Are Drug-eluting Stents the Future of Coronary Artery Treatment for All Patient Types?

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Abstract

Introduction
Coronary artery bypass grafting (CABG) was introduced in 1968 and rapidly became the gold standard treatment for patients with coronary artery disease (CAD). Percutaneous coronary intervention (PCI) was introduced into clinical practice almost 10 years later in 1977 and was only initially considered appropriate for patients with single-vessel disease. However, as experience and technology have advanced, PCI procedures have been expanded to treat patients with multi-vessel disease. Evolution in percutaneous revascularisation includes the introduction of stents and although the use of bare metal stents (BMS) has reduced the incidence of restenosis compared with balloon angioplasty, it still remains an important limitation.

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Since publication of the Randomized Study with the Sirolimus-Eluting Bx Velocity Balloon-Expandable Stent (RAVEL) using drug-eluting stents (DES), other studies have shown DES to dramatically reduce the incidence of restenosis and repeat revascularisation in single vessel de novo disease. However, studies directly comparing treatment options have been limited to highly selected patient populations. The optimal treatment strategy remains undetermined for patients presenting with more severe forms of CAD involving all three coronary arteries, the left main artery or both. Factors influencing patient stratification include left main CAD, diabetes mellitus, local expertise and patient preference. Technical feasibility also influences the decision to proceed with CABG surgery. The recently published PCI guidelines by the European Society for Cardiology (ESC) recommend the overall use of PCI in stable CAD and early PCI in patients with non-ST-segment elevation (NSTE) and nonseratonin elevation myocardial infarction (NSTEMI) (except those with diabetes and multi-vessel disease) but suggest that these exclusions might have to be revised with the use of DES.

CABG
Recent advances in coronary surgery include improvements in pre-operative risk assessment and management, anaesthesia, the use of arterial grafts, the introduction of mini-invasive surgery, off-pump surgery and improvement in post-operative care.

These advances have resulted in further improvements with reduced hospital morbidity and mortality. Furthermore, with the use of arterial grafts the patency rate of bypass graft has been increased (left and right internal mammary artery showing patency rates of more than 90% and ~80%).

BMS
The introduction of BMS, improved delivery systems, experience of the operators and the identification of risk factors and high-risk lesions (with prognostic implication for short- and long-term outcomes) have shown short-term improvements in procedural outcomes and reduction in restenosis rates. One-year follow-up data of the Belgian Netherlands stent (BENESTENT) trial also showed no significant differences in coronary events or death between the stent and balloon angioplasty groups. However, the requirement for a repeat angioplasty procedure (at five years) was significantly lower in the stent group (17%) than the balloon angioplasty group (27.3%, relative risk (RR) 0.63, 95% confidence interval (CI) 0.45 to 0.88, P=0.008).

In selected patients, the use of BMS can result in an improved rate of procedural success, a lower rate of restenosis, a less frequent need for repeat intervention and improved outcomes of patients for up to one year. Despite the benefits of BMS, restenosis and target vessel revascularisation still occur due to eventual neointimal hyperplasia. BMS therefore have limited use when applied to the treatment of multi-vessel disease.

DES
The use of DES has further reduced the incidence of restenosis and repeat revascularisation in single vessel de novo disease. These stents have bioactive coatings (polymer or non-polymer) that allow the release (through a complex mechanism) of various antiinflammatory and anti-proliferative drugs at high concentrations in the wall of the treated vessel without significant release into the bloodstream, to prevent restenosis of the vessel.

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