Coronary stenting: Difference between revisions

[[Improvements in stent plaforms:]] Stent platforms are the metal backbones of the DES. First-generation DES were designed as a standard BMS coated with a polymer and drug. The stent designs of current-generation DES are mainly different from their first-generation predecessors because of a thinner strut thickness. An overview of strut thicknesses of first-generation and current-generation DES is shown in table 1. Another advancement in stent platform design is the use of novel metallic alloys such as cobalt-chromium and platinum-chromium rather than stainless steel. These alloys allow for thinner struts with equal radiopacity and radial support. <br />

[[Improvements in polymer design:]] Improvements in polymer design were again aimed at minimizing the thickness of the polymer. This can be achieved by decreasing the thickness of the polymer itself, or by only coating the abluminal side of the stent with the polymer. Moreover, as the polymers of first-generation DES were thought to be responsible for the increased rates of very late stent thrombosis, an effort was made to create bio-inert and biocompatible polymers e.g. the fluoropolymer (not unlike a Teflon layer in an anti-sticking pan) used in the XIENCE everolimus-eluting stent. Other stent types employ a bioresorbable polymer which is broken down over a period of several months, essentially leaving a BMS behind. However, the benefits of a bioresorbable polymer seem to be limited as shown by a large network meta-analysis involving 63,242 patients showing that durable polymer everolimus-eluting stents (such as XIENCE and PROMUS) and zotarolimus-eluting stents (such as RESOLUTE) had a superior safety profile compared with biolimus-eluting bioresorbable DES.(15) Yet another type of stent (BIOFREEDOM) uses no polymer at all, but elutes a drug from small reservoirs on its abluminal surface. This stent has shown superior outcomes in terms of repeat revascularization when compared to a similar BMS, but has not been compared against other DES types in a randomized controlled trial.(16)<br />

[[Improvements in antirestenotic drugs:]] Improvements in antirestenotic drugs have been relatively modest compared with the aforementioned improvements in stent platforms and polymers. Experiences with first-generation DES led the interventional cardiology community to conclude that sirolimus and its analogues were superior to paclitaxel for use on a DES. The cytotoxic properties of paclitaxel are probably too aggressive for the purpose of preventing formation of neointima, the more subtle anti-inflammatory and cytostatic effects of sirolimus seem to be better suited for this purpose. Several analogues of sirolimus have been developed, these are chemically altered forms of the drug with improved lipophilicity such as biolimus A9 or zotarolimus.  <br />