Vascular Wall Reactions to Coronary Stents-Clinical Implications for Stent Failure

Synthesis and characterization of amine-functionalized graphene as a nitric oxide-generating coating for vascular stents

Drug-eluting stents are commonly utilized for the treatment of coronary artery disease, where they maintain vessel patency and prevent restenosis. However, problems with prolonged vascular healing, late thrombosis, and neoatherosclerosis persist; these could potentially be addressed via the local generation of nitric oxide (NO) from endogenous substrates. Herein, we develop amine-functionalized graphene as a NO-generating coating on polylactic acid (PLA)-based bioresorbable stent materials. A novel catalyst was synthesized consisting of polyethyleneimine and polyethylene glycol bonded to graphene oxide (PEI-PEG@GO), with physicochemical characterization using x-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. In the presence of 10 μM S-nitrosoglutathione (GSNO) or S-nitroso-N-acetylpenicillamine (SNAP), PEI-PEG@GO catalyzed the generation of 62% and 91% of the available NO, respectively. Furthermore, PEI-PEG@GO enhanced and prolonged real-time NO generation from GSNO and SNAP under physiological conditions. The uniform coating of PEI-PEG@GO onto stent material is demonstrated via an optimized simple dip-coating method. The coated PLA maintains good biodegradability under accelerated degradation testing, while the PEI-PEG@GO coating remains largely intact. Finally, the stability of the coating was demonstrated at room temperature over 60 days. In conclusion, the innovative conjugation of polymeric amines with graphene can catalyze the generation of NO from S-nitrosothiols at physiologically relevant concentrations. This approach paves the way for the development of controlled NO-generating coatings on bioresorbable stents in order to improve outcomes in coronary artery disease.

Steps Toward Recapitulating Endothelium: A Perspective on the Next Generation of Hemocompatible Coatings

Endothelium, the lining in this blood vessel, orchestrates three main critical functions such as protecting blood components, modulating of hemostasis by secreting various inhibitors, and directing clot digestion (fibrinolysis) by activating tissue plasminogen activator. No other surface can perform these tasks; thus, the contact of blood and blood-contacting medical devices inevitably leads to the activation of coagulation, often causing device failure, and thromboembolic complications. This perspective, first, discusses the biological mechanisms of activation of coagulation and highlights the efforts of advanced coatings to recapitulate one characteristic of endothelium, hereafter single functions of endothelium and noting necessity of the synergistic integration of its three main functions. Subsequently, it is emphasized that to overcome the challenges of blood compatibility an endothelium-mimicking system is needed, proposing a synergy of bottom-up synthetic biology, particularly synthetic cells, with passive- and bioactive surface coatings. Such integration holds promise for developing advanced biomaterials capable of recapitulating endothelial functions, thereby enhancing the hemocompatibility and performance of blood-contacting medical devices.

A Predictive Toxicokinetic Model for Nickel Leaching from Vascular Stents

In vitro testing methods offer valuable insights into the corrosion vulnerability of metal implants and enable prompt comparison between devices. However, they fall short in predicting the extent of leaching and the biodistribution of implant byproducts under in vivo conditions. Physiologically based toxicokinetic (PBTK) models are capable of quantitatively establishing such correlations and therefore provide a powerful tool in advancing nonclinical methods to test medical implants and assess patient exposure to implant debris. In this study, we present a multicompartment PBTK model and a simulation engine for toxicological risk assessment of vascular stents. The mathematical model consists of a detailed set of constitutive equations that describe the transfer of nickel ions from the device to peri-implant tissue and circulation and the nickel mass exchange between blood and the various tissues/organs and excreta. Model parameterization was performed using (1) in-house-produced data from immersion testing to compute the device-specific diffusion parameters and (2) full-scale animal in situ implantation studies to extract the mammalian-specific biokinetic functions that characterize the time-dependent biodistribution of the released ions. The PBTK model was put to the test using a simulation engine to estimate the concentration-time profiles, along with confidence intervals through probabilistic Monte Carlo, of nickel ions leaching from the implanted devices and determine if permissible exposure limits are exceeded. The model-derived output demonstrated prognostic conformity with reported experimental data, indicating that it may provide the basis for the broader use of modeling and simulation tools to guide the optimal design of implantable devices in compliance with exposure limits and other regulatory requirements.

Risk factors for instent restenosis of sirolimus-coated stents in coronary intervention for patients with unstable angina

To investigate the instent restenosis rate of sirolimus-coated stents in percutaneous coronary intervention (PCI) and risk factors for in-stent restenosis, patients with unstable angina (UA) caused by coronary artery stenosis were enrolled, and all clinical and imaging data were analyzed. Among 143 enrolled patients with UA aged 35-83 (mean 60.9 ± 10.0) years enrolled, there were 114 (79.7%) male and 29 (20.3%) female patients. Arterial stenosis was present in one coronary artery in 6 (4.2%) patients, in two coronary arteries in 20 (14.0%) patients, in three arteries in 116 (81.1%), and in four coronary arteries in 1 (0.7%) patient. Stenting was successfully performed in all (100%) patients, and 181 stents were deployed. The quantitative flow ratio (QFR) was 0.92 ± 0.03 (range 0.84-0.96) immediately after stenting, and the TIMI was grade 3 in all patients. The diameter of the stents deployed ranged 2.25-4 mm (mean 3.04 ± 0.44) with a length ranging 10 mm to 104 mm (mean 32.73 ± 15.5). Follow-up angiography was performed in all patients with a duration of 1-92 (mean 15.0 ± 18.8) months. Instent restenosis ≥ 50% occurred in 25 (17.5%) patients. In univariate logistic regression analysis, significant (P < 0.05) risk factors for instent restenosis ≥ 50% were QFR (OR 0.036, 95% CI 0.13-0.97), stent diameter (OR 0.43, 95% CI 0.18-0.92), hypertension (OR 3.16, 95% CI 1.02-9.82), smoking (OR 0.31, 95% CI 0.11-0.89), and neutrophil count (OR 2.22, 95% CI 1.10-5.44). In multivariate analysis, QFR (OR 0.02, 95% CI 0.002-0.19), stent diameter (OR 0.06, 95% CI 0.005-0.59), hypertension (OR 6.75, 95% CI 1.83-35.72) and neutrophil count (OR 276.07, 95% CI 12.32-10,959.95) were significant (P < 0.05) independent risk factors for instent restenosis ≥ 50%. In conclusion, certain instent restenosis rates occurs after the sirolimus-eluted coronary stent deployment for the treatment of coronary artery stenosis in patients with UA, and quantitative flow ratio after stenting, stent diameter, hypertension, and neutrophil count are significant risk factors for instent restenosis of the sirolimus-coated stents in coronary intervention.

An in vivo investigation on the effects of stent implantation on hematological and hemorheological parameters

BACKGROUND

Even though cardiovascular stenting is widely used for the treatment of coronary artery disease, information on how it can affect the hematological and hemorheological profile is scarce in the literature. Most of the work on this issue is based on theoretical or computational fluid dynamics models, lacking in-depth in vitro and in vivo experimental verification.

OBJECTIVE

This work investigates, in an in vivo setting, the effects of stenting and the implantation time-course on hematological and hemorheological parameters that could potentially compromise the device's functionality and longevity.

METHODS

Custom-made self-expanding nitinol stents were implanted in the common carotid artery of male CD1 mice. Whole blood samples were collected from control (non-stented) and stented animals at 5 and 10 weeks post-implantation. Hematological measurements and blood viscosity, red blood cell aggregation, and deformability were performed using standard techniques.

RESULTS

Implant-induced changes were observed in some of the hematological and hemorheological indices. Blood viscosity seems to have been negatively affected by an increased hematocrit and reduced RBC deformability, at 10 weeks post-implantation, despite a slight decrease in RBC aggregation.

CONCLUSIONS

Although the alterations observed may be the result of the peri-implant inflammatory response, the physiological consequences due to hemorheological changes need to be further investigated.

Clinical characteristics and outcomes in patients with Takayasu arteritis coexisting with myocardial ischemia and neurological symptoms: A multicenter, long-term, follow-up study

Background

The incidence of coexisting myocardial ischemia and neurological symptoms in Takayasu arteritis (TA) is currently unknown. There is no standardized treatment algorithm in complex cases involving the coronary and intracranial arteries.

Objective

This study aimed to describe the clinical characteristics and outcomes in patients with TA coexisting with myocardial ischemia and neurological symptoms.

Methods

We retrospectively collected and assessed 1,580 patients with TA, and enrolled patients with myocardial ischemia and neurological symptoms from January 2002 to December 2021 in several hospitals. The incidence, clinical features, management strategy, and prognosis of these patients were evaluated.

Results

Ninety-four (5.9%, 94/1,580) patients with TA coexisting with myocardial ischemia and neurological symptoms were included in the present study. Imaging results showed that the subclavian arteries were the most frequently affected arteries and 37 patients had intracranial vascular abnormalities, comprising the basilar artery (6.1%, 17/279), middle cerebral artery (2.5%, 7/279), anterior cerebral artery (2.9%, 8/279), and posterior cerebral artery (1.9%, 5/279). Among patients with neurological symptoms, 25 patients underwent percutaneous transluminal angioplasty and 20 patients underwent stent implantation. The most common site of stenosis was the ostial and proximal segments of the coronary artery, with 142 lesions among 188 (75.5%) lesions. Thirty-eight patients adopted interventional therapy, 21 patients underwent surgical treatment, and the remaining 35 patients received conservative treatment. There were 20 (21.27%, 20/94) late deaths during a mean follow-up of 57.79 months. The mortality rate in the conservative treatment group was significantly higher than that in the interventional therapy and surgical treatment groups.

Conclusion

Patients with TA involving both the coronary and intracranial vessels are not rare. Stenosis and occlusion lesions most frequently involve the ostia and proximal segment of the arteries. Severe vascular lesions should be revascularized as soon as possible. These patients should be supplemented with glucocorticoids, antiplatelet, nitrates, and statins.

Finite Element Analysis of Fluid–Structure Interaction in a Model of an L-Type Mg Alloy Stent-Stenosed Coronary Artery System

The coronary stent deployment and subsequent service process is a complex geometric/physical nonlinear and fluid–structure coupling system. Analyzing the distribution of stress–strain on the stent is of great significance in studying the deformation and failure behavior. A coupled system dynamics model comprising stenotic coronary artery vessels and L-type Mg alloy stents was established by applying the polynomial hyperelastic constitutive theory. The nonlinear, significant deformation behavior of the stent was systematically studied. The stress–strain distribution of the coupling system during stent deployment was analyzed. The simulation results show that the edges of the supporting body fixed without a bridge are the weakest zone. The stress changes on the inside of the wave of the supporting body are very large, and the residual stress accumulated in this area is the highest. The peak stress of the plaque and the arterial wall was lower than the damage threshold. The velocity of the blood between the wave crest of the supporting body is large and the streamline distribution is concentrated. In addition, the inner surface pressure on the stent is evenly distributed along its axial dimension. The maximum arterial wall shear stress always appears on the inside of the wave crest of the supporting body fixed with a bridge, and, as such, the largest obstacle to the blood flow is in this zone.

Restenosis after Coronary Stent Implantation: Cellular Mechanisms and Potential of Endothelial Progenitor Cells (A Short Guide for the Interventional Cardiologist)

Coronary stents are among the most common therapies worldwide. Despite significant improvements in the biocompatibility of these devices throughout the last decades, they are prone, in as many as 10–20% of cases, to short- or long-term failure. In-stent restenosis is a multifactorial process with a complex and incompletely understood pathophysiology in which inflammatory reactions are of central importance. This review provides a short overview for the clinician on the cellular types responsible for restenosis with a focus on the role of endothelial progenitor cells. The mechanisms of restenosis are described, along with the cell-based attempts made to prevent it. While the focus of this review is principally clinical, experimental evidence provides some insight into the potential implications for prevention and therapy of coronary stent restenosis.

Modulating mTOR Signaling as a Promising Therapeutic Strategy for Atherosclerosis

For more than a decade, atherosclerosis has been one of the leading causes of death in developed countries. The issue of treatment and prevention of the disease is especially acute. Despite the huge amount of basic and clinical research, a significant number of gaps remain in our understanding of the pathogenesis of atherosclerosis, and only their closure will bring us closer to understanding the causes of the disease at the cellular and molecular levels and, accordingly, to the development of an effective treatment. One of the seemingly well-studied elements of atherogenesis is the mTOR signaling pathway. However, more and more new details are still being clarified. Therapeutic strategies associated with rapamycin have worked well in a number of different diseases, and there is every reason to believe that targeting components of the mTOR pathway may pay off in atherosclerosis as well.

Coronary In-Stent Restenosis: Predictors and Treatment

BACKGROUND

Despite the use of modern drug-eluting stents (DES), in-stent restenosis (ISR) may still occur in as many as 2-10% of percutaneous coronary interventions (PCI) in certain lesion/patient subsets. ISR causes increased morbidity after stent implantation; acute myocardial infarction is a frequent correlate to a clinical ISR, arising in 5-10% of cases. Compared to de novo stenosis, patients with ISR also present more frequently with symptoms of unstable angina pectoris (45% versus 61%). In this article, we discuss the risk factors for ISR and the corresponding diagnostic measures and effective treatment strategies.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed, with special attention to current international guidelines and specialist society recommendations.

RESULTS

The type of implanted stent, the presence of diabetes mellitus, previous bypass surgery, and small vessel caliber are predictors for ISR. In their guidelines, the European specialist societies (ESC/EACTS) recommend repeated PCI with DES implantation or drug-coated balloon (DCB) angioplasty as the methods of choice for the treatment of ISR. This approach is supported by evidence from meta-analyses. The RIBS-IV trial showed that revascularization treatment of the target lesion is needed less often after everolimus-eluting stent (EES) implantation than after DCB dilatation (11 [7.1%] versus 24 [15.6%]; p = 0.015; hazard ratio: 0.43; 95% confidence interval: [0.21; 0.87]).

CONCLUSION

Because the pathogenesis of ISR is multifactorial, differentiated risk stratification is necessary. The identification of patient-, stent-, and lesion-related predictors is particularly important, as the most effective way to combat ISR is to prevent it.

Effect of Arthrospira powders from different producers on the formation of endothelial cell monolayers

Arthrospira platensis (AP) and some of its derived products have well-established biological activities as antioxidants or as agents to reduce cardiovascular disease risk factors. Furthermore, AP products have gained increasing importance as potential anti-cancer agents. However, the ingredients of the available products vary greatly with the origin, the type of production and processing, which could have significant consequences for their biological effects. Therefore, the composition and biological influence of five distinct AP powders, which were acquired commercially or produced at a public biotechnology institute, were investigated in regard to their endothelialization capacity using a cell impedance- (CI) based measurement method. The study revealed that the AP composition and especially the influence on HUVEC proliferation differed significantly between the five AP powders up to 109%.Thus, it could be shown that the method used allows the reliable detection of quantitative differences in biological effects of different AP preparations.

Coronary Stent Strut Fractures: Classification, Prevalence and Clinical Associations

Introduction. The frequency, characteristics and clinical implications of Strut fractures (SFs) remain incompletely understood. Methods and results. A total of 185 (160 patients) newer-generation drug-eluting stents (DES) were imaged. SFs were found in 21 DES (11.4%) and were classified in four patterns: one single stacked strut (41%); two or more stacked struts (23%); deformation without gap (27%); transection (9%). In multivariable analysis, calcific and bifurcation lesions were associated with SF in DES (OR: 3.5 [1.1–11] and 4.0 [2.2–7.2], p < 0.05). Device eccentricity and asymmetry as well as optical coherence tomography (OCT) features of impaired strut healing were also associated with SF. The prevalence of fractures was similar in a set of 289 bioresorbable scaffolds (BRS). In a separate series of 20 device thromboses and 36 device restenoses, the prevalence of SF was higher (61.2% of DES and 66.7% of BRS, p < 0.001 for both), with a higher frequency of complex SF patterns (p < 0.0001). In logistic regression analysis, fractures were a correlate of device complications (p < 0.0001, OR = 24.9 [5.6–111] for DES and OR = 6.0 [1.8–20] for BRS). Discussion. The prevalence of OCT-diagnosed SF was unexpectedly high in the setting of elective controls and it increased by about three-fold in the setting of device failure. Fractures were associated with increased lesion complexity and device asymmetry/eccentricity and were more frequent in the setting of device failure such as restenosis and thrombosis.