4 - Polymer-free drug-eluting stents

Abstract

Drug-eluting stents (DES) have revolutionized the way that advanced coronary heart disease is now treated. These devices are associated with much lower rates of restenosis than their bare metal stent counterparts. However, the presence of a polymer coating on the stent surface, which allows for incorporation and sustained release of drug into the artery, has been implicated in the occurrence of late stent thrombosis. Consequently, a great many different polymer-free DES have since been developed. Early approaches involving direct loading of the drug on to unmodified stent surfaces were largely ineffective, which was likely due to suboptimal drug delivery kinetics characterized by very rapid release. It has since been found that stent surface modification strategies at the macro, micro and nanoscale can be used to provide more sustained drug release, with some of these strategies producing clinical results that are comparable to polymer-coated DES. Emerging clinical data on the use of the Cre8, BioFreedom, and the latest Drug Filled Stent from Medtronic Inc. suggest that these particular polymer-free DES may inhibit restenosis without delaying recovery of the endothelium, which would represent a step change improvement in performance. Whilst these devices would therefore appear to be particularly beneficial in treating high bleeding risk patients, the reduction in antiplatelet therapy duration required is likely to be an appealing feature that may see them make a wider impact more generally.