Properties Of Vascular Wall Research Articles

Uncertainty Quantification in the In Vivo Image-Based Estimation of Local Elastic Properties of Vascular Walls.

Patient-specific computational models are a powerful tool for planning cardiovascular interventions. However, the in vivo patient-specific mechanical properties of vessels represent a major source of uncertainty. In this study, we investigated the effect of uncertainty in the elastic module (E) on a Fluid-Structure Interaction (FSI) model of a patient-specific aorta. The image-based χ-method was used to compute the initial E value of the vascular wall. The uncertainty quantification was carried out using the generalized Polynomial Chaos (gPC) expansion technique. The stochastic analysis was based on four deterministic simulations considering four quadrature points. A deviation of about ±20% on the estimation of the E value was assumed. The influence of the uncertain E parameter was evaluated along the cardiac cycle on area and flow variations extracted from five cross-sections of the aortic FSI model. Results of stochastic analysis showed the impact of E in the ascending aorta while an insignificant effect was observed in the descending tract. This study demonstrated the importance of the image-based methodology for inferring E, highlighting the feasibility of retrieving useful additional data and enhancing the reliability of in silico models in clinical practice.

Changes of Aortic Tissue MicroRNA/mRNA Expression in Patients with Long-Term Left Ventricular Assist Device

Purpose Attenuation of physiological pulsatility after continuous flow left ventricular assist device (LVAD) implantation has been reported as a contributor to alteration of aortic wall morphology and function. MicroRNAs are non-coding RNAs that act to regulate translation of messenger RNA (mRNA) into proteins and are fine-tuners of gene expression in response to pathophysiological stimuli. Differences in gene expression (mRNA) and in post-transcriptional regulators (microRNAs) could reflect biological response to exposure to the low pulsatile environment. We hypothesized that pulsatility deficit caused by LVAD may influence miRNA/mRNA expression in aortic tissue. The aim of the study was to detect miRNA/mRNA associations in the aortic tissue during LVAD support. Methods Aortic samples were collected at the time of LVAD implant and at heart transplantation in 16 patients (mean age 49.6±16.8 years; 3 females) and examined for miRNA/mRNA profiling. QuantSeq 3′ mRNA-Sequencing was used to examine differences in gene expression. Using human miRNome panels a profile of 752 miRNAs was identified. Results A total of 277 mRNAs were dysregulated after LVAD support (padj Conclusion The study provides additional insight in pathophysiology of vascular changes after LVAD implantation. A significant regulation of mRNAs involved in ECM and collagen fibers organization in response to implantation of LVAD was observed, which may suggest infliction of ECM homeostasis resulting in changes of intrinsic properties of vascular wall and arterial stiffness. Downregulation of miRNAs involved in molecular processes related to immune response, could implicate dysregulation in inflammatory processes after LVAD implantation.

Implications of diesel exhaust fumes exposure on vascular wall properties, endothelial function and inflammatory process

Background and Aims: Diesel exhaust fumes are toxic compounds, whose acute effects on the cardiovascular system are well known. However, their short term impact has not been thoroughly studied. Aim: Study acute and short-term (24 h) effects of diesel exhaust particles (DEPs) on endothelial function, vascular wall properties, inflammation and coagulation.

Capabilities of photoplethysmography as a method for screening of cardiovascular system pathology

Currently, vegetative dysfunction considered to be one of principal mechanisms in the pathogenesis of cardiovascular pathology, which causes a cascade of events leading to changes in the properties and a structure of vascular wall. This review article contains literature from various databases (Russian science citation index, PubMed, Google Shcolar, Scopus). It presents the methods for assessing vegetative imbalance. In particular, the method of photoplethysmography (PPGV) is considered for recording periodic fluctuations at various frequencies in the distal vascular bed which characterize physiological processes (cardiac activity, respiratory influences, neurogenic, myogenic and endothelial activity). In addition, other diagnostic capabilities of PPGV such as heart rate (HR) assessment, determining the properties of vascular wall and the level of blood saturation are elucidated. This paper demonstrates a wide range of PPGV applications. The simplicity of PPGV reproduction and its cost-effectiveness make it feasible both in routine clinical practice for the purposes of screening for cardiovascular pathology, and for individual health monitoring incorporated in smart devices.

Acute exposure to diesel affects inflammation and vascular function.

Diesel exhaust fumes represent one of the most common toxic pollutants. The prolonged effects of acute exposure to this pollutant on inflammatory status and vascular properties are unknown. During a 2-h session, 40 healthy subjects were exposed to diesel exhaust fumes and/or filtered air. Endothelial function was assessed with flow mediated dilation, arterial stiffness with pulse wave velocity and reflected waves with augmentation index. C-reactive protein, fibrinogen, protein C levels and protein S activity were also measured. Standard deviation of normal to normal R-R intervals (SDNN) was used to assess heart rate variability. Measurements were assessed before exposure and 2 and 24 h after diesel exposure. Compared with filtered air, exposure to diesel exhaust fumes decreased flow mediated dilation and increased pulse wave velocity and augmentation index up to 24 h after the exposure (p < 0.001 for all). Similarly, compared with filtered air, diesel exhaust exposure impaired SDNN during the 24-h study period (p = 0.007). C-reactive protein and fibrinogen levels were significantly increased after diesel exhaust exposure while protein C levels and protein S activity decreased (p < 0.01 for all). Exposure to diesel exhaust fumes resulted in higher C-reactive protein concentration in smokers compared with non-smokers (p < 0.001). Short-term exposure to diesel exhaust fumes has a prolonged adverse impact on endothelial function and vascular wall properties, along with impaired heart rate variability, abnormal fibrinolytic activity and increased markers of inflammation. These findings give insights into the mechanisms underlining the increased cardiovascular risk of subjects regularly exposed to diesel exhaust fumes.

Features of the immune response and vascular wall stiffness in workers exposed to industrial aerosols

Introduction. In recent years, in occupational pathology, much attention is paid to professionally caused diseases, a special place among which is occupied by cardiovascular pathology. Vascular wall stiff ness is considered as an independent cardiovascular risk factor. This makes it important to study the mechanism of development of arterial stiffness, a key component of which is inflammation.The aim of the study was to identify the relationship between immune parameters and vascular wall stiff ness according to volumetric sphygmography in workers exposed to industrial aerosols.Materials and methods. A survey was conducted of 55 men working in conditions of exposure to industrial aerosols, and 32 men who do not have professional contact with industrial pollutants. Serum concentrations of class A and G immunoglobulins, cytokines, tumor necrosis factor α, and C-reactive protein were determined by solid-phase enzyme immunoassay. Assessment of elastic properties of the vascular wall was carried out by volumetric sphygmography.Results. Increased production of anti-inflammatory interleukin–8, immunoglobulin G and C-reactive protein, as well as increased cardiovascular and ankle vascular index on the right and left in the group working under the influence of industrial aerosols was found. Median concentrations of immunoglobulins, interleukins and C-reactive protein were independent of changes in the value of the cardiovascular ankle vascular index. Increased rigidity of the vascular wall was accompanied by an increase in the production of tumor necrosis factor α. Thus, in the group of persons with increased stiff ness, the level of this cytokine was 3 times higher than in the group of persons with normal values of the cardiovascular-ankle vascular index. The relationship between the cardiovascular ankle vascular index and the concentration of tumor necrosis factor α (r=0.61; p=0.009), C-reactive protein (r=0.54; p=0.02) and feedback with the level of anti-infl ammatory interleukin–10 (r=0.36; p=0.04) was revealed.Conclusions. The established significant correlations between cytokines (tumor necrosis factor α, interleukin–10), C-reactive protein and individual indicators of volumetric sphygmography (cardio-ankle vascular index) indicate the pathogenetic role of cytokines and acute phase proteins in the violation of elastic properties of the vascular bed in workers under the influence of industrial aerosols.

PP.18.07] RELATIONSHIP OF ELASTIC VASCULAR WALL PROPERTIES, RENAL FUNCTION AND INFLAMMATORY BIOCHEMICAL MARKERS IN HYPERTENSIVE PATIENTS WITH METABOLIC DISORDERS

Objective: To study the elastic properties of vascular wall, 24-hour blood pressure (BP) profile, parameters of renal function, biochemical parameters and their relationship with metabolic disorders in patients with arterial hypertension (AH) and metabolic disorders (abdominal obesity and dyslipidemia). Design and method: 130 patients (mean age 47.20 ± 9.6 years) were divided into 2 groups. The main group (group 1) included 77 subjects with AH degree I-III and MD (mass body index (MBI) 34.5 ± 3.9 kg/m2) and the control group (group 2) contained 53 subjects with AH without MD. The parameters of 24-hour BP monitoring, sphygmography, renal function (microalbuminuria, creatinine and estimation glomerular filtration rate (eGFR) using MDRD formule), parameters of the lipid profile, inflammatory markers – homocysteine, C-reactive protein (hs-CRP) and fibrinogen were estimated. Results: In group 1 there was registered significant increase in mean 24-hour and daytime systolic BP (SBP), time and square indices, in night time SBP and diastolic BP variability (p < 0.001); in sphygmography indices (cardio-ankle vascular index (CAVI), pulse wave velocity (PVW) and anklebrachial index (ABI) (p < 0.01); in parameters of renal function - microalbuminuria and eGFR (p < 0.001); in biochemical parameters - total cholesterol, fibrinogen (p < 0.016) and hs-CRP level (p = 0.04) compared to group 2. In group 1 correlation analysis revealed a positive correlation between microalbuminuria and PWV-R (p = 0.039), creatinine and R-ABI (p = 0.007), eGFR and L-ABI (p = 0.05), hs-CRP and CAVI and between fibrinogen and eGFR (p < 0.05). Besides, regression analysis method in patients with AH degree I revealed a positive relationship of creatinine with PWV-L (R2 = 0.14, p = 0.03), in patients with AH degree II - creatinine with CAVI and MBI (R2 = 0.451, p = 0.004 and p = 0.012). Conclusions: The relationship between elastic parameters of vascular wall, inflammatory markers, parameters of renal function and MBI has a pathogenetic basis for the progression of hypertension and impaired function of the target organ.

Characteristic of Elastic Properties of The Vascular Wall During Treatment of Hypertension

Characteristic of Elastic Properties of The Vascular Wall During Treatment of Hypertension

Renin-Angiotensin-Aldosterone System Is Not Involved in the Arterial Stiffening Induced by Acute and Prolonged Exposure to High Altitude.

URL: https://www.clinicaltrialsregister.eu/. Unique identifier: 2008-000540-14.

A comparison of the material properties of natural and synthetic vascular walls

Characterization of the mechanical properties of native and synthetic vascular grafts is an essential task in the process of designing novel vascular constructs. The aim in this study was to compare the mechanical behavior of ovine left Subclavian artery with that of POSS-PCU (a commercial biomaterial which is currently under clinical investigation. ClinicalTrials.gov Identifier: NCT02301312). We used Delfino's strain energy potential within the framework of quasilinear viscoelasticity theory to capture the viscoelastic response of the considered materials. The material parameters of the quasilinear viscoelastic constitutive equation were determined through a combination of experimental and computational method. First, a uniaxial tensile testing device was used to perform a series of stress relaxation tests on ring samples. Then, the derived quasilinear viscoelastic models were implemented into finite element system. With the aid of mechanical experimentation and finite element simulation, the material parameters were obtained, modified and used for comparison of the mechanical properties of vascular walls. The results showed that the stiffness and the long term viscoelastic parameters of POSS-PCU may lead to different stress responses of the vascular walls. These two factors can be improved by modifications in manufacturing parameters of the synthetic vessel.

The effect of an acute bout of resistance exercise on carotid artery strain and strain rate.

Arterial wall mechanics likely play an integral role in arterial responses to acute physiological stress. Therefore, this study aimed to determine the impact of low and moderate intensity double‐leg press exercise on common carotid artery (CCA) wall mechanics using 2D vascular strain imaging. Short‐axis CCA ultrasound images were collected in 15 healthy men (age: 21 ± 3 years; stature: 176.5 ± 6.2 cm; body mass; 80.6 ± 15.3 kg) before, during, and immediately after short‐duration isometric double‐leg press exercise at 30% and 60% of participants' one‐repetition maximum (1RM: 317 ± 72 kg). Images were analyzed for peak circumferential strain (PCS), peak systolic and diastolic strain rate (S‐SR and D‐SR), and arterial diameter. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP) were simultaneously assessed and arterial stiffness indices were calculated post hoc. A two‐way repeated measures ANOVA revealed that during isometric contraction, PCS and S‐SR decreased significantly (P < 0.01) before increasing significantly above resting levels post exercise (P < 0.05 and P < 0.01, respectively). Conversely, D‐SR was unaltered throughout the protocol (P = 0.25). No significant differences were observed between the 30% and 60% 1RM trials. Multiple regression analysis highlighted that HR, BP, and arterial diameter did not fully explain the total variance in PCS, S‐SR, and D‐SR. Acute double‐leg press exercise is therefore associated with similar transient changes in CCA wall mechanics at low and moderate intensities. CCA wall mechanics likely provide additional insight into localized intrinsic vascular wall properties beyond current measures of arterial stiffness.

Circadian CLOCK Gene Variants, Parameters of Arterial Stiffness and Blood Pressure Levels in Subjects Without Arterial Hypertension

CLOCK gene polymorphic variants, parameters of arterial stiffness and blood pressure (BP) variability were studied in 115 normotensive Russian patients without cardiovascular diseases (62 men, 53 women; mean age 36.4+/-1.01 years). Examination included ECG, 24h BP monitoring, duplex scan of carotid arteries, registration of vascular stiffness parameters, and genotyping of the following polymorphic markers of CLOCK: 3111T>C (3-untranslated region), 862T>C (exon 9) and 257T>G (promoter region) by PCR-RFLP method. Pulse wave velocity was not significantly different among carriers of various 257T>G, 862T>C, 3111T>C genotypes. Augmentation index (Aix night, Aix max) values were lower in individuals with genotypes allegedly associated with essential hypertension and ischemic heart disease (257GG, 862CC, 3111CC). Arterial stiffness index (ASI) was significantly higher in men having CC genotype of 862T>C. Polymorphic variants 257T>G and 862T>C SNPs of CLOCK gene were found to be associated with parameters reflecting BP variability (morning rise of diastolic BP and rate of BP rise). These results provide a basis for suggestion that the CLOCK gene polymorphism is one of factors determining elastic properties of vascular wall. The suggestion is supported by discussion of possible molecular mechanisms of circadian genes impact on elasticity and rigidity of vessel.

Detailed Measurement of Wall Strain with 3D Speckle Tracking in the Aortic Root: A Case of Bionic Support for Clinical Decision Making

Three-dimensional (3D) wall motion tracking (WMT) based on ultrasound imaging enables estimation of aortic wall motion and deformation. It provides insights into changes in vascular compliance and vessel wall properties essential for understanding the pathogenesis and progression of aortic diseases. In this report, we employed the novel 3D WMT analysis on the ascending aorta aneurysm (AA) to estimate local aortic wall motion and strain in case of a patient scheduled for replacement of the aortic root. Although progression of the diameter indicates surgical therapy, at present we addressed the question for optimal surgical time point. According to the data, AA in our case has enlarged diameter and subsequent reduced circumferential wall strain, but area tracking data reveals almost normal elastic properties. Virtual remodeling of the aortic root opens a play list for different loading conditions to determine optimal surgical intervention in time.

Relationship of Vascular Factors on Electrophysiologic Severity of Diabetic Neuropathy.

ObjectiveTo investigate the impact of vascular factors on the electrophysiologic severity of diabetic neuropathy (DPN).MethodsTotal 530 patients with type 2 diabetes were enrolled retrospectively. We rated severity of DPN from 1 (normal) to 4 (severe) based on electrophysiologic findings. We collected the data concerning vascular factors (including brachial-ankle pulse wave velocity [PWV], ankle brachial index, ultrasound of carotid artery, lipid profile from the blood test, and microalbuminuria [MU] within 24 hours urine), and metabolic factors of diabetes (such as glycated hemoglobin [HbA1c]). We analyzed the differences among the four subgroups using χ2 test and ANOVA, and ordinal logistic regression analysis was performed to investigate the relationship between significant variables and severity of DPN.ResultsThe severity of DPN was significantly associated with duration of diabetes, HbA1c, existence of diabetic retinopathy and nephropathy, PWV, presence of plaque, low density lipoprotein-cholesterol and MU (p<0.05). Among these variables, HbA1c and presence of plaque were more significantly related with severity of DPN in logistic regression analysis (p<0.001), and presence of plaque showed the highest odds ratio (OR=2.52).ConclusionOur results suggest that markers for vascular wall properties, such as PWV and presence of plaque, are significantly associated with the severity of DPN. The presence of plaque was more strongly associated with the severity of DPN than other variables.

Biomechanical model of cerebral vascular dynamics and their effect on CSF dynamics

With advancing age venous wall thickness increases going along with a loss of elastic properties, the arterioles curl and capillary density decreases leading to a reduction of cross sectional area [1]. Even in healthy individuals these changes influence vascular and CSF dynamics, as a reduction of total cerebral blood flow, aqueduct and cervical stroke volume are reported [2]. In NPH these dynamics seem to be altered in a different way, as aqueduct stroke volume [2] and ICP amplitude are increased and arteriovenous delay is drastically reduced compared to normal aging [3]. However it is not clear in what way the described vascular alterations influence the pressure propagation inside the vessels and impact CSF dynamics. So far no biomechanical model exists that investigates the influence of macroscopic and microscopic changes of cerebral blood vessels. That is why we put a model up for discussion that simulates vascular pressure propagation and enables the investigation of altered vascular properties in the context of NPH. A Matlab Simulink model was developed reproducing each vessel section by a distensible compartment. Therefore the cerebral vascular tree was divided into 13 sections from carotid artery to venous sinuses and the pulsatile carotid artery and sinus pressure were inputted as Fourier series. The cross sectional area was varied according to literature data and flow resistance was implemented taking into account the rheological characteristics of blood. The Windkessel function and relaxation properties of vascular walls were integrated by a Voigt model, enabling the variation of wall properties for each section individually. Due to the distensible vessel walls each section interacts with the CSF compartment and autoregulation was implemented by a simple proportional controller. After parameterisation mean pressure and pressure amplitude in the vessel sections showed good accordance with literature values [4]. We have proposed a model of vascular dynamics that is able to identify the impact of altered vascular wall properties and structural changes. Furthermore the effect of different arterial and venous input pressure profiles can be analysed. These parameter analyses are part of our ongoing research.

Three-dimensional human arterial wall models for in vitro permeability assessment of drug and nanocarriers

Monolayers of endothelial cells (1L-ECs) have been generally used as in vitro vascular wall models to study the vascular mechanisms and transport of substances. However, these two-dimensional (2D-) system cannot represent the properties of native vascular walls which have a 3D-structure and are composed of not only ECs, but also smooth muscle cells (SMCs) and other surrounding tissues. Here in, 5-layered (5L) 3D-arterial wall models (5L-AWMs) composed of EC monolayer and 4-layered SMCs were constructed by hierarchical cell manipulation. We applied the 5L-AWMs to evaluate their barrier function and permeability to nano-materials in order to analyze drug, or drug nanocarrier permeability to the blood vessel in vitro. Barrier property of the 3D-AWMs was confirmed by Zonula occludens (ZO-1) staining and their transendothelial electrical resistance (TEER), which was comparable to 1L-ECs, while the SMCs showed close to zero. The effect of substance size to permeability across the 5L-AWMs was clearly observed from dextrans with various molecular weights, which agreed well with the known phenomena of the in vivo blood vessels. Importantly, transport of nano-materials could be observed across the depth of 5L-AWMs, suggesting the advantage of 3D-AWMs over general 2D-systems. By using this system, we evaluate the transport of 35nm phenylalanine-modified poly(γ-Glutamic Acid) nanoparticles (γ-PGA-Phe NPs) as a candidate of biodegradable drug carrier. Interestingly, despite of having comparable size to dextran-2000k (28nm), the γ-PGA-Phe NPs distinctly showed approximately 20 times faster transport across the 5L-AWMs, suggesting the effect of intrinsic properties of the substance on the transport. This in vitro evaluation system using the 3D-AWMs is therefore useful for the design and development of nano-drug carriers for treatment of vascular diseases, such as atherosclerosis.

FRI0277 Arterial stiffness in systemic lupus erythematosus (SLE) patients: a controlled study

BackgroundArterial stiffness reflects changes in mechanical properties of vascular wall that occurs early with onset of vascular disease and may be a reliable surrogate marker for cardiovascular disease (CVD) in...

Transmission of pulsatility in the microcirculation: Where and how damping occurs?

BackgroundPulsatility of blood flow plays a critical role in vascular regulation. It is prominent in arterioles but attenuated in venules, due to damping in microvascular beds. However, the damping mechanisms of flow pulsatility in microcirculation remain unclear.MethodsTo explore the damping process, we developed a mathematical model describing pulse propagation and reflection through vascular network and applied it to artificial test networks with defined properties and a mesenteric experimental network (546 segments). Pulse damping was quantified by percent change in pulsatility index (PI, pressure amplitude/mean pressure).ResultsIn passage through experimental and test networks, PI is reduced by about 30%. Possible damping mechanisms were investigated by changing modeling parameters and properties of test networks. PI damping was not affected by eliminating viscous properties of vascular wall. Upon eliminating wave reflection related to output boundaries, bifurcations, and to vascular resistance, PI damping was reduced to 27, 18, and 2%, respectively.ConclusionDamping related to vascular resistance dominates in the microcirculation and is mostly related to wave reflection. (supported by National Nature Science Foundation of China, # 81271662).

Comparative in vivo and in vitro postmortem ultrasound assessment of intima-media thickness with additional histological analysis in human carotid arteries

Summary The present study aims to validate the technique of in vitro ultrasonography (US) by comparative analysis of premortem intima–media thickness (IMT), postmortem IMT and average wall thickness. In vivo common carotid artery (CCA) IMT was measured bilaterally in 25 patients at 30 mm proximal from the flow divider. After autopsy in vitro US was performed and postmortem IMT was measured at the same level. Snap frozen arterial specimens were processed for average wall thickness determination and for histology. High degree of correlation was found between in vivo IMT, in vitro IMT and average wall thickness. Our results demonstrate: (1) in vitro US is a reliable and reproducible tool for the examination of autopsied arterial specimens to obtain valuable information about vascular wall properties and to identify the optimal vascular segment for tissue sampling; (2) snap freezing and cryosectioning of in toto excised arterial specimens is recommended for comparative histological–US studies.

Measurement of aortic wall strain with 3D speckle tracking*

Aims: Non-invasive ultrasound coupled with speckle tracking may estimate aortic wall motion and deformation providing important insight into changes in vascular compliance and vessel wall properties which are necessary for understanding the pathogenesis and progression of aortic diseases, such as atherosclerosis and aneurysm. So far, 2D speckle tracking has been used in arterial wall strain measurement. In this study, the novel 3D speckle tracking technique was employed to estimate aortic wall motion and strain.