Coronary stents: historical development, current status and future directions

Biodegradable polymer versus second-generation durable polymer drug-eluting stents in patients with coronary artery disease: A meta-analysis

AIMS

Biodegradable polymer drug-eluting stents (BP-DES) were developed in hopes of reducing the risk of stent thrombosis. The comparison of this new stent platform with second-generation durable polymer drug-eluting stents (DP-DES) has not been well described. We, therefore, performed a meta-analysis to evaluate the safety and efficacy profiles of BP-DES versus second-generation DP-DES in patients with coronary artery disease.

METHODS AND RESULTS

Electronic database searches were conducted, from their dates of inception to June 2018, to identify randomized controlled trials (RCTs) comparing patients with either BP-DES or second-generation DP-DES. Risk estimates were expressed as risk ratios (RRs) with 95% confidence intervals (CIs). We also performed a landmark analysis beyond 1 year and sensitivity analyses based on different variables. A total of 24,406 patients from 19 RCTs were included in the present meta-analysis. There were no significant differences between BP-DES and second-generation DP-DES for the risks of definite or probable stent thrombosis (RR 0.88; 95% CI, 0.69-1.12; P = 0.29), myocardial infarction (RR 0.97; 95% CI, 0.86-1.09; P = 0.59), cardiac death (RR 1.08; 95% CI, 0.92-1.28; P = 0.34), all-cause death (RR 1.02; 95% CI, 0.91-1.13; P = 0.77), target lesion revascularization (RR 1.05; 95% CI, 0.94-1.17; P = 0.38), and target vessel revascularization (RR 1.05; 95% CI, 0.95-1.16; P = 0.36). Similar outcomes were observed regardless of anti-proliferative drug and duration of dual antiplatelet therapy (all P > 0.05).

CONCLUSION

Our findings demonstrate similar safety and efficacy profiles between BP-DES and second-generation BP-DES, with comparable rates of stent thrombosis.

The effects of stenting on coronary endothelium from a molecular biological view: Time for improvement?

Coronary artery stenting following balloon angioplasty represents the gold standard in revascularization of coronary artery stenoses. However, stent deployment as well as percutaneous transluminal coronary angioplasty (PTCA) alone causes severe injury of vascular endothelium. The damaged endothelium is intrinsically repaired by locally derived endothelial cells and by circulating endothelial progenitor cells from the blood, leading to re‐population of the denuded regions within several weeks to months. However, the process of re‐endothelialization is often incomplete or dysfunctional, promoting in‐stent thrombosis and restenosis. The molecular and biomechanical mechanisms that influence the process of re‐endothelialization in stented segments are incompletely understood. Once the endothelium is restored, endothelial function might still be impaired. Several strategies have been followed to improve endothelial function after coronary stenting. In this review, the effects of stenting on coronary endothelium are outlined and current and future strategies to improve endothelial function after stent deployment are discussed.

An asymmetrical dual coating on the stent prepared by ultrasonic atomization

This study aims to design an asymmetric dual coating (ADC) on the stent by ultrasonic atomization to solve the problem of delayed endothelialization and late or very late stent thrombosis which caused by drug eluting stent (DES) with symmetric coating. Chitosan-loaded monoclonal platelet glycoprotein IIIa receptor antibody SZ-21 coating (CSC) was sprayed on inner surface of stents, and outer surface was sprayed CSC and poly(lactic-co-glycolic acid) (PLGA) loaded with docetaxel (DTX) coating (PDC). The coated surface was uniform without aggregation and no shedding phenomenon either before or after stent expanded. Fluorescence labeling has confirmed that the coating has an asymmetric structure. The cumulative release for SZ-21 and DTX was 40.11% and 27.22% within first 24 h, then DTX became the major released drug from 24 h to 7 d, after released for 28 d about 40% of the SZ-21 and 50% DTX still remained on the coated stent. It achieved that ADC can inhibit thrombosis at earlier period and inhibit vascular smooth muscle cells (VSMCs) proliferation at later period. And that ADC has good hemocompatibility and can significantly inhibit VSMCs proliferation. Finally, 4 and 12 weeks after the stent with ADC implanted into rabbit carotid arteries, it showed that the stent with ADC was safe and could effectively prevent thrombosis and in-stent restenosis. © 2018 Wiley Periodicals, Inc. J. Biomed. Mater. Res. Part B, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 825-837, 2019.

Interventional cardiology: from balloons to stents … and back?

The treatment of coronary artery disease has seen rapid change following the invention of percutaneous coronary intervention (PCI). Since its introduction and widespread adoption for the treatment of coronary artery disease, efforts have been underway to minimise both the acute and long-term complications associated with the procedures, resulting in varying degrees of success over the years. These measures have taken many forms, from the adjunctive drug treatment regimen that patients receive before, during and after procedures to the actual mechanical intervention to the vessels themselves. The current gold standard in the interventional field is second-generation drug-eluting stents. However, with ongoing research into new technologies and trials underway in absorbable and non-stent treatments, it may soon be possible to achieve the goal of leaving no long-term physical implant behind in the artery. This could overcome issues with inflammation associated with permanent foreign body implants and prove less limiting for future treatment if needed.

Fourth update on CT angiography of coronary stents: in vitro evaluation of 24 novel stent types

Background Non-invasive evaluation of coronary stent patency by coronary computed tomography angiography (cCTA) remains challenging. Multiple studies showed that CT technology but also individual stent design strongly influence the assessability of coronary stents by cCTA. Purpose To expand the available data on cCTA characteristics of coronary stents by 24 novel types to help interpreting examinations of patients after stent placement and selecting which stents are suitable for assessment by cCTA. Material and Methods Twenty-four novel coronary stents (17 cobalt-chromium, six stainless-steel, one platinum-chromium) were examined in a coronary phantom. Standard cCTA parameters with stent-specific algorithms were used. Image quality was quantified for each stent using established parameters (in-stent attenuation alteration and visible lumen diameter). Results Most stents (n = 14) showed lumen visibilities of 45-55%. No severe restriction of lumen visibility (>60%) was found. The majority of stents (n = 13) caused only small intraluminal attenuation deviations and no severe alterations (>20%) were found. When grouped by manufacturing material, no significant differences were found between cobalt-chromium and stainless-steel with identical mean visible diameters (1.52 ± 0.17 mm vs. 1.52 ± 0.13 mm) and comparable attenuation alterations (35.04 ± 16.56 HU vs. 21.25 ± 14.60 HU). The only platinum-chromium stent showed a smaller visible diameter (1.23 mm) and higher attenuation alteration (41.70 HU), but was also deemed to be assessable by cCTA. Conclusion All 24 novel evaluated stents are eligible for non-invasive evaluation by cCTA without significant differences between cobalt-chromium and stainless-steel stents. This updated catalogue of CT appearances of current coronary stents may serve as reference when taking care of patients with stents in need of coronary imaging.

Uncertainty Quantification of a Multiscale Model for In-Stent Restenosis

Purpose

Coronary artery stenosis, or abnormal narrowing, is a widespread and potentially fatal cardiac disease. After treatment by balloon angioplasty and stenting, restenosis may occur inside the stent due to excessive neointima formation. Simulations of in-stent restenosis can provide new insight into this process. However, uncertainties due to variability in patient-specific parameters must be taken into account.

Methods

We performed an uncertainty quantification (UQ) study on a complex two-dimensional in-stent restenosis model. We used a quasi-Monte Carlo method for UQ of the neointimal area, and the Sobol sensitivity analysis (SA) to estimate the proportions of aleatory and epistemic uncertainties and to determine the most important input parameters.

Results

We observe approximately 30% uncertainty in the mean neointimal area as simulated by the model. Depending on whether a fast initial endothelium recovery occurs, the proportion of the model variance due to natural variability ranges from 15 to 35%. The endothelium regeneration time is identified as the most influential model parameter.

Conclusion

The model output contains a moderate quantity of uncertainty, and the model precision can be increased by obtaining a more certain value on the endothelium regeneration time. We conclude that the quasi-Monte Carlo UQ and the Sobol SA are reliable methods for estimating uncertainties in the response of complicated multiscale cardiovascular models.

Future of Smart Cardiovascular Implants

Cardiovascular disease remains the leading cause of death in Western society. Recent technological advances have opened the opportunity of developing new and innovative smart stent devices that have advanced electrical properties that can improve diagnosis and even treatment of previously intractable conditions, such as central line access failure, atherosclerosis and reporting on vascular grafts for renal dialysis. Here we review the latest advances in the field of cardiovascular medical implants, providing a broad overview of the application of their use in the context of cardiovascular disease rather than an in-depth analysis of the current state of the art. We cover their powering, communication and the challenges faced in their fabrication. We focus specifically on those devices required to maintain vascular access such as ones used to treat arterial disease, a major source of heart attacks and strokes. We look forward to advances in these technologies in the future and their implementation to improve the human condition.

Modelling drug release from polymer-free coronary stents with microporous surfaces

Traditional coronary drug-eluting stents (DES) are made from metal and are coated with a permanent polymer film containing an anti-proliferative drug. Subsequent to stent deployment in a diseased coronary artery, the drug releases into the artery wall and helps prevent restenosis by inhibiting the proliferation of smooth muscle cells. Although this technology has proven to be remarkably successful, there are ongoing concerns that the presence of a polymer in the artery can lead to deleterious medical complications, such as late stent thrombosis. Polymer-free DES may help overcome such shortcomings. However, the absence of a rate-controlling polymer layer makes optimisation of the drug release profile a particular challenge. The use of microporous stent surfaces to modulate the drug release rate is an approach that has recently shown particularly promising clinical results. In this study, we develop a mathematical model to describe drug release from such stents. In particular, we develop a mathematical model to describe drug release from microporous surfaces. The model predicts a two-stage release profile, with a relatively rapid initial release of most of the drug, followed by a slower release of the remaining drug. In the model, the slow release phase is accounted for by an adsorption/desorption mechanism close to the stent surface. The theoretical predictions are compared with experimental release data obtained in our laboratory, and good agreement is found. The valuable insights provided by our model will serve as a useful guide for designing the enhanced polymer-free stents of the future.

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.

Notoginsenoside R1 inhibits vascular smooth muscle cell proliferation, migration and neointimal hyperplasia through PI3K/Akt signaling

Restenosis caused by neointimal hyperplasia significantly decreases long-term efficacy of percutaneous transluminal angioplasty (PTA), stenting, and by-pass surgery for managing coronary and peripheral arterial diseases. A major cause of pathological neointima formation is abnormal vascular smooth muscle cell (VSMC) proliferation and migration. Notoginsenoside R1 (NGR1) is a novel saponin that is derived from Panax notoginseng and has reported cardioprotective, neuroprotective and anti-inflammatory effects. However, its role in modulating VSMC neointima formation remains unexplored. Herein, we report that NGR1 inhibits serum-induced VSMC proliferation and migration by regulating VSMC actin cytoskeleton dynamics. Using a mouse femoral artery endothelium denudation model, we further demonstrate that systemic administration of NGR1 had a potent therapeutic effect in mice, significantly reducing neointimal hyperplasia following acute vessel injury. Mechanistically, we show that NGR1’s mode of action is through inhibiting the activation of phosphatidylinositol 3-kinase (PI3K)/Akt signaling. Taken together, this study identified NGR1 as a potential therapeutic agent for combating restenosis after PTA in cardiovascular diseases.

Design, preparation and performance of a novel drug-eluting stent with multiple layer coatings

Drug-eluting stents (DESs) can effectively control the harmful effects of coronary artery disease, because of their excellent ability to reduce in-stent restenosis. However, delayed re-endothelialization and late stent thrombosis have caused concern over the safety of DESs. In this study, according to time-ordered pathological responses after stent implantation, a hierarchical multiple drug-eluting stent was designed and prepared to overcome the existing DES limitations. A platelet membrane glycoprotein IIIa monoclonal antibody (SZ-21) and a vascular endothelial growth factor (VEGF₁₂₁) were loaded into the inner coating of 316L stainless steel (316L SS) stents to inhibit thrombosis and promote re-endothelialization; rapamycin (RAPA) was loaded into the third layer to inhibit intima hyperplasia; a drug-free poly-l-lactic acid coating was located on the second and fourth layers and used as sustained release layers. The results showed that the three drugs exhibited sequential release kinetics without significant burst release. RAPA released quickly at the early stage, while SZ-21 and VEGF₁₂₁ achieved a slow and prolonged release. In vitro experiments showed that the stents had excellent hemocompatibility and anti-inflammatory properties, and promoted the proliferation and migration of endothelial cells while inhibiting the proliferation and migration of smooth muscle cells. Finally the stents were implanted in the carotid arteries of New Zealand white rabbits. In vivo results showed that compared to 316L SS stents, the multiple drug-eluting stents could accelerate re-endothelialization and inhibit thrombosis, inflammation and in-stent restenosis after 4 weeks (12.79 ± 2.45% vs. 25.27 ± 4.81%) and 12 weeks (15.87 ± 3.62% vs. 58.84 ± 6.87%). These results indicate that the novel drug-eluting stent with multiple layer coatings will have a highly potential clinical application.

Four-year comparative effectiveness of bare-metal and everolimus-eluting stents in New York

OBJECTIVES

To study four-year outcomes for patients receiving either bare-metal stents (BMS) or everolimus-eluting stents (EES) and to evaluate the comparative effectiveness of BMS versus EES in six "off-label" and two "high-risk" patient subgroups.

BACKGROUND

BMS and EES (a second generation of drug-eluting stent) are used in contemporary practice to treat coronary artery disease. However, little is known about long-term comparative effectiveness between BMS and EES.

METHODS

Using the New York State (NYS) cardiac registries, statewide hospital discharge data, the National Death Index, and the U.S. Census file, we assessed four-year outcomes of BMS versus EES in patients receiving either BMS or EES from July 2008 through December 2009. The outcomes included all-cause mortality, acute myocardial infarction (AMI), target-lesion PCI (TLPCI), and target-vessel coronary artery bypass graft (TVCABG) surgery for a follow-up period of four years (median follow-up of 3.6 years). We compared 9,290 propensity score matched pairs with further adjustment using Cox proportional hazards regression.

RESULTS

Compared with patients receiving BMS, patients receiving EES had a lower rate of four-year mortality (adjusted hazard ratio <AHR>: 0.58, 95% confidence interval <CI>: 0.54-0.63), AMI (AHR: 0.68, 95% CI: 0.61-0.76), TLPCI (AHR: 0.67, 95% CI: 0.60-0.75), and TVCABG (AHR, 0.53, 95% CI: 0.43-0.65). For "off-label" and "high-risk" subgroups, EES was associated with decreased mortality and generally better AMI, TLPCI, and TVCABG outcomes relative to BMS.

CONCLUSIONS

Compared with BMS use, EES use was associated with better four-year outcomes.

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.

The stentable in vitro artery: an instrumented platform for endovascular device development and optimization

Although vascular disease is a leading cause of mortality, in vitro tools for controlled, quantitative studies of vascular biological processes in an environment that reflects physiological complexity remain limited. We developed a novel in vitro artery that exhibits a number of unique features distinguishing it from tissue-engineered or organ-on-a-chip constructs, most notably that it allows deployment of endovascular devices including stents, quantitative real-time tracking of cellular responses and detailed measurement of flow velocity and lumenal shear stress using particle image velocimetry. The wall of the stentable in vitro artery consists of an annular collagen hydrogel containing smooth muscle cells (SMCs) and whose lumenal surface is lined with a monolayer of endothelial cells (ECs). The system has in vivo dimensions and physiological flow conditions and allows automated high-resolution live imaging of both SMCs and ECs. To demonstrate proof-of-concept, we imaged and quantified EC wound healing, SMC motility and altered shear stresses on the endothelium after deployment of a coronary stent. The stentable in vitro artery provides a unique platform suited for a broad array of research applications. Wide-scale adoption of this system promises to enhance our understanding of important biological events affecting endovascular device performance and to reduce dependence on animal studies.

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.

Current status and future direction of biodegradable metallic and polymeric vascular scaffolds for next-generation stents

Because of the increasing incidence of coronary artery disease, the importance of cardiovascular stents has continuously increased as a treatment of this disease. Biodegradable scaffolds fabricated from polymers and metals have emerged as promising materials for vascular stents because of their biodegradability. Although such stent framework materials have shown good clinical efficacy, it is difficult to decide whether polymers or metals are better vascular scaffolds because their properties are different. Therefore, there are still obstacles in the development of biodegradable vascular scaffolds in terms of improving clinical efficacy. This review analyzes the pros and cons of current stent materials with respect to five key factors for next-generation stent and discusses methods of improvement. Furthermore, we discuss biodegradable electronic stents with electrical conductivity, which has been considered unimportant until now, and highlight electrical conductivity as a key factor in the development of next-generation stents.

Bilayered Nanoparticles with Sequential Release of VEGF Gene and Paclitaxel for Restenosis Inhibition in Atherosclerosis

Complete reendothelialization followed by inhibition of smooth muscle cell (SMC) proliferation is considered as an effective therapeutic option to prevent restenosis. We have designed poly(lactide-co-glycolide)-loaded bilayered nanoparticles (NPs) with the ability to sequentially release vascular endothelial growth factor (VEGF)-encoding plasmids from the outer layer and paclitaxel (PTX) from the core to promote endothelial regeneration as well as prevent restenosis. Comparing with conventional NPs, which release VEGF plasmid and PTX simultaneously, we expect that the bilayered NPs could release the VEGF plasmid more rapidly, followed by a delayed release of PTX, resulting in an efficient VEGF gene transfection, which ideally could promote reendothelialization and inhibit excessive SMC growth. Indeed, in the present study, we have observed efficient gene transfection using a model plasmid as well as cell growth attenuation in vitro using Chinese hamster ovary cells. Therapeutic efficacy of the bilayered NPs on restenosis was further evaluated in vivo using a rabbit model of atherosclerosis. The bilayered NPs were administered locally via balloon angioplasty to the injured aortic wall through perfusion. Twenty-eight days after the NP administration, rabbits treated with the bilayered NPs exhibited rapid reendothelialization and inhibition of restenosis, as demonstrated by histological analysis. Increased level of VEGF and decreased level of C-reactive protein, a biological marker that is closely related to atherosclerosis, were also observed from animals treated with the bilayered NPs, implicating ameliorated atherosclerosis. Our results suggest that the VEGF plasmid-/PTX-loaded bilayered NPs exert a beneficial impact on atherosclerotic restenosis by sequentially releasing VEGF and PTX in vivo.

Enabling Precision Cardiology Through Multiscale Biology and Systems Medicine

The traditional paradigm of cardiovascular disease research derives insight from large-scale, broadly inclusive clinical studies of well-characterized pathologies. These insights are then put into practice according to standardized clinical guidelines. However, stagnation in the development of new cardiovascular therapies and variability in therapeutic response implies that this paradigm is insufficient for reducing the cardiovascular disease burden. In this state-of-the-art review, we examine 3 interconnected ideas we put forth as key concepts for enabling a transition to precision cardiology: 1) precision characterization of cardiovascular disease with machine learning methods; 2) the application of network models of disease to embrace disease complexity; and 3) using insights from the previous 2 ideas to enable pharmacology and polypharmacology systems for more precise drug-to-patient matching and patient-disease stratification. We conclude by exploring the challenges of applying a precision approach to cardiology, which arise from a deficit of the required resources and infrastructure, and emerging evidence for the clinical effectiveness of this nascent approach.

Contemporary Drug-Eluting Stent Platforms: Design, Safety, and Clinical Efficacy

First-generation drug-eluting stents significantly improved treatment of coronary disease, decreasing rates of revascularization. This was offset by high rates of late adverse events, driven primarily by stent thrombosis. Research and design improvements of individual DES platform components led to next-generation devices with superior clinical safety and efficacy profiles compared with bare-metal stents and first-generation drug-eluting stents. These design improvements and features are explored, and their resulting clinical safety and efficacy reviewed, focusing on platforms approved by the Food and Drug Administration currently widely used in the United States.

Contemporary Drug-Eluting Stent Platforms: Design, Safety, and Clinical Efficacy

First-generation drug-eluting stents significantly improved treatment of coronary disease, decreasing rates of revascularization. This was offset by high rates of late adverse events, driven primarily by stent thrombosis. Research and design improvements of individual DES platform components led to next-generation devices with superior clinical safety and efficacy profiles compared with bare-metal stents and first-generation drug-eluting stents. These design improvements and features are explored, and their resulting clinical safety and efficacy reviewed, focusing on platforms approved by the Food and Drug Administration currently widely used in the United States.

Basic Concepts and Clinical Outcomes of Drug-Eluting Balloons for Treatment of Coronary Artery Disease: An Overview

The technology of percutaneous coronary intervention for atherosclerotic coronary artery disease has evolved considerably since its inception. Though Drug-Eluting Stent (DES) reduces the rate of restenosis, long-term safety outcomes and persistent restenosis in complex lesion subset remain area of concern. Recently, Drug-Eluting Balloon (DEB) represents a novel treatment strategy for atherosclerotic coronary artery disease. DEB demonstrated its added value in preclinical studies. Inspired by these results, several clinical trials particularly in complex lesion subsets have been started to explore the value of this novel treatment strategy in a broader range of lesions. This review would summarise material compositions and different characteristics and clinical outcomes of currently available DEB.

Facile endothelium protection from TNF-α inflammatory insult with surface topography

Adverse events triggered by the direct contact between blood and synthetic materials constitute a sincere shortcoming of cardiovascular implant technology. A well-connected autologous endothelium, generated through the process of endothelialization, impedes such interaction and endows the implant luminal interface with optimal protection. The endothelialization of artificial substrates is the result of a complex interplay between endothelial cells (ECs), surface topography, and flow-generated wall shear stress (WSS). This is however tainted by the pro-inflammatory signaling, typical of cardiovascular patients, which compromises endothelial integrity and survival. Here, we challenge human endothelial monolayers with the pro-inflammatory factor TNF-α under realistic WSS conditions. In these experimental settings we demonstrate that the simple contact between ECs and an optimized surface geometry can inhibit NF-kB activation downstream of TNF-α yielding increased stability of VE-Cadherin mediated cell-to-cell junctions and of focal adhesions. Therefore the here-presented topographic modification can be implemented on a range of artificial substrates enabling their endothelialization under supra-physiological flow and in the presence of pro-inflammatory insults. These new findings constitute an important step toward achieving the full hemocompatibility of cardiovascular implants.

A Comparison of Fully-Coupled 3D In-Stent Restenosis Simulations to In-vivo Data

We describe our fully-coupled 3D multiscale model of in-stent restenosis, with blood flow simulations coupled to smooth muscle cell proliferation, and report results of numerical simulations performed with this model. This novel model is based on several previously reported 2D models. We study the effects of various parameters on the process of restenosis and compare with in vivo porcine data where we observe good qualitative agreement. We study the effects of stent deployment depth (and related injury score), reendothelization speed, and simulate the effect of stent width. Also we demonstrate that we are now capable to simulate restenosis in real-sized (18 mm long, 2.8 mm wide) vessel geometries.

Choice of Stent for Percutaneous Coronary Intervention of Saphenous Vein Grafts

Background—

There are limited data on comparison of contemporary drug-eluting stent (DES) platforms, previous generation DES, and bare-metal stents (BMS) for percutaneous coronary intervention in saphenous vein grafts (SVG). We aimed to assess clinical outcomes following percutaneous coronary intervention to SVG in patients receiving bare-metal stents (BMS), first-generation DES, and newer generation DES in a large unselected national data set from the BCIS (British Cardiovascular Intervention Society).

Methods and Results—

Patients undergoing percutaneous coronary intervention to SVG in the United Kingdom from January 2006 to December 2013 were divided into 3 groups according to stent use: BMS, first-generation DES, and newer generation DES group. Study outcomes included in-hospital major adverse cardiovascular events, 30-day mortality, and 1-year mortality. Patients (n=15 003) underwent percutaneous coronary intervention to SVG in England and Wales during the study period. Of these, 38% received BMS, 15% received first-generation DES, and 47% received second-generation DES. The rates of in-hospital major adverse cardiovascular events were significantly lower in patients treated with second-generation DES (odds ratio, 0.51; 95% confidence interval, 0.38–0.68; P <0.001), but not with first-generation DES, compared with BMS-treated patients. Similarly, 30-day mortality (odds ratio, 0.43; 95% confidence interval, 0.32–0.59; P <0.001) and 1-year mortality (odds ratio, 0.60; 95% confidence interval, 0.51–0.71; P <0.001) were lower in patients treated with second-generation DES, but not with first-generation DES, compared with the patients treated with BMS.

Conclusions—

Patients receiving second-generation DES for the treatment SVG disease have lower rates of in-hospital major adverse cardiovascular events, 30-day mortality, and 1-year mortality, compared with those receiving BMS.

Systematic Review and Meta-Analysis of Drug-Eluting Balloon and Stent for Infrapopliteal Artery Revascularization

Background:

Drug-eluting balloon (DEB) and drug-eluting stent (DES) have been proposed for the treatment of infrapopliteal artery disease. We performed a systematic review and meta-analysis of the current available studies investigating outcomes of DEB and DES in the treatment of infrapopliteal artery disease.

Methods:

Multiple databases were systematically searched to identify studies investigating the outcomes of DEB and DES in the treatment of patients with infrapopliteal artery disease. The quality of studies was assessed by Cochrane Collaboration method. The demographic data, risk factors, outcomes, and antiplatelet strategy were extracted.

Results:

Nine studies were identified with 707 and 606 patients in DEB/DES and standard percutaneous balloon angioplasty (PTA)/bare metal stenting (BMS) group, respectively. The risk of target lesion revascularization (TLR; odds ratio [OR] = 0.38, 95% confidence interval [CI]: 0.23-0.63, P < .01), restenosis rate (OR = 0.30, 95% CI: 0.18-0.50, P < .01), and amputation rate (OR = 0.49, 95% CI: 0.29-0.83, P < .01) significantly decreased in the DES group. The overall survival (OR = 0.86, 95% CI: 0.56-1.32, P = .50) was similar in DES and standard PTA/BMS group; TLR (OR = 0.59, 95% CI: 0.32-1.09, P = .09), restenosis rate (OR = 0.49, 95% CI: 0.11-2.14, P = .35), amputation rate (OR = 1.32, 95% CI: 0.51-3.40, P = .57), and overall survival (OR = 1.40, 95% CI: 0.72-2.71, P = .32) were similar in DEB and standard PTA group.

Conclusion:

The present meta-analysis suggests that compared with standard PTA/BMS, DES may decrease the risk of clinically driven TLR, restenosis rate, and amputation rate without any impact on mortality. However, DEB has no obvious advantage in the treatment of infrapopliteal disease. Due to the limitations of our study, more randomized controlled trials, especially those for DEB, are necessary.

A Preliminary Study of the Therapeutic Role of Human Early Fetal Aorta-derived Endothelial Progenitor Cells in Inhibiting Carotid Artery Neointimal Hyperplasia

Background:

Endothelial cell damage is an important pathophysiological step of restenosis after angioplasty and stenting. Cell transplantation has great therapeutic potential for endothelial recovery. We investigated the effect of transplanting endothelial progenitor cells (EPCs) derived from human early fetal aortas in rat injured arteries.

Methods:

The carotid arterial endothelium of Sprague-Dawley rats was damaged by dilatation with a 1.5 F balloon catheter, and then EPCs derived from human early fetal aortas (<14 weeks) were injected into the lumen of the injured artery in transplanted rats, with an equal volume of normal saline injected into control rats. Rats were sacrificed at 2 and 4 weeks after treatment and transplanted cells were identified by immunohistochemical staining with anti-human CD31 and anti-human mitochondria antibodies. Arterial cross-sections were analyzed by pathology, immunohistochemistry, and morphometry.

Results:

Green fluorescence-labeled EPCs could be seen in the endovascular surface of balloon-injured vessels after transplantation. The intimal area and intimal/medial area ratio were significantly smaller in the transplanted group than in the control (P < 0.05) and the residual lumen area was larger (P < 0.05). After EPC transplantation, a complete vascular endothelial layer was formed, which was positive for human von Willebrand factor after immunohistochemical staining, and immunohistochemical staining revealed many CD31- and mitochondria-positive cells in the re-endothelialized endothelium with EPC transplantation but not control treatment.

Conclusion:

EPCs derived from human early fetal aorta were successfully transplanted into injured vessels and might inhibit neointimal hyperplasia after vascular injury.

DESyne novolimus-eluting coronary stent is superior to Endeavor zotarolimus-eluting coronary stent at five-year follow-up: final results of the multicentre EXCELLA II randomised controlled trial

AIMS

Newer-generation drug-eluting stents (DES) have been shown to be superior to first-generation DES. Current-generation DES have zotarolimus, everolimus or biolimus as antiproliferative drugs. Novolimus, a metabolite of sirolimus, has been specifically developed to provide efficacy similar to currently available agents at a lower dose and thus requires a lower polymer load. We report the final five-year outcomes of the EXCELLA II trial comparing a zotarolimus-eluting stent (ZES) with a novolimus-eluting stent (NES).

METHODS AND RESULTS

EXCELLA II is a prospective, multicentre, single-blind, non-inferiority clinical trial. Patients (n=210) with a maximum of two de novo lesions in two different epicardial vessels were randomised (2:1) to treatment with either NES (n=139) or ZES (n=71). At five-year follow-up, patients in the NES group had a significantly lower incidence of the patient-oriented (HR 0.53, 95% CI: 0.32-0.87, p=0.013) and device-oriented (HR 0.38, 95% CI: 0.17-0.83, p=0.011) composite endpoints. There was no difference in cardiac death and definite/probable stent thrombosis between the two groups; however, there was a trend towards reduction in myocardial infarction and repeat revascularisation in the NES group at five-year follow-up.

CONCLUSIONS

At five-year follow-up, the incidence of device- and patient-oriented events was significantly lower in the NES group. Further studies, adequately powered for clinical outcomes, are warranted.

Bioresorbable Scaffolds: Current Evidences in the Treatment of Coronary Artery Disease

Percutaneous coronary revascularization strategies have gradually progressed over a period of last few decades. The advent of newer generation drug-eluting stents has significantly improved the outcomes of Percutaneous Coronary Intervention (PCI) by substantially reducing in-stent restenosis and stent thrombosis. However, vascular inflammation, restenosis, thrombosis, and neoatherosclerosis due to the permanent presence of a metallic foreign body within the artery limit their usage in complex Coronary Artery Disease (CAD). Bioresorbable Scaffolds (BRS) represent a novel approach in coronary stent technology. Complete resorption of the scaffold liberates the treated vessel from its cage and restores pulsatility, cyclical strain, physiological shear stress, and mechanotransduction. In this review article, we describe the advances in this rapidly evolving technology, present the evidence from the pre-clinical and clinical evaluation of these devices, and provide an overview of the ongoing clinical trials that were designed to examine the effectiveness of BRS in the clinical setting.

Shear-mediated platelet activation in the free flow: Perspectives on the emerging spectrum of cell mechanobiological mechanisms mediating cardiovascular implant thrombosis

Shear-mediated platelet activation (SMPA) is central in thrombosis of implantable cardiovascular therapeutic devices. Despite the morbidity and mortality associated with thrombosis of these devices, our understanding of mechanisms operative in SMPA, particularly in free flowing blood, remains limited. Herein we present and discuss a range of emerging mechanisms for consideration for "free flow" activation under supraphysiologic shear. Further definition and manipulation of these mechanisms will afford opportunities for novel pharmacologic and mechanical strategies to limit SMPA and enhance overall implant device safety.

Biodegradable Metals for Cardiovascular Stents: from Clinical Concerns to Recent Zn-Alloys

Metallic stents are used to promote revascularization and maintain patency of plaqued or damaged arteries following balloon angioplasty. To mitigate the long-term side effects associated with corrosion-resistant stents (i.e., chronic inflammation and late stage thrombosis), a new generation of so-called "bioabsorbable" stents is currently being developed. The bioabsorbable coronary stents will corrode and be absorbed by the artery after completing their task as vascular scaffolding. Research spanning the last two decades has focused on biodegradable polymeric, iron-based, and magnesium-based stent materials. The inherent mechanical and surface properties of metals make them more attractive stent material candidates than their polymeric counterparts. A third class of metallic bioabsorbable materials that are based on zinc has been introduced in the last few years. This new zinc-based class of materials demonstrates the potential for an absorbable metallic stent with the mechanical and biodegradation characteristics required for optimal stent performance. This review compares bioabsorbable materials and summarizes progress towards bioabsorbable stents. It emphasizes the current understanding of physiological and biological benefits of zinc and its biocompatibility. Finally, the review provides an outlook on challenges in designing zinc-based stents of optimal mechanical properties and biodegradation rate.

Comparison of zotarolimus- and everolimus-eluting coronary stents: final 5-year report of the RESOLUTE all-comers trial

Supplemental Digital Content is available in the text.

Background—

Newer-generation drug-eluting stents that release zotarolimus or everolimus have been shown to be superior to the first-generation drug-eluting stents. However, data comparing long-term safety and efficacy of zotarolimus- (ZES) and everolimus-eluting stents (EES) are limited. RESOLUTE all-comers (Randomized Comparison of a Zotarolimus-Eluting Stent With an Everolimus-Eluting Stent for Percutaneous Coronary Intervention) trial compared these 2 stents and has shown that ZES was noninferior to EES at 12-month for the primary end point of target lesion failure. We report the secondary clinical outcomes at the final 5-year follow-up of this trial.

Methods and Results—

RESOLUTE all-comer clinical study is a prospective, multicentre, randomized, 2-arm, open-label, noninferiority trial with minimal exclusion criteria. Patients (n=2292) were randomly assigned to treatment with either ZES (n=1140) or EES (n=1152). Patient-oriented composite end point (combination of all-cause mortality, myocardial infarction, and any revascularizations), device-oriented composite end point (combination of cardiac death, target vessel myocardial infarction, and clinically indicated target lesion revascularization), and major adverse cardiac events (combination of all-cause death, all myocardial infarction, emergent coronary bypass surgery, or clinically indicated target lesion revascularization) were analyzed at 5-year follow-up. The 2 groups were well-matched at baseline. Five-year follow-up data were available for 98% patients. There were no differences in patient-oriented composite end point (ZES 35.3% versus EES 32.0%, P=0.11), device-oriented composite end point (ZES 17.0% versus EES 16.2%, P=0.61), major adverse cardiac events (ZES 21.9% versus EES 21.6%, P=0.88), and definite/probable stent thrombosis (ZES 2.8% versus EES 1.8%, P=0.12).

Conclusions—

At 5-year follow-up, ZES and EES had similar efficacy and safety in a population of patients who had minimal exclusion criteria.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00617084.

Surface Modification of Biodegradable Polymers towards Better Biocompatibility and Lower Thrombogenicity

Purpose

Drug-eluting stents (DES) based on permanent polymeric coating matrices have been introduced to overcome the in stent restenosis associated with bare metal stents (BMS). A further step was the development of DES with biodegradable polymeric coatings to address the risk of thrombosis associated with first-generation DES. In this study we evaluate the biocompatibility of biodegradable polymer materials for their potential use as coating matrices for DES or as materials for fully bioabsorbable vascular stents.

Materials and Methods

Five different polymers, poly(L-lactide) PLLA, poly(D,L-lactide) PDLLA, poly(L-lactide-co-glycolide) P(LLA-co-GA), poly(D,L-lactide-co-glycolide) P(DLLA-co-GA) and poly(L-lactide-co-ε-caprolactone), P(LLA-co-CL) were examined in vitro without and with surface modification. The surface modification of polymers was performed by means of wet-chemical (NaOH and ethylenediamine (EDA)) and plasma-chemical (O₂ and NH₃) processes. The biocompatibility studies were performed on three different cell types: immortalized mouse fibroblasts (cell line L929), human coronary artery endothelial cells (HCAEC) and human umbilical vein endothelial cells (HUVEC). The biocompatibility was examined quantitatively using in vitro cytotoxicity assay. Cells were investigated immunocytochemically for expression of specific markers, and morphology was visualized using confocal laser scanning (CLSM) and scanning electron (SEM) microscopy. Additionally, polymer surfaces were examined for their thrombogenicity using an established hemocompatibility test.

Results

Both endothelial cell types exhibited poor viability and adhesion on all five unmodified polymer surfaces. The biocompatibility of the polymers could be influenced positively by surface modifications. In particular, a reproducible effect was observed for NH₃-plasma treatment, which enhanced the cell viability, adhesion and morphology on all five polymeric surfaces.

Conclusion

Surface modification of polymers can provide a useful approach to enhance their biocompatibility. For clinical application, attempts should be made to stabilize the plasma modification and use it for coupling of biomolecules to accelerate the re-endothelialization of stent surfaces in vivo.