Thin-capped atheromata with reduced collagen content in pigs develop in coronary arterial regions exposed to persistently low endothelial shear stress

Defining "Vulnerable" in coronary artery disease: predisposing factors and preventive measures

The likelihood of a plaque to cause an acute coronary syndrome (ACS) depends on several factors, both lesion- and patient-related. One of the most investigated and established contributing factors is the presence of high-risk or "vulnerable plaque" characteristics, which have been correlated with increased incidence of major adverse cardiovascular events (MACE). The recognition, however, that a significant percentage of vulnerable plaques do not result in causing clinical events has led the scientific community towards the more multifaceted concept of "vulnerable patients". Incorporating the morphological features of an atherosclerotic plaque into its hemodynamic surroundings can better predict the chance of its disruption, as altered fluid dynamics play a significant role in plaque destabilization. The advances in coronary imaging and the field of computational fluid dynamics (CFD) can contribute to develop more accurate lesion- and patient-related ACS prediction models that take into account both the morphology of a plaque and the forces applied upon it. The aim of this review is to provide the latest data regarding the aforementioned predictive factors as well as relevant preventive measures.

Dual-layer alginate hydrogel dressings with chitosan nanofibers for enhanced wound healing, infection prevention, and controlled drug release

An ideal wound dressing should possess high mechanical properties, biocompatibility, and antibacterial and anti-inflammatory properties while being simple and affordable. So, a dual-layer hydrogel-nanofiber wound dressing was fabricated in this study. The hydrogel as the inner layer was prepared using sodium alginate and guar gum, while the nanofiber layer was made of polyvinyl alcohol and chitosan enriched with Ciprofloxacin. Besides the biological and morphological characteristics, the films were evaluated for mechanical properties and swelling behavior and in-vivo experiments were conducted to investigate their wound healing ability. Compared to single-layer hydrogel, the bi-layer hydrogel-nanofiber exhibited excellent mechanical properties, a proportional swelling rate, and water vapor transmission rate, slow degradation towards tissue regeneration, and anti-inflammatory and antimicrobial properties. Tensile strength and elongation at break improved from 0.163 ± 0.55 MPa and 16.869 ± 0.48 % to 1.674 ± 0.41 MPa and 34.062 ± 0.33 %, respectively (p < 0.05). The drug release profile showed an initial burst of 35 ± 1 % within the first hour, followed by controlled release over 24 h. Hemolysis rates were below 2 %, with 1.13 ± 0.03 % for hydrogel-nanofibers, demonstrating excellent blood compatibility. Bi-layer hydrogel-nanofiber significantly enhanced wound healing in rats, resulting in minimal wound surface and denser collagen deposits. Reductions in IL-1β and IL-6 (p < 0.05), confirmed the films' efficacy in wound healing and inflammation mitigation.

Angiogenesis within atherosclerotic plaques: Mechanical regulation, molecular mechanism and clinical diagnosis

Atherosclerosis (AS) is a disease characterized by focal cholesterol accumulation and insoluble inflammation in arterial intima, leading to the formation of an atherosclerotic plaque consisting of lipids, cells, and fibrous matrix. The presence of plaque can restrict or obstruct blood flow, resulting in arterial stenosis and local mechanical microenvironment changes including flow shear stress, vascular matrix stiffness, and plaque structural stress. Neovascularization within the atherosclerotic plaque plays a crucial role in both plaque growth and destabilization, potentially leading to plaque rupture and fatal embolism. However, the exact interactions between neovessels and plaque remain unclear. In this review, we provide a comprehensive analysis of the origin of intraplaque neovessels, the contributing factors, underlying molecular mechanisms, and associated signaling pathways. We specifically emphasize the role of mechanical factors contributing to angiogenesis in atherosclerotic plaques. Additionally, we summarize the imaging techniques and therapeutic strategies for intraplaque neovessels to enhance our understanding of this field.

Synergistic antibacterial and wound healing effects of chitosan nanofibers with ZnO nanoparticles and dual antibiotics

One concern that has been considered potentially fatal is bacterial infection. In addition to the development of biocompatible antibacterial dressings, the screening and combination of new antibiotics effective against antibiotic resistance are crucial. In this study, designing hemostasis electrospun composite nanofibers containing chitosan (CS), polyvinyl pyrrolidone (PVP) and Gelatin (G) as the major components of hydrogel and natural nanofibrillated sodium alginate (SA)/polyvinyl alcohol (PVA) and ZnO nanoparticles (ZnONPs) combination as the nanofiller ingredient, has been investigated which demonstrated significant potential for accelerating wound healing. The hydrogels were developed for the delivery of the amikacin and cefepime antibiotics, along with zinc oxide nanoparticles that were applied to an electrospun layer. Amikacin is a highly effective aminoglycoside antibiotic, particularly for hospital-acquired infections, but its use is limited due to its toxicity. By utilizing it in low concentrations in the form of nanofibers and combining it with cefepime, which exhibits synergistic effects, enhanced efficacy against bacterial pathogens is achieved while potentially minimizing cytotoxicity compared to individual antibiotics. This dressing demonstrated efficient drug release, flexibility, and good swelling properties, indicating its suitable mechanical properties for therapeutic applications. After applying the biocompatible hydrogel to wounds, a significant acceleration in wound closure was observed within 14 days compared to the control group. Furthermore, the notable antibiotic and anti-inflammatory properties underscore its effectiveness in wound healing, making it a promising candidate for medical applications.

Whys and Wherefores of Coronary Arterial Positive Remodeling

Positive remodeling (PR) is an atherosclerotic plaque feature defined as an increase in arterial caliber at the level of an atheroma, in response to increasing plaque burden. The mechanisms that lead to its formation are incompletely understood, but its role in coronary atherosclerosis has major clinical implications. Indeed, plaques with PR have elevated risk of provoking acute cardiac events. Hence, PR figures among the high-risk plaque features that cardiac imaging studies should report. This review aims to provide an overview of the current literature on coronary PR. It outlines the pathophysiology of PR, the different techniques used to assess its presence, and the imaging findings associated to PR, on both noninvasive and invasive studies. This review also summarizes clinical observations, trials, and studies, focused on the impact of PR on clinical outcome.

Comparison of stable carotid plaques in patients with mild-to-moderate carotid stenosis with vulnerable plaques in patients with significant carotid stenosis

To compare the characteristics of stable and vulnerable carotid plaques, and investigate the diagnostic performance of wall shear stress (WSS) based on magnetic resonance plaque imaging in carotid plaques. Retrospectively analyzed and divided 64 atherosclerotic plaques into stable carotid plaque groups with mild-to-moderate stenosis and vulnerable carotid plaque groups with significant stenosis. Computational fluid dynamics simulations were performed to calculate WSS parameters by using three-dimensional wall geometry based on high-resolution magnetic resonance plaque imaging of carotid bifurcation and patient specific boundary conditions obtained through color Doppler ultrasound. WSS parameters including upstream (WSSup), downstream (WSSdown), and core (WSScore) of plaque. The WSS parameters values were compared between the stable and vulnerable carotid plaque groups. Receiver operating characteristic curves and area under the curve (ROC-AUC) and Python were used to evaluate discriminative efficacy of WSS. WSSdown exhibited significant decrease in the vulnerable carotid plaque group (2.88 ± 0.41 Pa) compared to the stable carotid plaque group (4.47 ± 0.84 Pa) (P = .003). The difference of WSSup (3.28 ± 0.85 Pa vs 4.02 ± 0.74 Pa) and WSScore (1.12 ± 0.18 Pa vs 1.38 ± 0.38 Pa) between the two groups were also pronounced (P = .02, 0.01, respectively). The ROC-AUC values for WSSup, WSSdown, WSScore were 0.75 (95% CI, 0.58-0.93), 0.96 (95% CI, 0.79-1.14), 0.69 (95% CI, 0.56-0.83) respectively. When the value of WSSdown was 3.5 Pa, the sensitivity was 93.7% (95% CI, 76.1-111), specificity and accuracy was 87.5% (95% CI, 70.0-105), 88.4% (95% CI, 70.6-105) respectively. Notably, among these parameters, WSSdown demonstrated the highest discriminative efficiency with a F1 Score of 0.90, Diagnostic Odds Ratio of 105.0 and Matthews Correlation Coefficient of 0.81. Vulnerable carotid plaques with significant stenosis have lower WSS compared to stable plaques with mild-to-moderate stenosis, and downstream WSS showing the highest diagnostic efficacy.

Nano hydrogel with bacterial nanocellulose and bitter almond oil nanoemulsions for enhanced wound healing: In-vivo and in-vitro characterization

Biocompatibility, good mechanical properties, infection prevention, and anti-inflammatory are the requirements of an ideal wound dressing for the care and treatment of skin wounds. In this study, the nanohydrogels as wound dressing, were fabricated by bacterial nanocellulose (BNC), polyvinyl alcohol (PVA), and gellan gum. Bitter almond oil nanoemulsion (BAO-NE) was made with ultrasonic force and incorporated into the nanohydrogels in concentrations of 2, 4, and 6 %. The mechanical and physicochemical analyses such as tensile strength (TS), elongation at break (EB), swelling, water vapor transmission rate (WVTR), degradation, FTIR-ATR, and SEM, and anti-inflammatory, antibacterial, etc. properties of the nanohydrogels were investigated. Also, the wound healing ability was evaluated by in-vivo analyses. The molecular analyses of the expression of genes related to collagen production and inflammation were performed. Increasing BAO-NE concentration enhanced anti-inflammatory and antibacterial activities against Gram-negative and Gram-positive bacteria (P < 0.05). The in-vivo study presented the healing role of nanohydrogels in rat wounds. Real-time PCR results confirmed the anti-inflammatory and healing effects of the films at molecular levels. All the results testify to the promising properties of the fabricated nanohydrogels as a potential wound dressing.

A dual-targeting therapeutic nanobubble for imaging-guided atherosclerosis treatment

Atherosclerosis is a cardiovascular disease that seriously endangers human health. Low shear stress (LSS) is recognized as a vital factor in causing chronic inflammatory and further inducing the occurrence and development of atherosclerosis. Targeting imaging and treatment are of substantial significance for the diagnosis and therapy of atherosclerosis. On this ground, a kind of ultrasound (US) imaging-guided therapeutic polymer nanobubbles (NBs) with dual targeting of magnetism and antibody was rationally designed and constructed for the efficiently treating LSS-mediated atherosclerosis. Under the combined targeting effect of an external magnetic field and antibodies, the drug-loaded therapeutic NBs can be effectively accumulated in the inflammatory area caused by LSS. Upon US irradiation, the NBs can be selectively disrupted, leading to the rapid release of the loaded drugs at the targeted site. Notably, the US irradiation generates a cavitation effect that induces repairable micro gaps in nearby cells, thereby enhancing the uptake of released drugs and further improving the therapeutic effect. The prominent US imaging, efficient anti-inflammatory effect and treatment outcome of LSS-mediated atherosclerosis had been verified in vivo on a surgically constructed LSS-atherosclerosis animal model. This work showcased the potential of the designed NBs with multifunctionality for in vivo imaging, dual-targeting, and drug delivery in the treatment of atherosclerosis.

Predicting Lipid-Rich Plaque Progression in Coronary Arteries Using Multimodal Imaging and Wall Shear Stress Signatures

BACKGROUND

Plaque composition and wall shear stress (WSS) magnitude act as well-established players in coronary plaque progression. However, WSS magnitude per se does not completely capture the mechanical stimulus to which the endothelium is subjected, since endothelial cells experience changes in the WSS spatiotemporal configuration on the luminal surface. This study explores WSS profile and lipid content signatures of plaque progression to identify novel biomarkers of coronary atherosclerosis.

METHODS

Thirty-seven patients with acute coronary syndrome underwent coronary computed tomography angiography, near-infrared spectroscopy intravascular ultrasound, and optical coherence tomography of at least 1 nonculprit vessel at baseline and 1-year follow-up. Baseline coronary artery geometries were reconstructed from intravascular ultrasound and coronary computed tomography angiography and combined with flow information to perform computational fluid dynamics simulations to assess the time-averaged WSS magnitude (TAWSS) and the variability in the contraction/expansion action exerted by WSS on the endothelium, quantifiable in terms of topological shear variation index (TSVI). Plaque progression was measured as intravascular ultrasound-derived percentage plaque atheroma volume change at 1-year follow-up. Plaque composition information was extracted from near-infrared spectroscopy and optical coherence tomography.

RESULTS

Exposure to high TSVI and low TAWSS was associated with higher plaque progression (4.00±0.69% and 3.60±0.62%, respectively). Plaque composition acted synergistically with TSVI or TAWSS, resulting in the highest plaque progression (≥5.90%) at locations where lipid-rich plaque is exposed to high TSVI or low TAWSS.

CONCLUSIONS

Luminal exposure to high TSVI, solely or combined with a lipid-rich plaque phenotype, is associated with enhanced plaque progression at 1-year follow-up. Where plaque progression occurred, low TAWSS was also observed. These findings suggest TSVI, in addition to low TAWSS, as a potential biomechanical predictor for plaque progression, showing promise for clinical translation to improve patient prognosis.

Assessment of the nano-mechanical properties of healthy and atherosclerotic coronary arteries by atomic force microscopy

Nano-indentation techniques might be better equipped to assess the heterogeneous material properties of plaques than macroscopic methods but there are no bespoke protocols for this kind of material testing for coronary arteries. Therefore, we developed a measurement protocol to extract mechanical properties from healthy and atherosclerotic coronary artery tissue sections. Young's modulus was derived from force-indentation data. Metrics of collagen fibre density were extracted from the same tissue, and the local material properties were co-registered to the local collagen microstructure with a robust framework. The locations of the indentation were retrospectively classified by histological category (healthy, plaque, lipid-rich, fibrous cap) according to Picrosirius Red stain and adjacent Hematoxylin & Eosin and Oil-Red-O stains. Plaque tissue was softer (p < 0.001) than the healthy coronary wall. Areas rich in collagen within the plaque (fibrous cap) were significantly (p < 0.001) stiffer than areas poor in collagen/lipid-rich, but less than half as stiff as the healthy coronary media. Young's moduli correlated (Pearson's ρ = 0.53, p < 0.05) with collagen content. Atomic force microscopy (AFM) is capable of detecting tissue stiffness changes related to collagen density in healthy and diseased cardiovascular tissue. Mechanical characterization of atherosclerotic plaques with nano-indentation techniques could refine constitutive models for computational modelling.

ITGB2 is a central hub-gene associated with inflammation and early fibro-atheroma development in a swine model of atherosclerosis

Background and aim

The complex dynamic interplay between different biological pathways involved in atherosclerosis development has rendered the identification of specific therapeutic targets a challenging quest. We aimed to identify specific genes and mechanistic pathways associated with the early development of fibro-atheromas in a swine model of atherosclerosis.

Methods

The Wisconsin Miniature Swine™ model of Familial Hypercholesterolemia (WMS-FH, n = 11) and genetically related WMS controls (WMS-N, n = 11) were used. The infrarenal aorta was harvested from both groups for histopathologic and transcriptomic profiling at 12 months. Bioinformatic analysis was performed to identify hub genes and pathways central to disease pathophysiology. The expression of ITGB2, the top ranked hub gene, was manipulated in cell culture and the expression of interconnected genes was tested.

Results

Fibro-atheromatous lesions were documented in all WMS-FH aortic tissues and displayed internal elastic lamina (IEL) disruption, significant reduction of myofibroblast presence and disorganized collagen deposition. No fibro-atheromas were observed in the control group. A total of 266 differentially expressed genes (DEGs) were upregulated in WMS-FH aortic tissues, while 29 genes were downregulated. Top identified hub genes included ITGB2, C1QA, LCP2, SPI1, CSF1R, C5AR1, CTSS, MPEG1, C1QC, and CSF2RB. Overexpression of ITGB2 resulted in elevated expression of other interconnected genes expressed in porcine endothelial cells.

Conclusion

In a swine translational model of atherosclerosis, transcriptomic analysis identified ITGB2 as a central hub gene associated inflammation and early fibroatheroma development making it a potential therapeutic target at this stage of disease.

Development of a Model for Plaque Induction in Rat Carotid Arteries

Objective  Plaque induction through intimal injury using a balloon catheter in small animals and by artificial ligation of the carotid artery in large animals have been reported. However, these reports have not yet succeeded in inducing stable plaques nor creating a high degree of intimal thickening to be used as animal models. We have previously developed a plaque induction model in rats but have failed to obtain a plaque incidence frequency that can be used as a model. Thus, in the current study, we aimed to create a versatile disease model to examine the pharmacokinetics of drug administration, determine the efficacy of treatment, and examine the process of intimal thickening. We also attempted to create an improved model with shorter, more frequent, and more severe intimal thickening. Materials and Methods  The common carotid artery of male Wistar rats was surgically exposed and completely ligated with a wire and 6-0 nylon thread. Then, the wire was removed to create a partial ligation. To create a high frequency and high degree of intimal thickening, 72 rats were divided into two groups: a single lesion group with a 0.25-mm wire and a single ligature point, and a tandem lesion group with a 0.3-mm wire and two ligature points. Each group was further divided into normal diet and high cholesterol diet groups. The presence and frequency of intimal thickening were examined for each group after 4, 8, and 16 weeks of growth. Results  In the single lesion group, intimal thickening was observed in 42% of the 4-week group and 75% of the 8-week group. In the tandem lesion group, intimal thickening was observed in 75% of the 4-week group and 50% of the 8-week group. In addition, 50% of the individuals reared for 16 weeks developed intimal thickening. Conclusion  We successfully induced intimal thickening in the carotid arteries of rats with high frequency in the single lesion and tandem lesion groups. The results also showed that the tandem lesion group tended to induce intimal thickening earlier than the single lesion group.

Fundamental Pathobiology of Coronary Atherosclerosis and Clinical Implications for Chronic Ischemic Heart Disease Management-The Plaque Hypothesis: A Narrative Review

Importance

Recent clinical and imaging studies underscore that major adverse cardiac events (MACE) outcomes are associated not solely with severe coronary obstructions (ischemia hypothesis or stenosis hypothesis), but with the plaque burden along the entire coronary tree. New research clarifies the pathobiologic mechanisms responsible for plaque development/progression/destabilization leading to MACE (plaque hypothesis), but the translation of these insights to clinical management strategies has lagged. This narrative review elaborates the plaque hypothesis and explicates the current understanding of underlying pathobiologic mechanisms, the provocative destabilizing influences, the diagnostic and therapeutic implications, and their actionable clinical management approaches to optimize the management of patients with chronic coronary disease.

Observations

Clinical trials of management strategies for patients with chronic coronary artery disease demonstrate that while MACE rate increases progressively with the anatomic extent of coronary disease, revascularization of the ischemia-producing obstruction does not forestall MACE. Most severely obstructive coronary lesions often remain quiescent and seldom destabilize to cause a MACE. Coronary lesions that later provoke acute myocardial infarction often do not narrow the lumen critically. Invasive and noninvasive imaging can identify the plaque anatomic characteristics (plaque burden, plaque topography, lipid content) and local hemodynamic/biomechanical characteristics (endothelial shear stress, plaque structural stress, axial plaque stress) that can indicate the propensity of individual plaques to provoke a MACE.

Conclusions and Relevance

The pathobiologic construct concerning the culprit region of a plaque most likely to cause a MACE (plaque hypothesis), which incorporates multiple convergent plaque features, informs the evolution of a new management strategy capable of identifying the high-risk portion of plaque wherever it is located along the course of the coronary artery. Ongoing investigations of high-risk plaque features, coupled with technical advances to enable prognostic characterization in real time and at the point of care, will soon enable evaluation of the entire length of the atheromatous coronary artery and broaden the target(s) of our therapeutic intervention to include all regions of the plaque (both flow limiting and nonflow limiting).

Adaptive Wall Shear Stress Imaging in Phantoms, Simulations and In Vivo

WSS measurement is challenging since it requires sensitive flow measurements at a distance close to the wall. The aim of this study is to develop an ultrasound imaging technique which combines vector flow imaging with an unsupervised data clustering approach that automatically detects the region close to the wall with optimally linear flow profile, to provide direct and robust WSS estimation. The proposed technique was evaluated in phantoms, mimicking normal and atherosclerotic vessels, and spatially registered Fluid Structure Interaction (FSI) simulations. A relative error of 6.7% and 19.8% was obtained for peak systolic (WSSPS) and end diastolic (WSSED) WSS in the straight phantom, while in the stenotic phantom, a good similarity was found between measured and simulated WSS distribution, with a correlation coefficient, R, of 0.89 and 0.85 for WSSPS and WSSED, respectively. Moreover, the feasibility of the technique to detect pre-clinical atherosclerosis was tested in an atherosclerotic swine model. Six swines were fed atherogenic diet, while their left carotid artery was ligated in order to disturb flow patterns. Ligated arterial segments that were exposed to low WSSPS and WSS characterized by high frequency oscillations at baseline, developed either moderately or highly stenotic plaques (p < 0.05). Finally, feasibility of the technique was demonstrated in normal and atherosclerotic human subjects. Atherosclerotic carotid arteries with low stenosis had lower WSSPS as compared to control subjects (p < 0.01), while in one subject with high stenosis, elevated WSS was found on an arterial segment, which coincided with plaque rupture site, as determined through histological examination.

Regulation of Collagen I and Collagen III in Tissue Injury and Regeneration

The structure of connective tissues including cartilage, tendons, and ligaments as well as many organs, like the skin, heart, liver, kidney, lungs, blood vessels, and bones, depend on collagen. The bulk of the network of structural proteins that make up the extracellular matrix of the heart is composed of collagen type I and type III, which provide structural support for the muscle cells and are crucial for cardiac function. The prognosis and progression of a disease or diseased state may be significantly impacted by the upregulation or downregulation of the collagen types, particularly Col I and Col III. For example, increasing Col I protein levels may impose increasing myocardial stiffness, impairing the diastolic and systolic function of the myocardium. Collagen I is a stiff fibrillar protein that gives tensile strength, whereas Col III produces an elastic network that stores kinetic energy as an elastic rebound. These two collagen proteins have distinct physical properties in nature. Therefore, the control of Col I and Col III as well as the potential relevance of the Col I/Col III ratio in many biological processes serve as the foundation for this comprehensive review article.

Seх differences in treatment of acute coronary syndrome patients. Data from federal registry of acute coronary syndrome 2016–2019

Introduction. Management of patients with acute coronary syndrome (ACS) is usually universal, regardless of gender, age, and ethnicity. But often in practice, gender and age influence medical decisions, and patients do not receive proper medical care. Medical care for patients with ACS was analyzed by gender according to the federal register of ACS data. Aim. To analyze the influence of the patient's gender on the course of the disease and on the provision of medical care to patients with ACS who underwent treatment in 20162019. Materials and methods. The data of 95 586 cases was analyzed. Two groups were identified: men (n=59 442, 62.2%) and women (n=36 144, 57.8%). Results. Anamnesis analysis has revealed, that women were often more burdened with concomitant diseases and had a higher risk on the GRACE scale at admission. It was demonstrated that men underwent revascularization on average significantly more often than women (51.9% versus 32.5%, respectively, p0.001). In women, conservative therapy was more. When compared with the appropriate use criteria for coronary revascularization, it was shown that more than 70% of women in whom a conservative treatment strategy was chosen, it was expedient to undergo myocardial revascularization using percutaneous coronary intervention. Conclusion. Gender differences were revealed in the course of the disease, as well as in the choice of treatment by doctors. Women are characterized by a later manifestation of the disease, more often in the form of ST-ACS. The course of the disease in women is associated with a higher comorbidity, atypical symptoms and later call for help. A conservative approach prevails in the choice of ACS treatment tactics in women.

An automated software for real-time quantification of wall shear stress distribution in quantitative coronary angiography data

BACKGROUND

Wall shear stress (WSS) estimated in 3D-quantitative coronary angiography (QCA) models appears to provide useful prognostic information and identifies high-risk patients and lesions. However, conventional computational fluid dynamics (CFD) analysis is cumbersome limiting its application in the clinical arena. This report introduces a user-friendly software that allows real-time WSS computation and examines its reproducibility and accuracy in assessing WSS distribution against conventional CFD analysis.

METHODS

From a registry of 414 patients with borderline negative fractional flow reserve (0.81-0.85), 100 lesions were randomly selected. 3D-QCA and CFD analysis were performed using the conventional approach and the novel CAAS Workstation WSS software, and QCA as well as WSS estimations of the two approaches were compared. The reproducibility of the two methodologies was evaluated in a subgroup of 50 lesions.

RESULTS

A good agreement was noted between the conventional approach and the novel software for 3D-QCA metrics (ICC range: 0.73-0-93) and maximum WSS at the lesion site (ICC: 0.88). Both methodologies had a high reproducibility in assessing lesion severity (ICC range: 0.83-0.97 for the conventional approach; 0.84-0.96 for the CAAS Workstation WSS software) and WSS distribution (ICC: 0.85-0.89 and 0.83-0.87, respectively). Simulation time was significantly shorter using the CAAS Workstation WSS software compared to the conventional approach (4.13 ± 0.59 min vs 23.14 ± 2.56 min, p < 0.001).

CONCLUSION

CAAS Workstation WSS software is fast, reproducible, and accurate in assessing WSS distribution. Therefore, this software is expected to enable the broad use of WSS metrics in the clinical arena to identify high-risk lesions and vulnerable patients.

ST-Segment Elevation Myocardial Infarction: Sex Differences in Incidence, Etiology, Treatment, and Outcomes

PURPOSE

Although there have been marked improvements in the standard of care for treatment of ST-elevation myocardial infarction, women, especially younger women, continue to have significantly worse outcomes than men.

RECENT FINDINGS

This review highlights the current sex differences in presentation, etiology, treatment, and outcomes among these patients in order to make providers aware of the heterogeneous entities that cause ST-elevation myocardial infarction particularly in women and of disparities in treatment that lead to poorer outcomes in women. Furthermore, it emphasizes evidence-based strategies including standardized protocols for early revascularization, mechanical circulatory support, and access methodology that can reduce sex-based disparities in treatments and outcomes.

Pig and Mouse Models of Hyperlipidemia and Atherosclerosis

Atherosclerosis is a chronic inflammatory disorder that is the underlying cause of most cardiovascular disease. Resident cells of the artery wall and cells of the immune system participate in atherogenesis. This process is influenced by plasma lipoproteins, genetics, and the hemodynamics of the blood flow in the artery. A variety of animal models have been used to study the pathophysiology and mechanisms that contribute to atherosclerotic lesion formation. No model is ideal as each has its own advantages and limitations with respect to manipulation of the atherogenic process and modeling human atherosclerosis and lipoprotein profile. In this chapter we will discuss pig and mouse models of experimental atherosclerosis. The similarity of pig lipoprotein metabolism and the pathophysiology of the lesions in these animals with that of humans is a major advantage. While a few genetically engineered pig models have been generated, the ease of genetic manipulation in mice and the relatively short time frame for the development of atherosclerosis has made them the most extensively used model. Newer approaches to induce hypercholesterolemia in mice have been developed that do not require germline modifications. These approaches will facilitate studies on atherogenic mechanisms.

Association of Carotid Plaque Vulnerability and Cardiovascular Risk Factors in Patients Undergoing Carotid Endarterectomy

BACKGROUND

The association between high-risk cardiovascular factors and atherosclerotic is well established. However, whether plaque vulnerability is related to specific cardiovascular risk factors remains unknown. The association between plaque vulnerability and cardiovascular risk factors was evaluated in plaques removed in a carotid endarterectomy.

METHODS

Consecutive subjects scheduled for a carotid endarterectomy were recruited. All patients' baseline characteristics, risk factors, laboratory results, cardiovascular disease history, and medication use history were collected preoperatively. Histopathologic features within the vulnerable plaques were analyzed postoperatively. Risk factors for plaque vulnerability were assessed by univariate and multivariate analyses with adjustment for potential confounders.

RESULTS

A total of 128 carotid plaques were removed during the carotid endarterectomy. On multivariate analysis, hypertension (odds ratio [OR] 5.971, 95% confidence interval [CI] 1.959-18.203, P = 0.002) and dyslipidemia (OR 3.822, 95% CI 1.317-11.089, P = 0.014) were independently associated with plaque vulnerability. Hypertension was independently associated with the presence of a ruptured fibrous cap (OR 6.122, 95% CI 2.318-16.166, P < 0.001), intraplaque hemorrhage (OR 3.535, 95% CI 1.551-8.055, P = 0.003), and a large lipid core (OR 2.335, 95% CI 1.053-5.180, P = 0.037). The incidence of having a large lipid core was increased by 3.216-fold in patients with dyslipidemia (95% CI 1.409-7.340, P = 0.006). When the multivariate analysis was restricted to symptomatic patients, hypertension (OR 5.005, 95% CI 1.294-19.350, P = 0.020) was the most significant risk factor associated with vulnerable plaque.

CONCLUSION

The composition heterogeneity in the atherosclerotic plaque was significantly correlated to specific cardiovascular risk factors.

Early Atherosclerotic Changes in Coronary Arteries are Associated with Endothelium Shear Stress Contraction/Expansion Variability

Although unphysiological wall shear stress (WSS) has become the consensus hemodynamic mechanism for coronary atherosclerosis, the complex biomechanical stimulus affecting atherosclerosis evolution is still undetermined. This has motivated the interest on the contraction/expansion action exerted by WSS on the endothelium, obtained through the WSS topological skeleton analysis. This study tests the ability of this WSS feature, alone or combined with WSS magnitude, to predict coronary wall thickness (WT) longitudinal changes. Nine coronary arteries of hypercholesterolemic minipigs underwent imaging with local WT measurement at three time points: baseline (T1), after 5.6 ± 0.9 (T2), and 7.6 ± 2.5 (T3) months. Individualized computational hemodynamic simulations were performed at T1 and T2. The variability of the WSS contraction/expansion action along the cardiac cycle was quantified using the WSS topological shear variation index (TSVI). Alone or combined, high TSVI and low WSS significantly co-localized with high WT at the same time points and were significant predictors of thickening at later time points. TSVI and WSS magnitude values in a physiological range appeared to play an atheroprotective role. Both the variability of the WSS contraction/expansion action and WSS magnitude, accounting for different hemodynamic effects on the endothelium, (1) are linked to WT changes and (2) concur to identify WSS features leading to coronary atherosclerosis.

Coronary Artery Bypass Grafting Following Acute Coronary Syndrome: Impact of Gender

The impact of gender on clinical outcomes after coronary artery bypass grafting (CABG) has generated conflicting results. We investigated the impact of gender, on 30 day mortality, complications and late survival in patients with acute coronary syndrome (ACS) undergoing CABG. The study included 1308 patients enrolled from the biennial Acute Coronary Syndrome Israeli Survey between 2000 and 2016, who were hospitalized for ACS and underwent CABG. Of them, 1045 (80%) were men and 263 (20%) women. While women were older and had more hypertension and hyperlipidemia, they demonstrated less diabetes mellitus, previous ischemic heart disease, smoking, and fewer implicated coronary arteries. Women presented with more atypical symptoms as compared to men (26.3% vs 19.4%, p = 0.017). Overall multivariable-adjusted 30 day mortality was higher in women than in men (OR 2.47 95% CI 1.19-5.1, p = 0.015). Among patients with ST-elevation myocardial infarction (STEMI) or non-STEMI, women had a higher 10 year mortality rate than men (42.5% vs 19.2%, log-rank p < 0.001 and 31.5% vs 20.7%, log-rank, p = 0.012). However, in patients with unstable angina pectoris on admission, these differences were not seen (16.9% vs 13.4%, log-rank p = 0.540). Multivariable analysis demonstrated that female gender was a significant predictor for 10 year mortality (HR 1.39, 95% CI 1.02-1.9, p = 0.038). In a real-life setting, women constitute an independent predictor for short- and long-term mortality following ACS treated by CABG surgery. The reasons for a higher mortality in women should be further investigated as well as specific and/or more intensive therapies after CABG in this high-risk group of patients.

Sex and gender in cardiovascular medicine: presentation and outcomes of acute coronary syndrome

Although health disparities in women presenting with acute coronary syndrome (ACS) have received growing attention in recent years, clinical outcomes from ACS are still worse for women than for men. Women continue to experience higher patient and system delays and receive less aggressive invasive treatment and pharmacotherapies. Gender- and sex-specific variables that contribute to ACS vulnerability remain largely unknown. Notwithstanding the sex differences in baseline coronary anatomy and function, women and men are treated the same based on guidelines that were established from experimental and clinical trial data over-representing the male population. Importantly, younger women have a particularly unfavourable prognosis and a plethora of unanswered questions remains in this younger population. The present review summarizes contemporary evidence for gender and sex differences in vascular biology, clinical presentation, and outcomes of ACS. We further discuss potential mechanisms and non-traditional risk conditions modulating the course of disease in women and men, such as unrecognized psychosocial factors, sex-specific vascular and neural stress responses, and the potential impact of epigenetic modifications.

Experimental evidence and network pharmacology-based analysis reveal the molecular mechanism of Tongxinluo capsule administered in coronary heart diseases

BACKGROUND

Tongxinluo (TXL) capsule, a polypharmacy derived from traditional Chinese medicine (TCM), has been widely used in coronary heart disease (CHD), while the underlying mechanism of TXL capsule is still unclear. The present study aimed at investigating the underlying mechanism of TXL acting on CHD patients and providing substantial evidence in molecular evidence by means of a network pharmacological analysis.

METHOD

Active compounds and targeted genes of TXL were retrieved from TCM systems pharmacology (TCMSP) and TCM integrative database (TCMID). CHD and coronary artery disease were treated as search queries in GeneCards and Online Mendelian Inheritance in Man (OMIM) databases to obtain disease-related genes. Visualization of disease-targets network was performed under administration of Cytoscape software. Besides, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were administered. H9c2 cells were used to validate the predicted results in cardiomyocytes/reoxygenation model, and anti-inflammatory ability was examined.

RESULTS

A network of a total of 212 nodes and 1016 edges was obtained. Peptide and ubiquitin-like protein ligase binding occupied a leading position of GO enrichment. For KEGG analysis, fluid shear stress and atherosclerosis, as well as inflammation-related pathways were enriched. Cellular validation revealed the anti-inflammatory effect of β-sitosterol, eriodictyol, odoricarpin, and tirucallol as active compounds of TXL.

CONCLUSION

Our study provided substantial molecular evidence that TXL capsule possessed the characteristics of multitargets with safe profile, and the main component is capable of regulating cytokine level in CHD patients.

Personalized Clinical Phenotyping through Systems Medicine and Artificial Intelligence

Personalized Medicine (PM) has shifted the traditional top-down approach to medicine based on the identification of single etiological factors to explain diseases, which was not suitable for explaining complex conditions. The concept of PM assumes several interpretations in the literature, with particular regards to Genetic and Genomic Medicine. Despite the fact that some disease-modifying genes affect disease expression and progression, many complex conditions cannot be understood through only this lens, especially when other lifestyle factors can play a crucial role (such as the environment, emotions, nutrition, etc.). Personalizing clinical phenotyping becomes a challenge when different pathophysiological mechanisms underlie the same manifestation. Brain disorders, cardiovascular and gastroenterological diseases can be paradigmatic examples. Experiences on the field of Fondazione Policlinico Gemelli in Rome (a research hospital recognized by the Italian Ministry of Health as national leader in "Personalized Medicine" and "Innovative Biomedical Technologies") could help understanding which techniques and tools are the most performing to develop potential clinical phenotypes personalization. The connection between practical experiences and scientific literature highlights how this potential can be reached towards Systems Medicine using Artificial Intelligence tools.

Evaluation of Plaque Characteristics and Inflammation Using Magnetic Resonance Imaging

Atherosclerosis is an inflammatory disease of large and medium-sized arteries, characterized by the growth of atherosclerotic lesions (plaques). These plaques often develop at inner curvatures of arteries, branchpoints, and bifurcations, where the endothelial wall shear stress is low and oscillatory. In conjunction with other processes such as lipid deposition, biomechanical factors lead to local vascular inflammation and plaque growth. There is also evidence that low and oscillatory shear stress contribute to arterial remodeling, entailing a loss in arterial elasticity and, therefore, an increased pulse-wave velocity. Although altered shear stress profiles, elasticity and inflammation are closely intertwined and critical for plaque growth, preclinical and clinical investigations for atherosclerosis mostly focus on the investigation of one of these parameters only due to the experimental limitations. However, cardiovascular magnetic resonance imaging (MRI) has been demonstrated to be a potent tool which can be used to provide insights into a large range of biological parameters in one experimental session. It enables the evaluation of the dynamic process of atherosclerotic lesion formation without the need for harmful radiation. Flow-sensitive MRI provides the assessment of hemodynamic parameters such as wall shear stress and pulse wave velocity which may replace invasive and radiation-based techniques for imaging of the vascular function and the characterization of early plaque development. In combination with inflammation imaging, the analyses and correlations of these parameters could not only significantly advance basic preclinical investigations of atherosclerotic lesion formation and progression, but also the diagnostic clinical evaluation for early identification of high-risk plaques, which are prone to rupture. In this review, we summarize the key applications of magnetic resonance imaging for the evaluation of plaque characteristics through flow sensitive and morphological measurements. The simultaneous measurements of functional and structural parameters will further preclinical research on atherosclerosis and has the potential to fundamentally improve the detection of inflammation and vulnerable plaques in patients.

Multidirectional wall shear stress promotes advanced coronary plaque development: comparing five shear stress metrics

Aims

Atherosclerotic plaque development has been associated with wall shear stress (WSS). However, the multidirectionality of blood flow, and thus of WSS, is rarely taken into account. The purpose of this study was to comprehensively compare five metrics that describe (multidirectional) WSS behaviour and assess how WSS multidirectionality affects coronary plaque initiation and progression.

Methods and results

Adult familial hypercholesterolaemic pigs (n = 10) that were fed a high-fat diet, underwent imaging of the three main coronary arteries at three-time points [3 (T₁), 9 (T₂), and 10–12 (T₃) months]. Three-dimensional geometry of the arterial lumen, in combination with local flow velocity measurements, was used to calculate WSS at T₁ and T₂. For analysis, arteries were divided into 3 mm/45° sectors (n = 3648). Changes in wall thickness and final plaque composition were assessed with near-infrared spectroscopy–intravascular ultrasound, optical coherence tomography imaging, and histology. Both in pigs with advanced and mild disease, the highest plaque progression rate was exclusively found at low time-averaged WSS (TAWSS) or high multidirectional WSS regions at both T₁ and T₂. However, the eventually largest plaque growth was located in regions with initial low TAWSS or high multidirectional WSS that, over time, became exposed to high TAWSS or low multidirectional WSS at T₂. Besides plaque size, also the presence of vulnerable plaque components at the last time point was related to low and multidirectional WSS. Almost all WSS metrics had good predictive values for the development of plaque (47–50%) and advanced fibrous cap atheroma (FCA) development (59–61%).

Conclusion

This study demonstrates that low and multidirectional WSS promote both initiation and progression of coronary atherosclerotic plaques. The high-predictive values of the multidirectional WSS metrics for FCA development indicate their potential as an additional clinical marker for the vulnerable disease.

The Neuro-Inflammatory-Vascular Circuit: Evidence for a Sex-Dependent Interrelation?

Cardiovascular disease (CVD) is the leading cause of death worldwide with mortality rates in women currently exceeding those in men. To date, evidence is widely lacking for unique female determinants of CVD. However, strong associations with psychological stress, obesity or elevated inflammatory biomarkers with adverse cardiovascular outcomes in women have been identified in various studies. Interestingly, amygdalar metabolic activity, a central neural structure involved in emotional stress processing, has proven to be an independent predictor of major adverse cardiovascular events (MACE). Moreover, upregulated amygdalar metabolism was directly linked to myocardial injury in women, but not in men. This newly suggested sex-dependent brain-heart interrelation was further supported by the discovery that bone marrow activity, a surrogate parameter of inflammation, represents a potential bridging link between amygdalar activity and cardiovascular pathology by fueling inflammatory processes that promote atherosclerotic disease. Such malignant cascade of events might account, at least in part, for the excess female mortality seen in women with coronary artery disease and calls for sex-specific research toward pharmacologic or behavioral modulators to improve cardiovascular outcomes, particularly in women. This mini review summarizes recent advances in cardiovascular sex-specific medicine, thereby focusing on the interplay between the limbic system, autonomic regulation and inflammatory biomarkers, which may help to tailor CVD management toward the female cardiovascular phenotype.

The relationship between residual cholesterol risk and plaque characteristics in patients with acute coronary syndrome: Insights from an optical coherence tomography study

BACKGROUND AND AIMS

The impact of residual cholesterol risk (RCR) on plaque characteristics is not fully understood. The study aims to explore the relationship between RCR and plaque features in patients presenting with acute coronary syndrome (ACS).

METHODS

All ACS patients undergoing pre-intervention optical coherence tomography (OCT) with high-sensitivity C-reactive protein (hs-CRP) <2 mg/L on admission were retrospectively enrolled from January to December 2017, at Beijing Anzhen Hospital, Capital Medical University. RCR was defined as low density lipoprotein cholesterol (LDL-C) ≥1.8 mmol/L. Patients were divided into the RCR and non-RCR groups according to baseline LDL-C.

RESULTS

A total of 90 patients (94 vessels) were included, with 50 in the RCR group and 40 in the non-RCR group, respectively. Compared with the non-RCR group, patients in the RCR group were younger (54.0 ± 11.04 vs. 58.4 ± 9.59, p = 0.049) and had a higher incidence of multivessel disease (6.0% vs. 2.5%, p = 0.028). With regard to plaque characteristics, fibrous plaque (0.0% vs 12.5%, p = 0.003) was less and fibroatheroma (79.6% vs. 50.0%, p = 0.028) was more frequently seen in the RCR group. Patients in the RCR group were more prone to present with plaque rupture (24.1% vs 5.0%, p = 0.008). Cholesterol crystal (22.2% vs 12.5%, p = 0.226) and thin-cap fibroatheroma (25.9% vs. 12.5%, p = 0.109) were more common in the RCR group, though without statistical difference. Multivariate logistic regression showed that RCR (odds ratio [OR]: 7.95, p = 0.011) and smoking (OR: 4.08, p = 0.026) were independent risk factors of plaque rupture in our patients.

CONCLUSIONS

ACS patients with RCR are more likely to have atherosclerotic plaque and plaque rupture, indicating a more vulnerable plaque phenotype.

Relationship between arterial remodelling and serial changes in coronary atherosclerosis by intravascular ultrasound: an analysis of the IBIS-4 study

AIMS

Arterial remodelling is an important determinant of coronary atherosclerosis. Assessment of the remodelling index, comparing a lesion to a local reference site, is a suboptimal correlate of serial vascular changes. We assessed a novel approach which, unlike the local-reference approach, uses the entire artery's global remodelling as reference.

METHODS AND RESULTS

Serial (baseline and 13 months) intravascular ultrasound was performed in 146 non-infarct-related arteries of 82 patients treated with high-intensity statin. Arteries were divided into 3-mm segments (n = 1479), and focal remodelling was characterized in individual segments at both timepoints applying the global arterial reference approach. First, we compared preceding vascular changes in relation to follow-up remodelling. Second, we examined whether baseline remodelling predicts subsequent plaque progression/regression. At follow-up, segments with constrictive vs. compensatory or expansive remodelling had greater preceding reduction of vessel area (-0.67 vs. -0.38 vs. -0.002 mm2; P < 0.001) and lumen area (-0.82 vs. -0.09 vs. 0.40 mm2; P < 0.001). Overall, we found significant regression in percent atheroma volume (PAV) [-0.80% (-1.41 to -0.19)]. Segments with constrictive remodelling at baseline had greater subsequent PAV regression vs. modest regression in the compensatory, and PAV progression in the expansive remodelling group (-6.14% vs. -0.71% vs. 2.26%; P < 0.001). Lesion-level analyses (n = 118) showed no differences when remodelling was defined by the local reference approach at baseline or follow-up.

CONCLUSION

Remodelling assessment using a global arterial reference approach, but not the commonly used, local reference site approach, correlated reasonably well with serial changes in arterial dimensions and identified arterial segments with subsequent PAV progression despite intensive statin treatment and overall atheroma regression.

Homeobox B9 integrates bone morphogenic protein 4 with inflammation at atheroprone sites

AIMS

Atherosclerosis develops near branches and bends of arteries that are exposed to disturbed blood flow which exerts low wall shear stress (WSS). These mechanical conditions alter endothelial cells (EC) by priming them for inflammation and by inducing turnover. Homeobox (Hox) genes are developmental genes involved in the patterning of embryos along their anterior-posterior and proximal-distal axes. Here we identified Hox genes that are regulated by WSS and investigated their functions in adult arteries.

METHODS AND RESULTS

EC were isolated from inner (low WSS) and outer (high WSS) regions of the porcine aorta and the expression of Hox genes was analysed by quantitative real-time PCR. Several Hox genes (HoxA10, HoxB4, HoxB7, HoxB9, HoxD8, HoxD9) were significantly enriched at the low WSS compared to the high WSS region. Similarly, studies of cultured human umbilical vein EC (HUVEC) or porcine aortic EC revealed that the expression of multiple Hox genes (HoxA10, HoxB9, HoxD8, HoxD9) was enhanced under low (4 dyn/cm2) compared to high (13 dyn/cm2) WSS conditions. Gene silencing studies identified Hox genes (HoxB9, HoxD8, HoxD9) that are positive regulators of inflammatory molecule expression in EC exposed to low WSS, and others (HoxB9, HoxB7, HoxB4) that regulated EC turnover. We subsequently focused on HoxB9 because it was strongly up-regulated by low WSS and, uniquely, was a driver of both inflammation and proliferation. At a mechanistic level, we demonstrate using cultured EC and murine models that bone morphogenic protein 4 (BMP4) is an upstream regulator of HoxB9 which elicits inflammation via induction of numerous inflammatory mediators including TNF and downstream NF-κB activation. Moreover, the BMP4-HoxB9-TNF pathway was potentiated by hypercholesterolaemic conditions.

CONCLUSIONS

Low WSS induces multiple Hox genes that control the activation state and turnover of EC. Notably, low WSS activates a BMP4-HoxB9-TNF signalling pathway to initiate focal arterial inflammation, thereby demonstrating integration of the BMP and Hox systems in vascular pathophysiology.

Exploring wall shear stress spatiotemporal heterogeneity in coronary arteries combining correlation-based analysis and complex networks with computational hemodynamics

Atherosclerosis at the early stage in coronary arteries has been associated with low cycle-average wall shear stress magnitude. However, parallel to the identification of an established active role for low wall shear stress in the onset/progression of the atherosclerotic disease, a weak association between lesions localization and low/oscillatory wall shear stress has been observed. In the attempt to fully identify the wall shear stress phenotype triggering early atherosclerosis in coronary arteries, this exploratory study aims at enriching the characterization of wall shear stress emerging features combining correlation-based analysis and complex networks theory with computational hemodynamics. The final goal is the characterization of the spatiotemporal and topological heterogeneity of wall shear stress waveforms along the cardiac cycle. In detail, here time-histories of wall shear stress magnitude and wall shear stress projection along the main flow direction and orthogonal to it (a measure of wall shear stress multidirectionality) are analyzed in a representative dataset of 10 left anterior descending pig coronary artery computational hemodynamics models. Among the main findings, we report that the proposed analysis quantitatively demonstrates that the model-specific inlet flow-rate shapes wall shear stress time-histories. Moreover, it emerges that a combined effect of low wall shear stress magnitude and of the shape of the wall shear stress–based descriptors time-histories could trigger atherosclerosis at its earliest stage. The findings of this work suggest for new experiments to provide a clearer determination of the wall shear stress phenotype which is at the basis of the so-called arterial hemodynamic risk hypothesis in coronary arteries.

The impact of helical flow on coronary atherosclerotic plaque development

BACKGROUND AND AIMS

Atherosclerosis has been associated with near-wall hemodynamics and wall shear stress (WSS). However, the role of coronary intravascular hemodynamics, in particular of the helical flow (HF) patterns that physiologically develop in those arteries, is rarely considered. The purpose of this study was to assess how HF affects coronary plaque initiation and progression, definitively demonstrating its atheroprotective nature.

METHODS

The three main coronary arteries of five adult hypercholesterolemic mini-pigs on a high fat diet were imaged by computed coronary tomography angiography (CCTA) and intravascular ultrasound (IVUS) at 3 (T1, baseline) and 9.4 ± 1.9 (T2) months follow-up. The baseline geometries of imaged coronary arteries (n = 15) were reconstructed, and combined with pig-specific boundary conditions (based on in vivo Doppler blood flow measurements) to perform computational fluid dynamic simulations. Local wall thickness (WT) was measured on IVUS images at T1 and T2, and its temporal changes were assessed. Descriptors of HF and WSS nature were computed for each model, and statistically compared to WT data.

RESULTS

HF intensity was strongly positively associated with WSS magnitude (p < 0.001). Overall, coronary segments exposed to high baseline levels of HF intensity exhibited a significantly lower WT growth (p < 0.05), compared to regions with either mid or low HF intensity.

CONCLUSIONS

This study confirms the physiological significance of HF in coronary arteries, revealing its protective role against atherosclerotic WT growth and its potential in predicting regions undergoing WT development. These findings support future in vivo measurement of coronary HF as atherosclerotic risk marker, overcoming current limitations of in vivo WSS assessment.

Smooth Muscle Cell-Proteoglycan-Lipoprotein Interactions as Drivers of Atherosclerosis

In humans, smooth muscle cells (SMCs) are the main cell type in the artery medial layer, in pre-atherosclerotic diffuse thickening of the intima, and in all stages of atherosclerotic lesion development. SMCs secrete the proteoglycans responsible for the initial binding and retention of atherogenic lipoproteins in the artery intima, with this retention driving foam cell formation and subsequent stages of atherosclerosis. In this chapter we review current knowledge of the extracellular matrix generated by SMCs in medial and intimal arterial layers, their relationship to atherosclerotic lesion development and stabilization, how these findings correlate with mouse models of atherosclerosis, and potential therapies aimed at targeting the SMC matrix-lipoprotein interaction for atherosclerosis prevention.

Endothelial responses to shear stress in atherosclerosis: a novel role for developmental genes

Flowing blood generates a frictional force called shear stress that has major effects on vascular function. Branches and bends of arteries are exposed to complex blood flow patterns that exert low or low oscillatory shear stress, a mechanical environment that promotes vascular dysfunction and atherosclerosis. Conversely, physiologically high shear stress is protective. Endothelial cells are critical sensors of shear stress but the mechanisms by which they decode complex shear stress environments to regulate physiological and pathophysiological responses remain incompletely understood. Several laboratories have advanced this field by integrating specialized shear-stress models with systems biology approaches, including transcriptome, methylome and proteome profiling and functional screening platforms, for unbiased identification of novel mechanosensitive signalling pathways in arteries. In this Review, we describe these studies, which reveal that shear stress regulates diverse processes and demonstrate that multiple pathways classically known to be involved in embryonic development, such as BMP-TGFβ, WNT, Notch, HIF1α, TWIST1 and HOX family genes, are regulated by shear stress in arteries in adults. We propose that mechanical activation of these pathways evolved to orchestrate vascular development but also drives atherosclerosis in low shear stress regions of adult arteries.

Endothelial responses to shear stress in atherosclerosis: a novel role for developmental genes

Flowing blood generates a frictional force called shear stress that has major effects on vascular function. Branches and bends of arteries are exposed to complex blood flow patterns that exert low or low oscillatory shear stress, a mechanical environment that promotes vascular dysfunction and atherosclerosis. Conversely, physiologically high shear stress is protective. Endothelial cells are critical sensors of shear stress but the mechanisms by which they decode complex shear stress environments to regulate physiological and pathophysiological responses remain incompletely understood. Several laboratories have advanced this field by integrating specialized shear-stress models with systems biology approaches, including transcriptome, methylome and proteome profiling and functional screening platforms, for unbiased identification of novel mechanosensitive signalling pathways in arteries. In this Review, we describe these studies, which reveal that shear stress regulates diverse processes and demonstrate that multiple pathways classically known to be involved in embryonic development, such as BMP-TGFβ, WNT, Notch, HIF1α, TWIST1 and HOX family genes, are regulated by shear stress in arteries in adults. We propose that mechanical activation of these pathways evolved to orchestrate vascular development but also drives atherosclerosis in low shear stress regions of adult arteries.

Feasibility and Clinical Significance of In Vivo Cholesterol Crystal Detection Using Optical Coherence Tomography

OBJECTIVE

Cholesterol crystals (CCs) are frequently found at the site of acute myocardial infarctions (AMIs), but the role of CCs in the onset of AMI remains unclear due to the lack of validated in vivo imaging tools. The aim of this study was to validate the ability of optical coherence tomography (OCT) to detect CCs and to compare the prevalence and distribution of CCs in patients with AMIs and stable angina pectoris. Approach and Results: CC assessment using OCT were compared with histopathology results in 45 coronary samples. We investigated 152 consecutive patients with AMIs and 41 patients with single vessel-diseased stable angina pectoris. Based on the presence of plaque ruptures (PR), AMI patients were divided into 2 groups: those with PR (n=112) and those without PR (n=40). CCs invading fibrous caps were defined as superficial-type CCs. A multivariable logistic regression analysis was performed to determine PR predictors. The sensitivity and specificity of OCT for detecting CCs were 68% and 92%, respectively. The prevalence of plaques with CCs was higher in the AMI with PR group (AMI with PR 81%, AMI without PR 48%, stable angina pectoris 39%, P<0.01). A multivariable logistic model showed that superficial-type CCs and thin-cap fibroatheromas were positive predictors for PR.

CONCLUSIONS

OCT has a high specificity and modest sensitivity for the detection of CCs. The combination of CCs invading fibrous cap and thin-cap fibroatheromas detected by OCT may better identify rupture-prone plaques.

Variation in Coronary Atherosclerosis Severity Related to a Distinct LDL (Low-Density Lipoprotein) Profile: Findings From a Familial Hypercholesterolemia Pig Model

OBJECTIVE

In an adult porcine model of familial hypercholesterolemia (FH), coronary plaque development was characterized. To elucidate the underlying mechanisms of the observed inter-individual variation in disease severity, detailed lipoprotein profiles were determined. Approach and Results: FH pigs (3 years old, homozygous LDLR R84C mutation) received an atherogenic diet for 12 months. Coronary atherosclerosis development was monitored using serial invasive imaging and histology. A pronounced difference was observed between mildly diseased pigs which exclusively developed early lesions (maximal plaque burden, 25% [23%-34%]; n=5) and advanced-diseased pigs (n=5) which developed human-like, lumen intruding plaques (maximal plaque burden, 69% [57%-77%]) with large necrotic cores, intraplaque hemorrhage, and calcifications. Advanced-diseased pigs and mildly diseased pigs displayed no differences in conventional risk factors. Additional plasma lipoprotein profiling by size-exclusion chromatography revealed 2 different LDL (low-density lipoprotein) subtypes: regular and larger LDL. Cholesterol, sphingosine-1-phosphate, ceramide, and sphingomyelin levels were determined in these LDL-subfractions using standard laboratory techniques and high-pressure liquid chromatography mass-spectrometry analyses, respectively. At 3 months of diet, regular LDL of advanced-diseased pigs contained relatively more cholesterol (LDL-C; regular/larger LDL-C ratio 1.7 [1.3-1.9] versus 0.8 [0.6-0.9]; P=0.008) than mildly diseased pigs, while larger LDL contained more sphingosine-1-phosphate, ceramides, and sphingomyelins. Larger and regular LDL was also found in plasma of 3 patients with homozygous FH with varying LDL-C ratios.

CONCLUSIONS

In our adult FH pig model, inter-individual differences in atherosclerotic disease severity were directly related to the distribution of cholesterol and sphingolipids over a distinct LDL profile with regular and larger LDL shortly after the diet start. A similar LDL profile was detected in patients with homozygous FH.

Coronary Shear Stress after Implantation of Bioresorbable Scaffolds – a Modern Interdisciplinary Concept at the Border between Interventional Cardiology and Cardiac Imaging

Bioresorbable scaffolds/stents offer new and exciting perspectives in the treatment of patients with acute coronary syndromes, especially after the recent development of invasive imaging techniques, such as optical coherence tomography, which allow complete assessment of vascu-lar segments. A particular advantage of bioresorbable scaffolds is that once the biosorption of the scaffold is complete, the vascular segment regains its normal physiological functions, thus eliminating the risk of late complications. New studies show the importance of shear stress in the progression of vascular atherosclerosis or in accelerating endothelial turnover. Based on the current knowledge in this field, a future standardized determination of shear stress may help in the long-term follow-up of patients that have suffered or are at risk of developing an acute coronary syndrome.

Understanding Vulnerable Plaques: Current Status and Future Directions

The main cause of acute myocardial infarction is plaque rupture accompanied by superimposed coronary thrombosis. Thin-cap fibroatheromas (TCFAs) have been suggested as a type of lesion with a vulnerability that can cause plaque rupture. However, not only the existence of a TCFA but also the fine and complex interactions of other anatomical and hemodynamic factors, such as microcalcification in the fibrous cap, cholesterol crystal-induced inflammasome activation, the apoptosis of intraplaque macrophages, and endothelial shear stress distribution should precede a clinical event caused by plaque rupture. Recent studies are being conducted to identify these mechanisms through molecular imaging and hemodynamic assessment using computational fluid dynamics, which will result in better clinical results through selective coronary interventions.

Evolving understanding of the heterogeneous natural history of individual coronary artery plaques and the role of local endothelial shear stress

PURPOSE OF REVIEW

Anatomic and morphologic features of high-risk coronary plaque have been identified by novel imaging modalities, but it has been less clear which ostensibly high-risk plaques will actually destabilize and cause a new cardiac event. Different plaques with different morphologies coexist within the same artery, but the impact of this heterogeneity on the natural history of coronary artery disease has not been extensively investigated.

RECENT FINDINGS

Coronary plaques exhibit remarkable heterogeneity of local morphological and blood-flow patterns, including endothelial shear stress (ESS), along their longitudinal axis, with important implications for the heterogeneous natural history of coronary disease. The natural history of individual plaques is considerably divergent, with most plaques, even ostensibly high-risk plaques, becoming quiescent and only a minority progressing to destabilize and precipitate a new clinical event. Local areas of proinflammatory low ESS appear to be an important condition for plaque destabilization.

SUMMARY

Characterization of an individual atherosclerotic plaque based on a snapshot of morphological features at a specific location, such as the minimal lumen diameter, may not be sufficiently comprehensive to accurately reflect the risk associated with that plaque. A detailed assessment of both anatomical and functional pathobiologic characteristics in the longitudinal plaque dimension may enhance our understanding of atherosclerosis progression and improve the management of individual patients with coronary artery disease.

Local Low Shear Stress and Endothelial Dysfunction in Patients With Nonobstructive Coronary Atherosclerosis

BACKGROUND

Local hemodynamic factors are important determinants of atherosclerotic plaque development and progression.

OBJECTIVES

The goal of this study was to determine the association between low endothelial shear stress (ESS) and microvascular and epicardial endothelial dysfunction in patients with early atherosclerosis.

METHODS

Sixty-five patients (mean age 52 ± 11 years) with nonobstructive coronary atherosclerosis (luminal diameter stenosis <30%) were included. Microvascular and epicardial coronary endothelial function was assessed by using intracoronary acetylcholine infusion. Vascular profiling, using 2-plane coronary angiography and intravascular ultrasound, was used to reconstruct the three-dimensional anatomy of the left anterior descending artery. Each reconstructed artery was divided into sequential 3-mm segments and analyzed for local ESS with computational fluid dynamics; that is, lower ESS levels at both a 3-mm regional level (average ESS and low ESS) and at a vessel level (lowest ESS per artery) and for plaque characteristics (plaque area, plaque thickness, and plaque burden).

RESULTS

Coronary segments in arteries with abnormal microvascular function exhibited lower ESS compared with segments in arteries with normal microvascular function (average ESS: 1.67 ± 1.04 Pa vs. 2.03 ± 1.72 Pa [p = 0.050]; lowest ESS: 0.54 ± 0.25 Pa vs. 0.72 ± 0.32 Pa [p = 0.014]). Coronary segments in arteries with abnormal epicardial endothelial function also exhibited significantly lower ESS compared with segments in arteries with normal epicardial function (average ESS: 1.49 ± 0.89 Pa vs. 1.93 ± 1.50 Pa [p < 0.0001]; low ESS: 1.26 ± 0.81 Pa vs. 1.56 ± 1.30 Pa [p = 0.001]; lowest ESS: 0.51 ± 0.27 Pa vs. 0.65 ± 0.29 Pa [p = 0.080]). Patients with abnormal microvascular endothelial function exhibited a progressive decrease in average and low ESS, starting from patients with normal epicardial endothelial function to those with both microvascular and epicardial endothelial dysfunction (p < 0.0001 and p = 0.004, respectively).

CONCLUSIONS

These data indicate an association between dysfunction of the microvascular and epicardial endothelium and local ESS at the early stages of coronary atherosclerosis in humans.

MicroRNA regulation of extracellular matrix components in the process of atherosclerotic plaque destabilization

The process of atherosclerotic plaque destabilization, leading to myocardial infarction, is still not fully understood. The pathway - composed of structural and regulatory proteins of the extracellular matrix (ECM) such as collagen, elastin, small leucine-rich proteoglycans, metalloproteinases, cathepsins and serine proteases - is one potential way of atherosclerotic plaque destabilization. The expression of these proteins is controlled by different microRNA molecules. The goal of this paper is to summarize the current investigations and knowledge about ECM in the process of atherosclerotic plaque destabilization, giving special attention to epigenetic expression regulation by microRNA.

Animal models for plaque rupture: a biomechanical assessment

Rupture of atherosclerotic plaques is the main cause of acute cardiovascular events. Animal models of plaque rupture are rare but essential for testing new imaging modalities to enable diagnosis of the patient at risk. Moreover, they enable the design of new treatment strategies to prevent plaque rupture. Several animal models for the study of atherosclerosis are available. Plaque rupture in these models only occurs following severe surgical or pharmaceutical intervention. In the process of plaque rupture, composition, biology and mechanics each play a role, but the latter has been disregarded in many animal studies. The biomechanical environment for atherosclerotic plaques is comprised of two parts, the pressure-induced stress distribution, mainly - but not exclusively – influenced by plaque composition, and the strength distribution throughout the plaque, largely determined by the inflammatory state. This environment differs considerably between humans and most animals, resulting in suboptimal conditions for plaque rupture. In this review we describe the role of the biomechanical environment in plaque rupture and assess this environment in animal models that present with plaque rupture.

Role of Low Endothelial Shear Stress and Plaque Characteristics in the Prediction of Nonculprit Major Adverse Cardiac Events: The PROSPECT Study

OBJECTIVES

This study sought to determine whether low endothelial shear stress (ESS) adds independent prognostication for future major adverse cardiac events (MACE) in coronary lesions in patients with high-risk acute coronary syndrome (ACS) from the United States and Europe.

BACKGROUND

Low ESS is a proinflammatory, proatherogenic stimulus associated with coronary plaque development, progression, and destabilization in human-like animal models and in humans. Previous natural history studies including baseline ESS characterization investigated low-risk patients.

METHODS

In the PROSPECT (Providing Regional Observations to Study Predictors of Events in the Coronary Tree) study, 697 patients with ACS underwent 3-vessel intracoronary imaging. Independent predictors of MACE attributable to untreated nonculprit (nc) coronary lesions during 3.4-year follow-up were large plaque burden (PB), small minimum lumen area (MLA), and thin-cap fibroatheroma (TCFA) morphology. In this analysis, baseline ESS of nc lesions leading to new MACE (nc-MACE lesions) and randomly selected control nc lesions without MACE (nc-non-MACE lesions) were calculated. A propensity score for ESS was constructed for each lesion, and the relationship between ESS and subsequent nc-MACE was examined.

RESULTS

A total of 145 lesions were analyzed in 97 patients: 23 nc-MACE lesions (13 TCFAs, 10 thick-cap fibroatheromas [ThCFAs]), and 122 nc-non-MACE lesions (63 TCFAs, 59 ThCFAs). Low local ESS (<1.3 Pa) was strongly associated with subsequent nc-MACE compared with physiological/high ESS (≥1.3 Pa) (23 of 101 [22.8%]) versus (0 of 44 [0%]). In propensity-adjusted Cox regression, low ESS was strongly associated with MACE (hazard ratio: 4.34; 95% confidence interval: 1.89 to 10.00; p < 0.001). Categorizing plaques by anatomic risk (high risk: ≥2 high-risk characteristics PB ≥70%, MLA ≤4 mm2, or TCFA), high anatomic risk, and low ESS were prognostically synergistic: 3-year nc-MACE rates were 52.1% versus 14.4% versus 0.0% in high-anatomic risk/low-ESS, low-anatomic risk/low-ESS, and physiological/high-ESS lesions, respectively (p < 0.0001). No lesion without low ESS led to nc-MACE during follow-up, regardless of PB, MLA, or lesion phenotype at baseline.

CONCLUSIONS

Local low ESS provides incremental risk stratification of untreated coronary lesions in high-risk patients, beyond measures of PB, MLA, and morphology.

Temporal and spatial changes in wall shear stress during atherosclerotic plaque progression in mice

Wall shear stress (WSS) is involved in atherosclerotic plaque initiation, yet its role in plaque progression remains unclear. We aimed to study (i) the temporal and spatial changes in WSS over a growing plaque and (ii) the correlation between WSS and plaque composition, using animal-specific data in an atherosclerotic mouse model. Tapered casts were placed around the right common carotid arteries (RCCA) of ApoE^-/- mice. At 5, 7 and 9 weeks after cast placement, RCCA geometry was reconstructed using contrast-enhanced micro-CT. Lumen narrowing was observed in all mice, indicating the progression of a lumen intruding plaque. Next, we determined the flow rate in the RCCA of each mouse using Doppler Ultrasound and computed WSS at all time points. Over time, as the plaque developed and further intruded into the lumen, absolute WSS significantly decreased. Finally at week 9, plaque composition was histologically characterized. The proximal part of the plaque was small and eccentric, exposed to relatively lower WSS. Close to the cast a larger and concentric plaque was present, exposed to relatively higher WSS. Lower WSS was significantly correlated to the accumulation of macrophages in the eccentric plaque. When pooling data of all animals, correlation between WSS and plaque composition was weak and no longer statistically significant. In conclusion, our data showed that in our mouse model absolute WSS strikingly decreased during disease progression, which was significantly correlated to plaque area and macrophage content. Besides, our study demonstrates the necessity to analyse individual animals and plaques when studying correlations between WSS and plaque composition.

Sex Differences in the Coronary System

Cardiovascular disease remains the leading cause of morbidity and mortality for both women and men. Emerging evidence supports that ischemic heart disease (IHD) may manifest differently in women and men, in ways ranging from the clinical presentation, diagnosis, and management of disease to the basic biology and biomechanics of cardiomyocyte function and the coronary circulation. Women consistently present with a higher burden of symptoms and comorbidities as compared with men and experience worse outcomes. These data have proved perplexing given the decreased likelihood of women to demonstrate obstructive coronary artery disease (CAD) on coronary angiography. Reported sex differences have long been influenced by the practice of defining heart disease primarily as obstructive CAD, but obstructive plaque is now recognized as neither necessary nor sufficient to explain symptoms of IHD, and it is no longer adequate to tailor diagnostic and treatment strategies only to this subset of patients. To date, women remain underrepresented in guideline-changing heart disease research and trials, creating important limitations in the evidence base for cardiovascular medicine. Smaller epicardial coronary arteries in women as compared to men, coupled with differences in shear stress and inflammatory mediators over the life span, may modify the development of CAD in susceptible patients into a diffuse pattern with more contribution from coronary vasomotor dysfunction than focal obstruction. Newer studies corroborate that symptomatic women are more likely than men to present with nonobstructive CAD and coronary microvascular dysfunction. When present, these processes increase cardiovascular risk in both women and men but may constitute an especially malignant phenotype in a subset of severely affected women, with implications for the management of not only CAD but also heart failure with preserved ejection fraction. This represents a state-of-the-art review of sex differences in the coronary system, with an eye toward how diverse pathophysiological processes may contribute to IHD phenotypes prevalent in women and men. Beyond providing women and men with equitable optimal care according to current paradigms, understanding the pathophysiology of IHD beyond a conventional focus on obstructive CAD is needed to address what is likely a combination of biological as well as environmental determinants of their prognosis.