Coronary Stent Materials and Coatings: A Technology and Performance Update

Abstract

This paper reviews the current state of the art for coronary stent materials and surface coatings, with an emphasis on new technologies that followed on from first-generation bare metal and drug-eluting stents. These developments have been driven mainly by the need to improve long term outcomes, including late stent thrombosis. Biodegradable drug-eluting coatings aim to address the long term effects of residual durable polymer after drug elution; the SYNERGY, BioMatrix, and Nobori stents are all promising devices in this category, with minimal polymer through the use of abluminal coatings. Textured stent surfaces have been used to attached drug directly, without polymer; the Yukon Choice and BioFreedom stents have some promising data in this category, while a hydroxyapatite textured surface has had less success. The use of drug-filled reservoirs looked promising initially but the NEVO device has experienced both technical and commercial set-backs. However this approach may eventually make it to market if trials with the Drug-Filled Stent prove to be successful. Non-pharmacological coatings such as silicon carbide, carbon, and titanium-nitride-oxide are also proving to have potential to provide better performance than BMS, without some of the longer term issues associated with DES. In terms of biological coatings, the Genous stent which promotes attachment of endothelial progenitor cells has made good progress while gene-eluting stents still have some practical challenges to overcome. Perhaps the most advancement has been in the field of biodegradable stents. The BVS PLLA device is now seeing increasing clinical use in many complex indications while magnesium stents continue to make steady advancements.

Evaluation of Early Healing Profile and Neointimal Transformation Over 24 Months Using Longitudinal Sequential Optical Coherence Tomography Assessments and 3-Year Clinical Results of the New Dual-Therapy Endothelial Progenitor Cell Capturing Sirolimus-Eluting Combo Stent

“…[20][21][22] Newer DES with various technologies are being developed. 23,24 A structured systematic evaluation protocol for a DES from early healing to late neointimal transformation, potentially predicting long-term outcomes, has never been described partly because of the lack of high resolution in vivo imaging technology until the availability of frequency-domain OCT. 15,16 We attempted to bridge this scientific gap by first designing and testing the concept of using a novel imaging protocol (longitudinal sequential OCT assessments) to evaluate a new stent platform claimed to be prohealing with a dual-therapy approach, the Combo stent, hoping that such a protocol could help predict outcomes earlier for any new stent platforms, rather than having to wait many years for the positive or adverse results to surface.…”

Stent thrombosis rates the first year and beyond with new- and old-generation drug-eluting stents compared to bare metal stents

“…It is generally accepted that late ST is associated with inadequate stent endothelialization [10]. Whilst the exact cause of poor endothelialization has not been completely elucidated, there are theories that challenge the role of coating polymers due to their potential of evoking localized inflammatory responses [11].…”

Effects of material thickness and processing method on poly(lactic-co-glycolic acid) degradation and mechanical performance

“…Biodegradable polymers such as PLGA have been used in a wide range of biomedical applications [3,4]. Degradation of PLGA is due to the hydrolytic reaction which causes cleavage of the ester bonds of the polymer chains.…”