Although most currently approved stents are made of 316 L stainless steel, 15 other materials have been used, such as cobalt chromium in the Multi-Link Vision™ stent, which is more radiopaque and elicits a less vigorous host response than stainless steel (Guidant pamphlet. Radiopaque gold markers are occasionally added to stents for the sole purpose of improving visualisation, helping to localise the stent during deployment at the target lesion.
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14 Although stent flexibility and trackability are highly dependent on mechanical stent design, radiological visibility and host biocompatibility rely on stent material. Ultimately, stent design should optimise flexibility, trackability, visibility, and biocompatibility (table 2 2 ).
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11, 12 Previous studies have shown that differences in stent design can have a profound influence on late lumen loss 13 and neointima proliferation, 14 thereby affecting restenosis rates and requirements for post-procedural intervention. Stent design affects many properties of the stent, such as elastic recoil and rigidity-two undesirable stent characteristics. Furthermore, such designs may have differences in strut pattern and width or overall stent diameter, to name just a few variations. Any number of stent designs can be created within a coil, tubular mesh, or slotted tube framework. Finally, slotted tube stents are made from tubes of metal from which a stent design is laser cut. In contrast, tubular mesh stents consist of wires wound together in a meshwork, forming a tube. 9 Coil stents are characterised by metallic wires or strips formed into a circular coil shape. On the basis of design, stents can be divided into three groups: coil, tubular mesh, and slotted tube. Although a wide array of stent designs and technologies has been introduced into the burgeoning stent market, most coronary stents can still be classified on the basis of: (1) nature of expansion or (2) stent design (table 1 1 ). Worldwide, $2.5 billion was spent on stents in 2003, and this value is expected to increase to $4.0 billion in 2004. 8 The FDA has currently approved at least 16 models of stents from nine different manufacturers. 6, 7 Thus, PTCA with stenting has now become the preferred treatment of CAD for interventional cardiologists. 4 By 1994, the Food and Drug Administration (FDA) had approved two stents (Gianturco-Roubin stent and the Palmaz-Schatz™ stent), 5 and additional studies by Serruys et al and Fischman et al confirmed that stenting led to improved clinical outcome over PTCA alone. 3 Sigwart et al first reported the efficacy of stents in reducing restenosis rates in 1987. 2 Coronary artery stents were developed to provide a metal scaffolding for the angioplastied vessel, in an attempt to limit negative remodelling. Restenosis is characterised by neointima formation resulting from the migration of proliferating medial vascular smooth muscle cells to the intima, and the synthesis of matrix components, particularly collagen, with resultant stenosis and constrictive remodelling. “Percutaneous transluminal coronary angioplasty with stenting has now become the preferred treatment of coronary artery disease for interventional cardiologists” 1 However, the incidence of restenosis of coronary arteries was an important problem, necessitating repeated interventional procedures in 30% of patients treated with PTCA alone.
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Until 1994, the use of percutaneous transluminal coronary angioplasty (PTCA) alone as a treatment for coronary artery disease had been increasing steadily. The introduction of angioplasty for the treatment of coronary artery disease (CAD) led to the development of a completely new approach to CAD.