Coronary stents: looking forward

Topology optimization of coronary artery stent considering structural and hemodynamic parameters

In the present study, the impact of geometric variables and structural features of stents on hemodynamic parameters is investigated. Intravascular stent implantation is a treatment method whose success largely depends on the geometric structure of the stent and its effect on hemodynamic parameters. Medical devices called stents are inserted into arteries to restore blood flow when an artery is blocked. In this research, an optimal stent was designed and its effect compared to the common commercial stent used for coronary arteries was investigated and compared. It has been found that the geometry of the stent has an effective impact on the wall shear stress in the stented artery. Therefore, in this article, the importance of stent structures in the treatment of the coronary artery disease is discussed. For this purpose, first, an optimal stent is created with the topology optimization technique to find the best structure in the stent design. Finally, the optimized stent is numerically verified with ANSYS software and compared with existing commercial stents, and then the prototype is fabricated using additive manufacturing techniques. Commercial software ABAQUS, SolidWorks, and ANSYS are used in this research. The results showed that in optimizing a square plate, a sample with a minimum residual volume limit equal to 10 and 7 % can be selected as the optimal state. The results indicate that the new design can improve the distribution of wall shear stresses to reduce the adverse hemodynamic changes. Therefore, the proposed stent geometric structure can help improve the treatment. Finally, the optimized stent along with a commercial stent was made with the 3D printing method.

The Mechanical and Electrochemical Stability of Trimethysilane Plasma Nanocoatings Deposited onto Cobalt Chromium Cardiovascular Stents

The objective of this study was to evaluate the coating integrity performance and corrosion protection property of trimethylsilane (TMS) plasma nanocoatings that were directly deposited onto cobalt chromium (CoCr) L605 cardiovascular stents. Hydrophilic surfaces were achieved for the TMS plasma nanocoatings that were deposited onto the coronary stents through NH3/O2 (2:1 molar ratio) plasma post-treatment. With a coating thickness of approximately 20-25 nm, the TMS plasma nanocoatings were highly durable and able to resist delamination and cracking from crimping and expansion by a Model CX with a J-Crimp Station. The stent surface that was evaluated by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) showed no indications of pitting, corrosion, or adsorption products on either the luminal or abluminal surfaces of the stents, in contrast to the uncoated stent surface. The TMS plasma nanocoatings significantly enhanced the stent's corrosion resistance in immersion experiments that followed the ASTM F2129-15 corrosion protocol, evident in the increase of the open circuit potential (OCP) from 0.01 V for the uncoated L605 stent to 0.18 V for the plasma-nanocoated L605 stent, reducing potential cytotoxic metal ion release. Cyclic polarization (CP) curves show that the corrosion rate (density level) observed in plasma-nanocoated L605 stents was approximately half an order of magnitude lower than that of the uncoated stents, indicating improved corrosion protection of the stents. CP curves of the TMS plasma-nanocoated stents with different coating thicknesses show that, in the range of 20-65 nm, the coating thickness does not result in any difference in the corrosion resistance of the stents.

Revolutionizing Cardiovascular Frontiers: A Dive Into Cutting-Edge Innovations in Coronary Stent Technology

Plain balloon angioplasty was the initial method used to enlarge the intracoronary lumen size. However, it was linked to acute coronary closure due to early vessel recoil. This led to the invention of coronary stents, which offer mechanical support to open and maintain the vascular lumen. Nevertheless, the metallic scaffold introduced other issues, such as thrombosis and restenosis caused by neointimal proliferation. To address these concerns, polymers were employed to cover the scaffold, acting as drug reservoirs and regulators for controlled drug release. The use of polymers prevents direct contact between blood and metallic scaffolds. Drugs within the stent were incorporated to inhibit proliferation and expedite endothelialization in the healing process. Despite these advancements, adverse effects still arise due to the inflammatory reaction caused by the polymer material. Consequently, resorbable polymers and scaffolds were later discovered, but they have limitations and are not universally applicable. Various scaffold designs, thicknesses, materials, polymer components, and drugs have their own advantages and complications. Each stent generation has been designed to address the shortcomings of the preceding generation, yet new challenges continue to emerge. Conflicting data regarding the long-term safety and efficacy of coronary stents, especially in the extended follow-up, further complicates the assessment.

Endovascular Drug Delivery

Drug-eluting stents (DES) and balloons revolutionize atherosclerosis treatment by targeting hyperplastic tissue responses through effective local drug delivery strategies. This review examines approved and emerging endovascular devices, discussing drug release mechanisms and their impacts on arterial drug distribution. It emphasizes the crucial role of drug delivery in modern cardiovascular care and highlights how device technologies influence vascular behavior based on lesion morphology. The future holds promise for lesion-specific treatments, particularly in the superficial femoral artery, with recent CE-marked devices showing encouraging results. Exciting strategies and new patents focus on local drug delivery to prevent restenosis, shaping the future of interventional outcomes. In summary, as we navigate the ever-evolving landscape of cardiovascular intervention, it becomes increasingly evident that the future lies in tailoring treatments to the specific characteristics of each lesion. By leveraging cutting-edge technologies and harnessing the potential of localized drug delivery, we stand poised to usher in a new era of precision medicine in vascular intervention.

Hybrid interpenetrating network of polyester coronary stent with tunable biodegradation and mechanical properties

Poly(l-lactide) (PLLA) is an important candidate raw material of the next-generation biodegradable stent for percutaneous coronary intervention, yet how to make a polyester stent with sufficient mechanical strength and relatively fast biodegradation gets to be a dilemma. Herein, we put forward a hybrid interpenetrating network (H-IPN) strategy to resolve this dilemma. As such, we synthesize a multi-functional biodegradable macromer of star-like poly(d,l-lactide-co-ɛ-caprolactone) with six acrylate end groups, and photoinitiate it, after mixing with linear PLLA homopolymer, to trigger the free radical polymerization. The resultant crosslinked polymer blend is different from the classic semi-interpenetrating network, and partial chemical crosslinking occurs between the linear polymer and the macromer network. Combined with the tube blow molding and the postprocessing laser cutting, we fabricate a semi-crosslinked-polyester biodegradable coronary stent composed of H-IPN, which includes a physical network of polyester spherulites and a chemical crosslinking network of copolyester macromers and a part of homopolymers. Compared with the currently main-stream PLLA stent in research, this H-IPN stent realizes a higher and more appropriate biodegradation rate while maintaining sufficient radial strength. A series of polymer chemistry, polymer physics, polymer processing, and in vitro and in vivo biological assessments of medical devices have been made to examine the H-IPN material. The interventional implanting of the H-IPN stent into aorta abdominalis of rabbits and the follow-ups to 12 months have confirmed the safety and effectiveness.

Advances in Fabrication Technologies for the Development of Next-Generation Cardiovascular Stents

Coronary artery disease is the most prevalent cardiovascular disease, claiming millions of lives annually around the world. The current treatment includes surgically inserting a tubular construct, called a stent, inside arteries to restore blood flow. However, due to lack of patient-specific design, the commercial products cannot be used with different vessel anatomies. In this review, we have summarized the drawbacks in existing commercial metal stents which face problems of restenosis and inflammatory responses, owing to the development of neointimal hyperplasia. Further, we have highlighted the fabrication of stents using biodegradable polymers, which can circumvent most of the existing limitations. In this regard, we elaborated on the utilization of new fabrication methodologies based on additive manufacturing such as three-dimensional printing to design patient-specific stents. Finally, we have discussed the functionalization of these stent surfaces with suitable bioactive molecules which can prove to enhance their properties in preventing thrombosis and better healing of injured blood vessel lining.

A paradigm for high-throughput screening of cell-selective surfaces coupling orthogonal gradients and machine learning-based cell recognition

The combinational density of immobilized functional molecules on biomaterial surfaces directs cell behaviors. However, limited by the low efficiency of traditional low-throughput experimental methods, investigation and optimization of the combinational density remain daunting challenges. Herein, we report a high-throughput screening set-up to study biomaterial surface functionalization by integrating photo-controlled thiol-ene surface chemistry and machine learning-based label-free cell identification and statistics. Through such a strategy, a specific surface combinational density of polyethylene glycol (PEG) and arginine-glutamic acid-aspartic acid-valine peptide (REDV) leads to high endothelial cell (EC) selectivity against smooth muscle cell (SMC) was identified. The composition was translated as a coating formula to modify medical nickel-titanium alloy surfaces, which was then proved to improve EC competitiveness and induce endothelialization. This work provided a high-throughput method to investigate behaviors of co-cultured cells on biomaterial surfaces modified with combinatorial functional molecules.

Drug-Eluting Stents: Technical and Clinical Progress

Drug-eluting stents (DES) demonstrated superior efficacy when compared to bare metal stents and plain-old balloon angioplasty and are nowadays used in almost all percutaneous revascularization procedures. The design of the stent platforms is constantly improving to maximize its efficacy and safety. Constant development of DES includes adoption of new materials used for scaffold production, new design types, improved overexpansion abilities, new polymers coating and, finally, improved antiproliferative agents. Especially nowadays, with the immense number of available DES platforms, it is crucial to understand how different aspects of stents impact the effect of their implantation, as subtle differences between various stent platforms could impact the most important issue-clinical outcomes. This review discusses the current status of coronary stents and the impact of stent material, strut design and coating techniques on cardiovascular outcomes.

Underutilization of Drug-Eluting Stents in Infrapopliteal Intervention for Chronic Limb-Threatening Ischemia

PURPOSE

Multiple randomized clinical trials have shown superiority of drug-eluting stents (DES) over bare-metal stents (BMS) for infrapopliteal disease. However, real-world data on DES utilization and outcomes in infrapopliteal chronic limb-threatening ischemia (CLTI) patients are unknown.

MATERIALS AND METHODS

We utilized the Nationwide Readmission Database (NRD) from 2016 to 2017 to extract patients undergoing infrapopliteal intervention with stents (BMS and DES) for CLTI using appropriate ICD-10 codes. Multilevel logistic regression with hospital ID as random effect was used to assess DES utilization. Primary outcome was the composite of target limb major amputation (TLmajA) and target limb revascularization (TLR). Multivariate Cox-proportional hazard regression was used to adjust for confounders.

RESULTS

Our study included a total of 1817 patients. Of these patients, 1056 patients (58.1%) received DES; DES utilization was stable (relative change: +2.5%, p-trend: 0.867) between 2016 and 2017 and was higher in teaching hospitals (adjusted odds ratio [aOR] = 1.28, 95% CI = 1.03-1.61, p=0.029] and medium (aOR = 3.13, 95% CI = 2.17-4.55, p≤0.001) and large (aOR = 1.56, 95% CI = 1.14-2.17, p=0.005) bed-sized hospitals. Inter-class correlation was 0.44 suggesting ~44% variation in DES utilization between any 2 random hospitals; DES was associated with lower rate of the primary composite outcome (aHR = 0.75, 95% CI = 0.62-0.92, p=0.004) compared with BMS.

CONCLUSION

In patients undergoing infrapopliteal intervention for CLTI, DES demonstrated significant underutilization despite supportive evidence of their superiority compared with BMS; DES was associated with improvement in the primary composite outcome compared with BMS.

Evaluation of coronary stents: A review of types, materials, processing techniques, design, and problems

In the world, one of the leading causes of death is coronary artery disease (CAD). There are several ways to treat this disease, and stenting is currently the most appropriate way in many cases. Nowadays, the use of stents has rapidly increased, and they have been introduced in various models, with different geometries and materials. To select the most appropriate stent required, it is necessary to have an analysis of the mechanical behavior of various types of stents. The purpose of this article is to provide a complete overview of advanced research in the field of stents and to discuss and conclude important studies on different topics in the field of stents. In this review, we introduce the types of coronary stents, materials, stent processing technique, stent design, classification of stents based on the mechanism of expansion, and problems and complications of stents. In this article, by reviewing the biomechanical studies conducted in this field and collecting and classifying their results, a useful set of information has been presented to continue research in the direction of designing and manufacturing more efficient stents, although the clinical-engineering field still needs to continue research to optimize the design and construction. The optimum design of stents in the future is possible by simulation and using numerical methods and adequate knowledge of stent and artery biomechanics.

Advances in the development of biodegradable coronary stents: A translational perspective

Implantation of cardiovascular stents is an important therapeutic method to treat coronary artery diseases. Bare-metal and drug-eluting stents show promising clinical outcomes, however, their permanent presence may create complications. In recent years, numerous preclinical and clinical trials have evaluated the properties of bioresorbable stents, including polymer and magnesium-based stents. Three-dimensional (3D) printed-shape-memory polymeric materials enable the self-deployment of stents and provide a novel approach for individualized treatment. Novel bioresorbable metallic stents such as iron- and zinc-based stents have also been investigated and refined. However, the development of novel bioresorbable stents accompanied by clinical translation remains time-consuming and challenging. This review comprehensively summarizes the development of bioresorbable stents based on their preclinical/clinical trials and highlights translational research as well as novel technologies for stents (e.g., bioresorbable electronic stents integrated with biosensors). These findings are expected to inspire the design of novel stents and optimization approaches to improve the efficacy of treatments for cardiovascular diseases.

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Bioresorbable stents can overcome the limitations of non-degradable stents.

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3D printing of shape-memory polymeric stents can lead to better clinical outcomes.

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Advances in Mg-, Fe- and Zn-based stents from a translational perspective.

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Electronic stents integrated with biosensors can covey stent status in real time.

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Development in the assessment of stent performance in vivo.

Design and Verification of a Novel Perfusion Bioreactor to Evaluate the Performance of a Self-Expanding Stent for Peripheral Artery Applications

Endovascular stenting presents a promising approach to treat peripheral artery stenosis. However, a significant proportion of patients require secondary interventions due to complications such as in-stent restenosis and late stent thrombosis. Clinical failure of stents is not only attributed to patient factors but also on endothelial cell (EC) injury response, stent deployment techniques, and stent design. Three-dimensional in vitro bioreactor systems provide a valuable testbed for endovascular device assessment in a controlled environment replicating hemodynamic flow conditions found in vivo. To date, very few studies have verified the design of bioreactors based on applied flow conditions and their impact on wall shear stress, which plays a key role in the development of vascular pathologies. In this study, we develop a computationally informed bioreactor capable of capturing responses of human umbilical vein endothelial cells seeded on silicone tubes subjected to hemodynamic flow conditions and deployment of a self-expanding nitinol stents. Verification of bioreactor design through computational fluid dynamics analysis confirmed the application of pulsatile flow with minimum oscillations. EC responses based on morphology, nitric oxide (NO) release, metabolic activity, and cell count on day 1 and day 4 verified the presence of hemodynamic flow conditions. For the first time, it is also demonstrated that the designed bioreactor is capable of capturing EC responses to stent deployment beyond a 24-hour period with this testbed. A temporal investigation of EC responses to stent implantation from day 1 to day 4 showed significantly lower metabolic activity, EC proliferation, no significant changes to NO levels and EC's aligning locally to edges of stent struts, and random orientation in between the struts. These EC responses were indicative of stent-induced disturbances to local hemodynamics and sustained EC injury response contributing to neointimal growth and development of in-stent restenosis. This study presents a novel computationally informed 3D in vitro testbed to evaluate stent performance in presence of hemodynamic flow conditions found in native peripheral arteries and could help to bridge the gap between the current capabilities of 2D in vitro cell culture models and expensive pre-clinical in vivo models.

Two-Step Geometry Design Method, Numerical Simulations and Experimental Studies of Bioresorbable Stents

The stent-implantation process during angioplasty procedures usually involves clamping the stent onto a catheter to a size that allows delivery to the place inside the artery. Finding the right geometrical form of the stent to ensure good functionality in the open form and to enable the clamping process is one of the key elements in the stent-design process. In the first part of the work, an original two-step procedure for stent-geometry design was proposed. This was due to the necessary selection of a geometry that would provide adequate support to the blood-vessel wall without causing damage to the vessel. Numerical simulations of the crimping and deployment processes were performed to verify the method. At the end of this stage, the optimal stent was selected for further testing. In addition, numerical simulations of selected experimental tests (catheter-crimping process, compression process) were used to verify the obtained geometrical forms. The results of experimental tests on stents produced by the microinjection method are presented. The digital image correlation (DIC) method was used to compare the results of numerical simulation and experimental tests. The two-step modeling approach was found to help select the appropriate geometry of the expanded stent, which is an extremely important step in the design of the crimping process. In the part of the paper where the results obtained by numerical simulation were compared with those gained by experiment and using the DIC method, a good compatibility of the displacement results can be observed. For both longitudinal and transverse (pinch) stent compression, the results practically coincide. The paper presents also the application of the DIC method which significantly expands the research possibilities, allowing for a detailed inspection of the deformation state and, above all, verification of local dangerous areas. This approach significantly increases the possibility of assessing the quality of the stents.

Biodegradable polymer drug-eluting stents versus durable polymer drug-eluting stents for percutaneous coronary intervention: a contemporary registry-based analysis

AIMS

We aimed to compare the long-term outcomes of patients undergoing percutaneous coronary intervention (PCI) with biodegradable polymer drug-eluting stents (BP-DES) versus durable polymer drug-eluting stents (DP-DES).

METHODS AND RESULTS

Among 11 517 PCIs with second-generation DES performed in our institution between 2007 and 2019, we identified 8042 procedures performed using DP-DES and 3475 using BP-DES. The primary outcome was target lesion failure, the composite target lesion revascularization (TLR), target vessel myocardial infarction and death. Propensity score matching was used to create a well-balanced cohort. Mean follow-up was 4.8 years. Of the 3413 matched pairs, 21% were females, and the mean age was 66 years. At 1 year, the primary outcome occurred in 8.3% patients versus 7.1% (P = 0.07), and TLR rate was 3% versus 2% (P = 0.006) in patients with DP-DES and BP-DES respectively. Within 5 years, the primary outcome occurred in 23.1% versus 23.4% (P = 0.44), and the rate of TLR was 7.2% versus 6.5% (P = 0.07) in patients with DP-DES and BP-DES, respectively.

CONCLUSION

Similar rates of the composite outcome were observed throughout the entire follow-up. Target lesion revascularization rates were lower in the BP-DES group at 1-year but equalized within 5 years.

Mechanical properties, in vitro and in vivo biocompatibility analysis of pure iron porous implant produced by metal injection molding: A new eco-friendly feedstock from natural rubber (Hevea brasiliensis)

Metal injection molding (MIM) has become an important manufacturing technology for biodegradable medical devices. As a biodegradable metal, pure iron is a promising biomaterial due to its mechanical properties and biocompatibility. In light of this, we performed the first study that manufactured and evaluated the in vitro and in vivo biocompatibility of samples of iron porous implants produced by MIM with a new eco-friendly feedstock from natural rubber (Hevea brasiliensis), a promisor binder that provides elastic property in the green parts. The iron samples were submitted to tests to determine density, microhardness, hardness, yield strength, and stretching. The biocompatibility of the samples was studied in vitro with adipose-derived mesenchymal stromal cells (ADSCs) and erythrocytes, and in vivo on a preclinical model with Wistar rats, testing the iron samples after subcutaneous implant. Results showed that the manufactured samples have adequate physical, and mechanical characteristics to biomedical devices and they are cytocompatible with ADSCs, hemocompatible and biocompatible with Wistars rats. Therefore, pure iron produced by MIM can be considered a promising material for biomedical applications.

Biodegradable Iron-Based Materials-What Was Done and What More Can Be Done?

Iron, while attracting less attention than magnesium and zinc, is still one of the best candidates for biodegradable metal stents thanks its biocompatibility, great elastic moduli and high strength. Due to the low corrosion rate, and thus slow biodegradation, iron stents have still not been put into use. While these problems have still not been fully resolved, many studies have been published that propose different approaches to the issues. This brief overview report summarises the latest developments in the field of biodegradable iron-based stents and presents some techniques that can accelerate their biocorrosion rate. Basic data related to iron metabolism and its biocompatibility, the mechanism of the corrosion process, as well as a critical look at the rate of degradation of iron-based systems obtained by several different methods are included. All this illustrates as the title says, what was done within the topic of biodegradable iron-based materials and what more can be done.

Functionalization Strategies and Fabrication of Solvent-Cast PLLA for Bioresorbable Stents

Actual polymer bioresorbable stents (BRS) generate a risk of device thrombosis as a consequence of the incomplete endothelialization after stent implantation. The material-tissue interactions are not fully controlled and stent fabrication techniques do not allow personalized medical solutions. This work investigates the effect of different functionalization strategies onto solvent-cast poly(l-lactic acid) (PLLA) surfaces with the capacity to enhance surface endothelial adhesion and the fabrication of 3D printed BRS. PLLA films were obtained by solvent casting and treated thermally to increase mechanical properties. Surface functionalization was performed by oxygen plasma (OP), sodium hydroxide (SH) etching, or cutinase enzyme (ET) hydrolysis, generating hydroxyl and carboxyl groups. A higher amount of carboxyl and hydroxyl groups was determined on OP and ET compared to the SH surfaces, as determined by contact angle and X-ray photoelectron spectroscopy (XPS). Endothelial cells (ECs) adhesion and spreading was higher on OP and ET functionalized surfaces correlated with the increase of functional groups without affecting the degradation. To verify the feasibility of the approach proposed, 3D printed PLLA BRS stents were produced by the solvent-cast direct writing technique.

Designing Better Cardiovascular Stent Materials - A Learning Curve

Cardiovascular stents are life-saving devices and one of the top 10 medical breakthroughs of the 21st century. Decades of research and clinical trials have taught us about the effects of material (metal or polymer), design (geometry, strut thickness, and the number of connectors), and drug-elution on vasculature mechanics, hemocompatibility, biocompatibility, and patient health. Recently developed novel bioresorbable stents are intended to overcome common issues of chronic inflammation, in-stent restenosis, and stent thrombosis associated with permanent stents, but there is still much to learn. Increased knowledge and advanced methods in material processing have led to new stent formulations aimed at improving the performance of their predecessors but often comes with potential tradeoffs. This review aims to discuss the advantages and disadvantages of stent material interactions with the host within five areas of contrasting characteristics, such as 1) metal or polymer, 2) bioresorbable or permanent, 3) drug elution or no drug elution, 4) bare or surface-modified, and 5) self-expanding or balloon-expanding perspectives, as they relate to pre-clinical and clinical outcomes and concludes with directions for future studies.

Bifunctional polymer brush-grafted coronary stent for anticoagulation and endothelialization

At present, cardiovascular stent intervention faces clinical complications such as delayed endothelialization, late thrombosis and restenosis after implantation. In this work, a kind of bifunctional polymer brush-grafted coronary stent with anticoagulant and endothelial functions was developed. First, a block copolymer brush with zwitterionic structure consisting of sulfoethyl methacrylate (SBMA) and glycidyl methacrylate (GMA) was surface-induced grafted onto the surface of bare metal coronary stent by atom transfer radical polymerization. The diethylenetriamine NONOate (DETA NONOate), acted as nitric oxide (NO) donor to promote endothelialization, was then attached to polyglycidyl methacrylate (PGMA) brush by a reactive epoxy group to produce NO. The process of chemical modification and the release behavior of NO were characterized in detail. Moreover, the results of anticoagulant test, cytotoxicity test, endothelial cells (ECs) proliferation test and animal experiment of this bifunctional polymer brush-grafted coronary stent we proposed indicate that the zwitterion modified and NO supplied bifunctional coatings has good anticoagulant property, no cytotoxicity and significant endothelialization effect. This work opens the door to combine biological activity of NO and anticoagulant effect of zwitterions, which has great potential to address post-operative side effects associated with restenosis and late stent thrombosis.

Drug-Eluting Stents and Balloons-Materials, Structure Designs, and Coating Techniques: A Review

Controlled drug delivery is a matter of interest to numerous scientists from various domains, as well as an essential issue for society as a whole. In the treatment of many diseases, it is crucial to control the dosing of a drug for a long time and thus maintain its optimal concentration in the tissue. Heart diseases are particularly important in this aspect. One such disease is an obstructive arterial disease affecting millions of people around the world. In recent years, stents and balloon catheters have reached a significant position in the treatment of this condition. Balloon catheters are also successfully used to manage tear ducts, paranasal sinuses, or salivary glands disorders. Modern technology is continually striving to improve the results of previous generations of stents and balloon catheters by refining their design, structure, and constituent materials. These advances result in the development of both successive models of drug-eluting stents (DES) and drug-eluting balloons (DEB). This paper presents milestones in the development of DES and DEB, which are a significant option in the treatment of coronary artery diseases. This report reviews the works related to achievements in construction designs and materials, as well as preparation technologies, of DES and DEB. Special attention was paid to the polymeric biodegradable materials used in the production of the above-mentioned devices. Information was also collected on the various methods of producing drug release coatings and their effectiveness in releasing the active substance.

Sex-Based Outcomes in Patients With a High Bleeding Risk After Percutaneous Coronary Intervention and 1-Month Dual Antiplatelet Therapy: A Secondary Analysis of the LEADERS FREE Randomized Clinical Trial

Importance

Female sex has been identified as a risk factor for bleeding after percutaneous coronary intervention (PCI) and may have contributed to the underuse of drug-eluting stents in women. This risk may be further enhanced among patients with a high bleeding risk.

Objective

To assess the 2-year outcomes by sex in patients with a high bleeding risk who were enrolled in the LEADERS FREE trial.

Design, Setting, and Participants

This cohort study is a prespecified, sex-based secondary analysis of the LEADERS FREE double-blind, randomized clinical trial that was conducted at 68 sites in 20 countries from December 2012 to May 2014. Patients with a high bleeding risk who underwent PCI and met the trial eligibility criteria were enrolled at the participating sites and followed up for up to 2 years.

Interventions

Patients were randomized 1:1 to either a bare-metal stent or a polymer-free, biolimus A9-eluting drug-coated stent with 1-month of dual antiplatelet therapy.

Main Outcomes and Measures

The primary safety end point was a composite of cardiac death, myocardial infarction, or stent thrombosis. The primary efficacy end point was clinically driven target lesion revascularization. Bleeding was assessed using the Bleeding Academic Research Consortium (BARC) scale, and the source of bleeding was recorded.

Results

A total of 2432 patients with a high bleeding risk were included in the study. Of these patients, the mean (SD) age was 75 (9) years, and 1694 (69.7%) were men and 738 (30.3%) were women. Women and men had similar incidence of the 2-year primary safety (14.7% vs 13.6%; P = .37) and efficacy (9.2% vs 9.5%; P = .70) end points. The drug-coated stent was found to be superior to the bare-metal stent in both sexes, with lower target lesion revascularization (women: 6.3% vs 12.1%; men: 7.0% vs 12.0%; P for interaction = .70) and similar rates of the primary safety end point (women: 12.4% vs 17.0%; men: 12.6% vs 14.5%; P for interaction = .40). Overall, 2-year BARC types 3 to 5 major bleeding (10.2% vs 8.6%; P = .14) was not statistically different between the sexes, but women experienced greater BARC types 3 to 5 major bleeding within the first 30 days (5.1% vs 2.4%; P = .007) and greater vascular access site major bleeding than men (2.2% vs 0.5%; P < .001). In both sexes, vascular (women: hazard ratio [HR], 3.45 [95% CI, 1.51-7.87]; men: HR, 4.14 [95% CI, 1.33-12.95]) and nonvascular major bleeding (women: HR, 3.76 [95% CI, 2.17- 6.53]; men: HR, 4.62 [95% CI, 3.23-6.61]) were associated with greater 2-year mortality.

Conclusions and Relevance

This study found no sex differences in the ischemic outcomes of patients with a high bleeding risk after PCI, but women appeared to demonstrate greater early bleeding and major bleeding from the vascular access site. Both women and men with major bleeding seemed to experience worse 2-year mortality, suggesting that bleeding avoidance strategies should be uniformly adopted for all patients, with close attention dedicated to women to avoid denying them the benefits of PCI.

Trial Registration

ClinicalTrials.gov Identifier: NCT02843633.

Magnetic resonance (MR) safety and compatibility of a novel iron bioresorbable scaffold

Fully bioresorbable scaffolds have been designed to overcome the limitations of traditional drug-eluting stents (DESs), which permanently cage the native vessel wall and pose possible complications. The ultrathin-strut designed sirolimus-eluting iron bioresorbable coronary scaffold system (IBS) shows comparable mechanical properties to traditional DESs and exhibits an adaptive degradation profile during target vessel healing, which makes it a promising candidate in all-comers patient population. For implanted medical devices, magnetic resonance (MR) imaging properties, including MR safety and compatibility, should be evaluated before its clinical use, especially for devices with intrinsic ferromagnetism. In this study, MR safety and compatibility of the IBS scaffold were evaluated based on a series of well-designed in-vitro, ex-vivo and in-vivo experiments, considering possible risks, including scaffold movement, over-heating, image artifact, and possible vessel injury, under typical MR condition. Traditional ASTM standards for MR safety and compatibility evaluation of intravascular devices were referred, but not only limited to that. The unique time-relevant MR properties of bioresorbable scaffolds were also discussed. Possible forces imposed on the scaffold during MR scanning and MR image artifacts gradually decreased along with scaffold degradation/absorption. Rigorous experiments designed based on a scientifically based rationale revealed that the IBS scaffold is MR conditional, though not MR compatible before complete absorption. The methodology used in the present study can give insight into the MR evaluation of magnetic scaffolds (bioresorbable) or stents (permanent).

Recent Advances in Manufacturing Innovative Stents

Cardiovascular diseases are the most distributed cause of death worldwide. Stenting of arteries as a percutaneous transluminal angioplasty procedure became a promising minimally invasive therapy based on re-opening narrowed arteries by stent insertion. In order to improve and optimize this method, many research groups are focusing on designing new or improving existent stents. Since the beginning of the stent development in 1986, starting with bare-metal stents (BMS), these devices have been continuously enhanced by applying new materials, developing stent coatings based on inorganic and organic compounds including drugs, nanoparticles or biological components such as genes and cells, as well as adapting stent designs with different fabrication technologies. Drug eluting stents (DES) have been developed to overcome the main shortcomings of BMS or coated stents. Coatings are mainly applied to control biocompatibility, degradation rate, protein adsorption, and allow adequate endothelialization in order to ensure better clinical outcome of BMS, reducing restenosis and thrombosis. As coating materials (i) organic polymers: polyurethanes, poly(ε-caprolactone), styrene-b-isobutylene-b-styrene, polyhydroxybutyrates, poly(lactide-co-glycolide), and phosphoryl choline; (ii) biological components: vascular endothelial growth factor (VEGF) and anti-CD34 antibody and (iii) inorganic coatings: noble metals, wide class of oxides, nitrides, silicide and carbide, hydroxyapatite, diamond-like carbon, and others are used. DES were developed to reduce the tissue hyperplasia and in-stent restenosis utilizing antiproliferative substances like paclitaxel, limus (siro-, zotaro-, evero-, bio-, amphi-, tacro-limus), ABT-578, tyrphostin AGL-2043, genes, etc. The innovative solutions aim at overcoming the main limitations of the stent technology, such as in-stent restenosis and stent thrombosis, while maintaining the prime requirements on biocompatibility, biodegradability, and mechanical behavior. This paper provides an overview of the existing stent types, their functionality, materials, and manufacturing conditions demonstrating the still huge potential for the development of promising stent solutions.

The OPTIMIZE randomized trial to assess safety and efficacy of the Svelte IDS and RX Sirolimus-eluting coronary stent Systems for the Treatment of atherosclerotic lesions: Trial design and rationale

Coronary stenting without angioplasty pretreatment (direct stenting) may simplify procedures in appropriate lesions. Direct stenting is facilitated by smaller profile coronary stent platforms. The present study was designed for regulatory approval of a novel drug-eluting coronary stent and incorporates both randomized comparison for non-inferiority to an approved predicate device as well as a nested evaluation of subjects eligible for direct stenting. STUDY DESIGN AND OBJECTIVES: Prospective, single-blind, randomized, active-control, multi-center study designed to assess the safety and efficacy of the novel Svelte sirolimus-eluting stent (SES) systems. A total of 1630 subjects with up to 3 target lesions will be randomized 1:1 to the Svelte SES versus either the Xience or Promus everolimus-eluting stents (control). Randomization will be stratified by whether or not a direct stenting strategy is planned by the investigator. The primary endpoint is target lesion failure (TLF) at 12 months post index procedure, defined as cardiac death, target vessel myocardial infarction, or clinically driven target lesion revascularization, and the primary analysis is a non-inferiority test with a non-inferiority margin of 3.58%. Secondary clinical endpoints include individual components of TLF, stent thrombosis and measures of procedural resource utilization including contrast administration, fluoroscopy exposure and procedural resource utilization as well as costs. CONCLUSION: The OPTMIZE Trial will evaluate the safety, efficacy and clinical value of the novel Svelte SES in subjects with up to 3 lesions, and will provide a comparison of direct stenting between randomized devices.

Ni-free, built-in nanotubular drug eluting stents: Experimental and theoretical insights

Stents used for cardiovascular applications are composed of three main elements; a metal, polymer coating and the specific drug component. Nickel-based metals and polymer coatings currently used in the stent market have increased the recurrence of in-stent restenosis and stent failure due to inflammation. In this study, a Ti-8Mn alloy was used to fabricate a nanostructured surface that can be used for drug eluting stents to overcome the hypersensitivity of metals that are currently used in stent making as well as introducing a new built-in nano-drug reservoir instead of polymer coatings. Two different systems were studied: titanium dioxide nanotubes (NTs) and Ti-8Mn oxides NTs. The materials were characterized using field emission electron microscope (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), roughness, wettability and surface energy measurements. Nanoindentation was used to evaluate the mechanical properties of the nanotubes as well as their stability. In-vitro cytotoxicity and cell proliferation assays were used to study the effect of the nanotubes on cell viability. Computational insights were also used to test the blood compatibility using band gap model analysis, comparing the band gap of the materials under investigation with that of the fibrinogen, in order to study the possibility of charge transfer that affects the blood clotting mechanism. In addition, the drug loading capacity of the materials was studied using acetyl salicylic acid as a drug model.

In vitro and in vivo evaluation of a dextran-graft-polybutylmethacrylate copolymer coated on CoCr metallic stent

Introduction: The major complications of stent implantation are restenosis and late stent thrombosis. PBMA polymers are used for stent coating because of their mechanical properties. We previously synthesized and characterized Dextrangraft-polybutylmethacrylate copolymer (Dex-PBMA) as a potential stent coating. In this study, we evaluated the haemocompatibility and biocompatibility properties of Dex-PBMA in vitro and in vivo. Methods: Here, we investigated: (1) the effectiveness of polymer coating under physiological conditions and its ability to release Tacrolimus®, (2) the capacity of Dex-PBMA to inhibit Staphylococcus aureus adhesion, (3) the thrombin generation and the human platelet adhesion in static and dynamic conditions, (4) the biocompatibility properties in vitro on human endothelial colony forming cells ( ECFC) and on mesenchymal stem cells (MSC) and in vivo in rat models, and (5) we implanted Dex-PBMA and Dex-PBMA_TAC coated stents in neointimal hyperplasia restenosis rabbit model. Results: Dex-PBMA coating efficiently prevented bacterial adhesion and release Tacrolimus®. Dex-PBMA exhibit haemocompatibility properties under flow and ECFC and MSC compatibility. In vivo, no pathological foreign body reaction was observed neither after intramuscular nor intravascular aortic implantation. After Dex-PBMA and Dex-PBMA_TAC coated stents 30 days implantation in a restenosis rabbit model, an endothelial cell coverage was observed and the lumen patency was preserved. Conclusion: Based on our findings, Dex-PBMA exhibited vascular compatibility and can potentially be used as a coating for metallic coronary stents.

Radiopaque Fully Degradable Nanocomposites for Coronary Stents

Bioresorbable scaffolds (BRS) were introduced to overcome limitations of current metallic drug-eluting stents and poly-L-lactide (PLLA) has been used in the fabrication of BRS due to its biodegradability and biocompatibility. However, such polymers have weaker mechanical properties as compared to metals, limiting their use in BRS. We hypothesized that nanofillers can be used to enhance the mechanical properties considerably in PLLA. To this end, polymer-matrix composites consisting of PLLA reinforced with 5-20 wt% barium sulfate (BaSO4) nanofillers as a potential BRS material was evaluated. Stearic-acid (SA) modified BaSO4 nanofillers were used to examine the effect of functionalization. Rigid nanofillers improved the tensile modulus and strength of PLLA (60% and 110% respectively), while the use of SA-BaSO4 caused a significant increase (~110%) in the elongation at break. Enhancement in mechanical properties is attributed to functionalization which decreased the agglomeration of the nanofillers and improved dispersion. The nanocomposites were also radiopaque. Finite element analysis (FEA) showed that scaffold fabricated from the novel nanocomposite material has improved scaffolding ability, specifically that the strut thickness could be decreased compared to the conventional PLLA scaffold. In conclusion, BaSO4/PLLA-based nanocomposites could potentially be used as materials for BRS with improved mechanical and radiopaque properties.

Therapeutic Approaches Targeting Inflammation in Cardiovascular Disorders

Cardiovascular disease is a leading cause of morbidity and mortality in the Western world and represents an enormous global health burden. Significant advances have been made in the conservative, medical and surgical management across the range of cardiovascular diseases however the inflammatory components of these diseases have traditionally been neglected. Inflammation is certainly a key component of atherosclerosis, a chronic inflammatory condition, but it is at least correlative and predictive of risk in many other aspects of cardiovascular medicine ranging from heart failure to outcomes following reperfusion strategies. Inflammation therefore represents significant potential for future risk stratification of patients as well as offering new therapeutic targets across cardiovascular medicine. This review explores the role of inflammation in several of the major aspects of cardiovascular medicine focusing on current and possible future examples of the targeting of inflammation in prognosis and therapy. It concludes that future directions of cardiovascular research and clinical practice should seek to identify cohorts of patients with a significant inflammatory component to their cardiovascular condition or reaction to cardiovascular intervention. These patients might benefit from therapeutic strategies mounted against the inflammatory components implicated in their condition.

Probing the complex thermo-mechanical properties of a 3D-printed polylactide-hydroxyapatite composite using in situ synchrotron X-ray scattering

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In situ synchrotron X-ray study of PLA-HAp composite multi-scale thermo-mechanics.

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Mullins effect attributed to non-linear strain interaction of PLA lamella with HAp.

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Reversible PLA phase transformation at ∼60 °C, and irreversible above 92 °C.

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Compression → tension change of PLA lamella strain under tensile load & temperature.

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Addition of HAp filler enhances PLA shape memory effect and mechanical properties.

Polylactide (PLA)-hydroxyapatite (HAp) composite components have attracted extensive attentions for a variety of biomedical applications. This study seeks to explore how the biocompatible PLA matrix and the bioactive HAp fillers respond to thermo-mechanical environment of a PLA-HAp composite manufactured by 3D printing using Fused Filament Fabrication (FFF). The insight is obtained by in situ synchrotron small- and wide- angle X-ray scattering (SAXS/WAXS) techniques. The thermo-mechanical cyclic loading tests (0–20 MPa, 22–56 °C) revealed strain softening (Mullins effect) of PLA-HAp composite at both room and elevated temperatures (<56 °C), which can be attributed primarily to the non-linear deformation of PLA nanometre-scale lamellar structure. In contrast, the strain softening of the PLA amorphous matrix appeared only at elevated temperatures (>50 °C) due to the increased chain mobility. Above this temperature the deformation behaviour of the soft PLA lamella changes drastically. The thermal test (0–110 °C) identified multiple crystallisation mechanisms of the PLA amorphous matrix, including reversible stress-induced large crystal formation at room temperature, reversible coupled stress-temperature-induced PLA crystal formation appearing at around 60 °C, as well as irreversible heating-induced crystallisation above 92 °C. The shape memory test (0–3.75 MPa, 0–70 °C) of the PLA-HAp composite demonstrates a fixing ratio (strain upon unloading/strain before unloading) of 65% and rather a ∼100% recovery ratio, showing an improved shape memory property. These findings provide a new framework for systematic characterisation of the thermo-mechanical response of composites, and open up ways towards improved material design and enhanced functionality for biomedical applications.

Radio-Frequency Safety Assessment of Stents in Blood Vessels During Magnetic Resonance Imaging

Purpose: The purpose of this study was to investigate the need for high-resolution detailed anatomical modeling to correctly estimate radio-frequency (RF) safety during magnetic resonance imaging (MRI). RF-induced heating near metallic implanted devices depends on the electric field tangential to the device (E_tan). E_tan and specific absorption rate (SAR) were analyzed in blood vessels of an anatomical model to understand if a standard gel phantom accurately represents the potential heating in tissues due to passive vascular implants such as stents.

Methods: A numerical model of an RF birdcage body coil and an anatomically realistic virtual patient with a native spatial resolution of 1 mm³ were used to simulate the in vivo electric field at 64 MHz (1.5 T MRI system). Maximum values of SAR inside the blood vessels were calculated and compared with peaks in a numerical model of the ASTM gel phantom to see if the results from the simplified and homogeneous gel phantom were comparable to the results from the anatomical model. E_tan values were also calculated in selected stent trajectories inside blood vessels and compared with the ASTM result.

Results: Peak SAR values in blood vessels were up to ten times higher than those found in the ASTM standard gel phantom. Peaks were found in clinically significant anatomical locations, where stents are implanted as per intended use. Furthermore, E_tan results showed that volume-averaged SAR values might not be sufficient to assess RF safety.

Conclusion: Computational modeling with a high-resolution anatomical model indicated higher values of the incident electric field compared to the standard testing approach. Further investigation will help develop a robust safety testing method which reflects clinically realistic conditions.

Cardiovascular stents: overview, evolution, and next generation

Compared to bare-metal stents (BMSs), drug-eluting stents (DESs) have been regarded as a revolutionary change in coronary artery diseases (CADs). Releasing pharmaceutical agents from the stent surface was a promising progress in the realm of cardiovascular stents. Despite supreme advantages over BMSs, in-stent restenosis (ISR) and long-term safety of DESs are still deemed ongoing concerns over clinically application of DESs. The failure of DESs for long-term clinical use is associated with following factors including permanent polymeric coating materials, metallic stent platforms, non-optimal drug releasing condition, and factors that have recently been supposed as contributory factors such as degradation products of polymers, metal ions due to erosion and degradation of metals and their alloys utilizing in some stents as metal frameworks. Discovering the direct relation between stent materials and associating adverse effects is a complicated process, and yet it has not been resolved. For clinical success it is of significant importance to optimize DES design and explore novel strategies to overcome all problems including inflammatory response, delay endothelialization, and sub-acute stent thrombosis (ST) simultaneously. In this work, scientific reports are reviewed particularly focusing on recent advancements in DES design which covers both potential improvements of existing and recently novel prototype stent fabrications. Covering a wide range of information from the BMSs to recent advancement, this study mostly sheds light on DES's concepts, namely stent composition, drug release mechanism, and coating techniques. This review further reports different forms of DES including fully biodegradable DESs, shape-memory ones, and polymer-free DESs.

Rationale and design of advantage (additional diagnostic value of CT perfusion over coronary CT angiography in stented patients with suspected in-stent restenosis or coronary artery disease progression) prospective study

BACKGROUND

Recent studies demonstrated a significant improvement in the diagnostic performance of coronary CT angiography (CCTA) for the evaluation of in-stent restenosis (ISR). However, coronary stent assessment is still challenging, especially because of beam-hardening artifacts due to metallic stent struts and high atherosclerotic burden of non-stented segments. Adenosine-stress myocardial perfusion assessed by CT (CTP) recently demonstrated to be a feasible and accurate tool for evaluating the functional significance of coronary stenoses in patients with suspected coronary artery disease (CAD). Yet, scarce data are available on the performance of CTP in patients with previous stent implantation.

AIM OF THE STUDY

We aim to assess the diagnostic performance of CCTA alone, CTP alone and CCTA plus CTP performed with a new scanner generation using quantitative invasive coronary angiography (ICA) and invasive fractional flow reserve (FFR) as standard of reference.

METHODS

We will enroll 300 consecutive patients with previous stent implantation, referred for non-emergent and clinically indicated invasive coronary angiography (ICA) due to suspected ISR or progression of CAD in native coronary segments. All patients will be subjected to stress myocardial CTP and a rest CCTA. The first 150 subjects will undergo static CTP scan, while the following 150 patients will undergo dynamic CTP scan. Measurement of invasive FFR will be performed during ICA when clinically indicated.

RESULTS

The primary study end points will be: 1) assessment of the diagnostic performance (diagnostic rate, sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy) of CCTA, CTP, combined CCTA-CTP and concordant CCTA-CTP vs. ICA as standard of reference in a territory-based and patient-based analysis; 2) assessment of sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of CCTA, CTP, combined CCTA-CTP and concordant CCTA-CTP vs. invasive FFR as standard of reference in a territory-based analysis.

CONCLUSIONS

The ADVANTAGE study aims to provide an answer to the intriguing question whether the combined anatomical and functional assessment with CCTA plus CTP may have higher diagnostic performance as compared to CCTA alone in identifying stented patients with significant ISR or CAD progression.

Coronary Stents: History, Design, and Construction

The history of percutaneous coronary intervention (PCI) is marked by rapid technological advancements that have taken place over the past 40 years. After a period of balloon angioplasty, which was marred by risk of abrupt vessel closure and vessel recoil, balloon expandable metal alloy stents were the mainstay of PCI. The introduction of drug eluting stents (DES) targeted in-stent restenosis, a common mode of stent failure, and ushered in the current PCI era. Since the first generation of DES, advances in polymer science and stent design have advanced the field. The current generation of DES has thin struts, are highly deliverable, have biocompatible or absorbable polymers, and outstanding safety and efficacy profiles. In this review, we discuss the technological advancements in stent development, design, and construction, with an emphasis on balloon expandable stents. The aspects of stent properties, metal alloys, bioresorbable vascular scaffolds, drug elution, and polymers will be covered.

In vivo and in vitro analyses of the effects of a novel high-nitrogen low-nickel coronary stent on reducing in-stent restenosis

Currently, percutaneous coronary intervention is an important treatment for coronary heart disease. However, the in-stent restenosis rate is still approximately 10–30% after stenting. Nickel ions from the stent are considered to be associated with in-stent restenosis. Therefore, in the present study, we quantitatively evaluated in-stent restenosis after implanting the novel high-nitrogen low-nickel coronary stent (HNS) and studied the mechanism underlying the reduction in in-stent restenosis by using ELISA and Western blot. The in vivo results showed that the HNS could significantly reduce neointima formation and inflammation as compared to SUS316L stents (316L) at 180 days after implantation in porcine coronary arteries and that vascular endothelial growth factor-A expression in porcine coronary arteries after HNS implantation also decreased. The in vitro results showed that, in the case of the HNS, human umbilical vein endothelial cell (HUVEC) proliferation was lower and lesser IL-6 release was noted from HUVECs at one and three days after culture than in the 316L group. Furthermore, p-STAT3 expression in HUVECs on the HNS surface was downregulated after culture for seven days. Thus, we conclude that the HNS could be a promising alternative coronary stent for percutaneous coronary intervention.

In vitro study of the inflammatory cells response to biodegradable Mg-based alloy extract

Biodegradable Mg-based alloys have shown great potential as bone fixation devices or vascular stents. As implant biomaterials, the foreign body reaction (FBR) is an important issue to be studied, where the inflammatory cells play a key role. Here, we used two inflammatory cell lines i.e. THP-1 cells and THP-1 macrophages, to evaluate the effect of Mg–Nd–Zn–Zr alloy (denoted as JDBM) extracts on cell viability, death modes, cell cycle, phagocytosis, differentiation, migration and inflammatory response. The results showed that high-concentration extract induced necrosis and complete damage of cell function. For middle-concentration extract, cell apoptosis and partially impaired cell function were observed. TNF-α expression of macrophages was up-regulated by co-culture with extract in 20% concentration, but was down-regulated in the same concentration in the presence of LPS stimulation. Interestingly, the production of TNF-α decreased when macrophages were cultured in middle and high concentration extracts independent of LPS. Cell viability was also negatively affected by magnesium ions in JDBM extracts, which was a potential factor affecting cell function. Our results provide new information about the impact of Mg alloy extracts on phenotype of immune cells and the potential mechanism, which should be taken into account prior to clinical applications.

Analysis of trends and prospects regarding stents for human blood vessels

Background

The purpose of this paper is to provide technology trends and information regarding market and prospects in stents used for human blood vessels in Korea and the world.

A stent is a medical device in the form of a cylindrical metal net used to normalize flow when blood or other bodily fluids such as biliary fluids are obstructed in blood vessels, gastrointestinal tracts, etc. by inserting the stent into a narrowed or clogged area. Stents are classified into vascular and non-vascular stents. The coronary artery stent is avascular stent that is used for coronary atherosclerosis.

The demand is increasing for stents to treat diseases such as those affecting the heart and blood vessels of elderly and middle-aged patients. Due to the current shift in the demographic structure caused by an aging society, the prospect for stents seems to be very bright.

The use of a stent designed to prevent acute vascular occlusion and restenosis, which is a side effect of conventional balloon angioplasty, has rapidly become popular because it can prevent acute complications and improve clinical outcomes. Since the initial release of this stent, there have been significant developments in its design, the most notable of which has been the introduction of drug-eluting stents (DES). Bioresorbable scaffolds (BRS) have the potential to introduce a paradigm shift in interventional cardiology, a true anatomical and functional “vascular restoration” instead of an artificial stiff tube encased by a persistent metallic foreign body.

Methods

Data for this research were gathered from primary and secondary sources as well as the databases of the Korea Institute of Science Technology Information (KISTI) located in Seoul, Korea like KISTI Market Report. The sources used for primary research included the databases available from the Korea Institute of Science Technology Information, past industry research services/studies, economic and demographic data, and trade and industry journals. Secondary research was used to supplement and complement the primary research. Interviews were conducted with physicians and surgeons from the key hospitals and senior sale/marketing managers from stent product suppliers in South Korea.

Results

The global stent market is estimated at US $ 7.98 billion in 2016 and is expected to grow at a Compound Annual Growth Rate (CAGR) of 3.8% over the next 5 years. As of 2016, the global market for vascular stents is estimated at $ 7.22 billion, with coronary artery stents accounting for 67.3% of the vascular stent market. Among the coronary artery stents, BRS is notably expected to grow at an annual average rate of 8.8% by 2020, but the global adoption rate of BRS remains low at present. In the Korean market, stents for blood vessels account for most of the market, and the market size of stents for blood vessels in Korea was estimated to be 145 billion won as of 2016.

Conclusions

In comparison to the sales growth rate of other medical devices, the future stent technology market is judged to be higher in growth potential.

The evolution of coronary stents

INTRODUCTION

Percutaneous coronary intervention (PCI) is 40 years old this year. From its humble beginnings of experimental work, PCI has transitioned over years with coronary artery stenting now a standard medical procedure performed throughout the world. Areas covered: The conversion from plain old balloon angioplasty (POBA) to the present era of drug eluting stents (DES) has been driven by many technological advances and large bodies of clinical trial evidence. The journey to present day practice has seen many setbacks, such as acute vessel closure with POBA; rates of instant restenosis with bare metal stents (BMS) and more recently, high rates of stent thrombosis with bioabsorbable platforms. This work discusses POBA, why there was a need for BMS, the use of inhibiting drugs to create 1^st generation DES, the change of components to 2^nd generation DES, the use of absorbable drug reservoirs and platforms, and possible future directions with Prohealing Endothelial Progenitor Cell Capture Stents. Expert commentary: This paper reviews the evolution from the original pioneering work to modern day practice, highlighting landmark trials that changed practice. Modern day contemporary practice is now very safe based on the latest drug eluting stents and supported by large datasets.

Hydrophilic surface modification of coronary stent using an atmospheric pressure plasma jet for endothelialization

The first two authors contributed equally to this study. Bioactivity and cell adhesion properties are major factors for fabricating medical devices such as coronary stents. The aim of this study was to evaluate the advantages of atmospheric-pressure plasma jet in enhancing the biocompatibility and endothelial cell-favorites. The experimental objects were divided into before and after atmospheric-pressure plasma jet treatment with the ratio of nitrogen:argon = 3:1, which is similar to air. The treated surfaces were basically characterized by means of a contact angle analyzer for the activation property on their surfaces. The effect of atmospheric-pressure plasma jet on cellular response was examined by endothelial cell adhesion and XTT analysis. It was difficult to detect any changeable morphology after atmospheric-pressure plasma jet treatment on the surface. The roughness was increased after atmospheric-pressure plasma jet treatment compared to nonatmospheric-pressure plasma jet treatment (86.781 and 7.964 nm, respectively). The X-ray photoelectron spectroscopy results showed that the surface concentration of the C–O groups increased slightly from 6% to 8% after plasma activation. The contact angle dramatically decreased in the atmospheric-pressure plasma jet treated group (22.6 ± 15.26°) compared to the nonatmospheric-pressure plasma jet treated group (72.4 ± 15.26°) ( n = 10, p < 0.05). The effect of the increment in hydrophilicity due to the atmospheric-pressure plasma jet on endothelial cell migration and proliferation was 85.2% ± 12.01% and 34.2% ± 2.68%, respectively, at 7 days, compared to the nonatmospheric-pressure plasma jet treated group (58.2% ± 11.44% in migration, n = 10, p < 0.05). Taken together, the stent surface could easily obtain a hydrophilic property by the atmospheric-pressure plasma jet method. Moreover, the atmospheric-pressure plasma jet might affect re-endothelialization after stenting.

Nanomaterial coatings applied on stent surfaces

The advent of percutaneous coronary intervention and intravascular stents has revolutionized the field of interventional cardiology. Nonetheless, in-stent restenosis, inflammation and late-stent thrombosis are the major obstacles with currently available stents. In order to enhance the hemocompatibility of stents, advances in the field of nanotechnology allow novel designs of nanoparticles and biomaterials toward localized drug/gene carriers or stent scaffolds. The current review focuses on promising polymers used in the fabrication of newer generations of stents with a short synopsis on atherosclerosis and current commercialized stents, nanotechnology's impact on stent development and recent advancements in stent biomaterials is discussed in context.