary artery stents from BMSs to DESs to bioresorbable stents (BRSs).Keywords: coronary artery disease; stent; bioresorbable; drug; polymer; strut The Evolution of Coronary Stent DevelopmentCoronary artery disease (CAD) is a major cause of mortality and morbidity. One of the treatment options for CAD is a percutaneous coronary intervention. Balloon angioplasty alone, which involves pushing the plaque to the walls of the artery, can achieve a larger luminal diameter in the acute phase. However, arterial recoil, dissection, and late neointimal hyperplasia can result in vessel restenosis. Therefore, bare metal stents (BMSs) made from metallic materials were developed to overcome the dissection and the restenosis complications caused by recoil. Although the restenosis rate can be reduced by stenting, the in-stent restenosis (ISR) rate is still high at around 20%-30% [1,2]. ISR is mostly caused by neointimal hyperplasia.A reduction in restenosis was first achieved with the evolution of the stent platform, including thinner stent struts and new metal compounds. Furthermore, new drug delivery systems and polymer coatings have been developed to achieve better clinical outcomes. The first generation of drug-eluting stents (DESs) with a sirolimus or paclitaxel coating showed better clinical outcomes with lower rates of cardiac death, myocardial infarction, and target vessel revascularization than BMSs [3,4]. However, increased rates of stent thrombosis were reported with first-generation

Recent Advances in Manufacturing Innovative Stents

“…The idea of stent bioresorbability is perceived as revolutionary (stents of third generation) according to Erne et al [100] and attracted a strong interest of both engineers and clinicians. Multiple published reviews focus on clinical, material, and technological aspects of bioresorbable stents [5,54,[101][102][103][104]. Figure 2a schematically presents the behavior of non-resorbable and resorbable stent after implantation.…”

“…Considering that restenosis rates in polymer stents are similar to that of BMS, the latter has the advantage. Ho et al [102] provides contemporary data on the evolution of coronary artery stents from BMS through drug-eluting stents to bioresorbable stents. Their manuscript highlights that BMS are suitable for the cardiovascular application and are strongly dependent on the structure platform, size, length, and strut thickness.…”

“…The development of newer stents, with thinner struts and covered with bioresorbable polymers can present an important improvement, especially because of the reduction of the restenosis rate. From an evolutionary point of view, the first reduction of the restenosis rate was achieved by using thinner struts and new metal compounds, later by using drug-eluting stents and polymer coated stents [32][33][34]102].…”

Reduction in the Corrosion Rate of Magnesium and Magnesium Alloy Specimens and Implications for Plain Fully Bioresorbable Coronary Artery Stents: A Review

“…There are three reasons for including this section. The first was to present a compact but comprehensive summary of all the theoretical advantages and shortcomings of all the various types of stents, since this kind of summary is very scare in the literature [32]. The second was to highlight the motivation for introduction of a FBRS and to compare and contrast it vis a visa durable stent.…”

“…Stent types have evolved from bare metal stents (introduced in 1987) through durable polymer-coated drug-eluting stents (introduced in 2004) to plain or coated fully bioresorbable stents (FBRSs) (introduced in 2010) (Figure 2) [32]. In a plain FBRS, the scaffold is made of Mg or a Mg alloy, whereas, in a coated FBRS, the scaffold, made of either a Mg alloy or a bioresorbable polymer, is coated with a bioresorbable polymer in which an anti-proliferative drug is embedded.…”