RESUMO
Although originally the practice of using balloon catheters proved successful in the short term, the long-term prognosis was less promising because of restenosis, which occurred in >or=30% of patients. This prompted the development of new techniques and mechanical adjuncts, or stents, to maintain lumen patency after balloon angioplasty. Bare metal stents (BMS), the first type of stent used in percutaneous coronary intervention, were designed to address the issues met by balloon angioplasty. BMS reduced the angiographic and clinical restenosis rates in de novo lesions compared to percutaneous transluminal coronary angioplasty alone and decreased the need for emergency coronary artery bypass graft surgery. BMS substantially reduced the incidence of abrupt artery closure, but restenosis still occurred after 6 months in about 20% of cases, necessitating repeat procedures. Drug-eluting stents (DES) improved on the principle of BMS by also delivering drugs locally to inhibit neointimal hyperplasia. DES greatly reduced the incidence of restenosis and resulted in a better safety profile as compared to radiation or systemic drug administration. These advantages and a lower cost compared to surgical interventions make DES an attractive option to treat coronary artery disease. Currently, five DES are available in the USA: the CYPHER sirolimus-eluting stent from Cordis (approved by FDA on 24 April 2003), the TAXUS Express(2) and Liberté paclitaxel-eluting stents from Boston Scientific (approved by FDA on 4 March 2004 and 10 October 2008, respectively) (hereafter TAXUS Express is referred to as TAXUS), the ENDEAVOR zotarolimus-eluting stent from Medtronic (approved by FDA on 1 February 2008), and the XIENCE V everolimus-eluting stent from Abbott Vascular (approved by FDA on 2 July 2008). Following the approval of CYPHER and TAXUS, the clinical data suggested a potential small increase in the rate of stent thrombosis (ST) in DES compared with BMS after implantation. To determine the differences in ST and other rare events between different stents, some modifications have been made to DES clinical trial design, and postmarket surveillance programs have been included to further evaluate the safety and efficacy of each DES. In this review, we will discuss the key clinical outcomes of DES clinical trials, design and key features of the current coronary stents, and major clinical development programs. Postmarket trials, designed to establish long-term safety around ST and other rare clinical events, are also discussed. The future of DES design technologies will also be outlined.
