Vulnerable struts with CRE8, Biomatrix and Xience stents assessed with OCT and their correlation with clinical variables at 6-month follow-up: the CREBX-OCT study

Nanotechnology in development of next generation of stent and related medical devices: Current and future aspects

Coronary stents have saved millions of lives in the last three decades by treating atherosclerosis especially, by preventing plaque protrusion and subsequent aneurysms. They attenuate the vascular SMC proliferation and promote reconstruction of the endothelial bed to ensure superior revascularization. With the evolution of modern stent types, nanotechnology has become an integral part of stent technology. Nanocoating and nanosurface fabrication on metallic and polymeric stents have improved their drug loading capacity as well as other mechanical, physico-chemical, and biological properties. Nanofeatures can mimic the natural nanofeatures of vascular tissue and control drug-delivery. This review will highlight the role of nanotechnology in addressing the challenges of coronary stents and the recent advancements in the field of related medical devices. Different generations of stents carrying nanoparticle-based formulations like liposomes, lipid-polymer hybrid NPs, polymeric micelles, and dendrimers are discussed highlighting their roles in local drug delivery and anti-restenotic properties. Drug nanoparticles like Paclitaxel embedded in metal stents are discussed as a feature of first-generation drug-eluting stents. Customized precision stents ensure safe delivery of nanoparticle-mediated genes or concerted transfer of gene, drug, and/or bioactive molecules like antibodies, gene mimics via nanofabricated stents. Nanotechnology can aid such therapies for drug delivery successfully due to its easy scale-up possibilities. However, limitations of this technology such as their potential cytotoxic effects associated with nanoparticle delivery that can trigger hypersensitivity reactions have also been discussed in this review. This article is categorized under: Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Therapeutic Approaches and Drug Discovery > Nanomedicine for Cardiovascular Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Computational simulation of stent thrombosis induced by various degrees of stent malapposition

Percutaneous coronary intervention with stent implantation is one of the most commonly used approaches to treat coronary artery stenosis. Stent malapposition (SM) can increase the incidence of stent thrombosis, but the quantitative association between SM distance and stent thrombosis is poorly clarified. The objective of this study is to determine the biomechanical reaction mechanisms underlying stent thrombosis induced by SM and to quantify the effect of different SM severity grades on thrombosis. The thrombus simulation was performed in a continuous model based on the diffusion-convection response of blood substance transport. Simulated models included well-apposed stents and malapposed stents with various severities where the detachment distances ranged from 0 to 400 μm. The abnormal shear stress induced by SM was considered a critical contributor affecting stent thrombosis, which was dependent on changing SM distances in the simulation. The results illustrate that the proportion of thrombus volume was 1.88% at a SM distance of 75 μm (mild), 3.46% at 150 μm, and 3.93% at 400 μm (severe), but that a slight drop (3.18%) appeared at the detachment distance of 225 μm (intermediate). The results indicate that when the SM distance was less than 150 μm, the thrombus rose notably as the gap distance increased, whereas the progression of thrombogenicity weakened when it exceeded 150 μm. Therefore, more attention should be paid when SM is present at a gap distance of 150 μm. Moreover, when the SM length of stents are the same, thrombus tends to accumulate downstream towards the distal end of the stent as the SM distance increases.

Malapposed Struts with Cre8, Biomatrix, and Xience Stents Assessed with OCT Immediately after Implantation and at 6-Month Follow-Up: Can the Different Biomechanical Characteristics of the Three Stents Impact on Struts Malapposition?

Background. Although the clinical effects of stent malapposition remain controversial, several analyses of stent registries consistently have found that malapposed struts were frequently identified in patients who experienced stent thrombosis. In this study, which is a subanalysis of the previously published CREBX-OCT study, we compared optical coherence tomography (OCT) analysis at the index percutaneous coronary intervention (PCI) and at six-month follow-up in 37 patients randomly assigned to receive, by a single operator, three different second-generation drug-eluting stents (Cre8, Biomatrix, and Xience) aiming to clarify if the malapposition observed at six-month follow-up was persistent or late-acquired. Moreover, we investigated if there were some differences in the behavior of the three different kinds of stents in relation to the struts malapposition. Material and Methods. We analyzed 614 and 599 cross sections and 5514 and 5377 struts at the index PCI and at six-month follow-up, respectively. The qualitative analysis of the plaque composition among the three groups did not show significant differences. Results. The lumen area did not significantly change from the index procedure to the six-month follow-up in the three groups; on the contrary, the number of malapposed struts increased significantly in the Cre8 and Biomatrix groups but not in the Xience group: 0.58 ± 1.51 and 3.29 ± 5.33 ( $p<0.023$ ) in the Cre8 group, 0.55 ± 1.81 and 1.73 ± 2.28 ( $p<0.024$ ) in the Biomatrix group, and 0.55 ± 1.5 and 0.25 ± 0.87 ( $p<0.166$ ) in the Xience group, respectively. Conclusions. Therefore, the malapposition observed at six-month follow-up in our study population could be mainly considered as acquired and attributable to biomechanical reasons due to the structural differences among the three stents. This trial is registered with Clinical Trials.gov Identifier: NCT02850497.

The Cre8 amphilimus-eluting stent for the treatment of coronary artery disease: safety and efficacy profile

Introduction: Polymer-free drug-eluting stents are designed with stent surface modifications and drug-matrix formulations in order to release antiproliferative agents without the need of a polymer coating. Polymer-free technologies have the potential to overcome complications due to polymer persistence over time, such as local inflammatory reactions, delayed arterial healing, neoatherosclerosis, and subsequent ischemic adverse events.Areas covered: The Cre8 polymer-free amphilimus-eluting stent received CE mark in 2011 and was conceived with the aim of addressing the safety and efficacy limitations of early generation drug-eluting stents based on permanent polymer coatings. Besides the absence of polymer, the main features of the Cre8 stent include the abluminal reservoirs, the passive carbon film coating, and the antiproliferative agent formulation based on sirolimus mixed with free-fatty acid chain - namely amphilimus. This review will focus on the Cre8 development, technical characteristics, preclinical evidence, clinical efficacy and safety, and future perspectives.Expert opinion: The Cre8 stent has shown favorable angiographic and clinical outcomes at short and medium-term follow-up. This technology might provide a benefit in patients with diabetes. Further randomized evidence is required to provide an adequate clinical evaluation of this promising technology in patients with and without diabetes.