Coronary Stents

Abstract

Coronary stent technology is a crucial part of most interventional procedures for percutaneous revascularization. Previously, vessel wall injury and plaque fracture were the usual sequelae in response to the mechanical effect of balloon angioplasty. Nowadays, a sophisticated engineering tool serves not only as a scaffolding platform but also as an advanced vector for local anti-proliferative drug delivery to the arterial wall. The wide acceptance of coronary stenting is based on the results of pioneering trials, such as the BENESTENT and STRESS trials, which showed the superiority of stenting over balloon angioplasty in terms of a reduction of angiographic restenosis and the need for repeated intervention. Since then, the growing use of stents in ever more complex lesions and patients has stimulated the introduction of a rapidly increasing number of different stent designs. These have been proposed in order to address physiologic concerns: indeed, a primary aim of stent development is to reduce device profiles and increase flexibility thus facilitating safe delivery of the stent. Percutaneous coronary stent implantation frequently results in significant three-dimensional (3D) changes in the geometry of native coronary arteries. These changes may increase the risk of in-stent re-stenosis due to altered vessel wall compliance and subsequent alterations in shear stress. Additionally, the implantation of a stiff stent within the coronary arteries may result in flexion or hinge points due to the abrupt changes in vessel wall rigidity at the ends of the stent. These hinge points have been associated with increased rates of re-stenosis and may increase the risk of edge dissection and the need for additional stent implantation. Other important issues are lesion coverage, to avoid plaque prolapse, and radial support, to prevent elastic recoil of the artery. Furthermore, the ability to easily access arterial side branches through the struts of a deployed stent in bifurcation lesions has progressively gained importance. Finally, radiologic visibility during angiography is another important element in optimizing the clinical benefits of a stent, especially during placement, while the attenuation index must be considered if, for example, computed tomography will be performed after the procedure.