Arterial Wall Compliance Research Articles

Frequency domain analysis of photoplethysmographic and arterial pressure waveforms for assessing hemodynamics in children with congenital heart surgery.

Time-domain parameters are less reliable in children due to increased arterial and chest wall compliance. We assessed the ability of indices derived from frequency analysis of photoplethysmography (PPG) and arterial blood pressure (ABP) waveforms to predict the hemodynamic state in children undergoing congenital heart surgery. We analyzed waveforms after cardiopulmonary bypass period in 76 children who underwent total repair of congenital heart disease. Amplitude density of baseline and amplitude modulation in PPG and ABP by respiratory frequency were obtained using fast Fourier transform analysis and normalized by cardiac pulse height (representing respiratory modulations in venous blood [PPG-DC%] and in amplitude [PPG-AC%] at respiratory frequency). The ratio of amplitude density of PPG at the cardiac frequency (CF) to ABP-CF was used to assess vascular compliance. We assessed volume replacement (ml/kg) and vasoactive inotropic score (VIS). Children requiring volume replacement > 10 ml/kg (15.8%) showed higher PPG-DC% than those not requiring it (median: 52.4%, 95% CI [24.8, 295.1] vs. 36.7% [10.7, 125.7], P = 0.017). In addition, children with a VIS > 7 (22.4%) showed higher PPG-CF/ABP-CF (3.6 [0.91, 10.8] vs. 1.2 [0.27, 5.5], P = 0.008). On receiver operating characteristic curve analysis, PPG-DC% predicted a higher fluid requirement (area under the curve: 0.71, 95% CI [0.604, 0.816], P = 0.009), while PPG-CF/ABP-CF predicted a higher VIS (0.714, [0.599, 0.812], P = 0.004). Frequency domain analysis of PPG and ABP may assess hemodynamic status requiring fluid or vasoactive inotropic therapy after congenital heart surgery.

Drivers of vascular growth and remodeling: A computational framework to promote benign adaptation in the Ross procedure

In the sixties, Dr Donald Ross designed a surgical solution for young patients with aortic valve disease by using the patients’ own pulmonary valve. The Ross procedure is the only aortic valve replacement technique that can restore long-term survival and preserve quality of life. The main failure mode of the Ross procedure is wall dilatation, potentially leading to valve regurgitation and leakage. Dilatation occurs due to the inability of the pulmonary autograft to adapt to the sudden increase in loading when exposing to aortic pressures. Previous experimental data has shown that a permanent external support wrapped around the artery can prevent the acute dilatation of the arterial wall. However, the textile support leads to stress-shielding phenomena due to the loss of mechanical wall compliance. We present a pragmatic and modular computational framework of arterial growth and remodeling predicting the long-term outcomes of cardiovascular tissue adaptation, with and without textile wrapping. The model integrates mean, systolic and diastolic pressures and assumes the resulting wall stresses to drive the biological remodeling rules. Rather than a single mean pressure or stress deviation from the homeostatic state, we demonstrate that only pulsatile stresses can predict available experimental results. Therefore, we suggest that a biodegradable external support could induce benign remodeling in the Ross procedure. Indeed, a biodegradable textile wrapped around the autograft fulfills the trade-off between prevention of acute dilatation on the one hand and recovery of arterial wall compliance on the other hand. After further validation, the computational framework can set the basis for the development of an actual biodegradable external support for the Ross procedure with optimized polymer mechanical properties and degradation behavior.

Fluid-structure interactions of peripheral arteries using a coupled in silico and in vitro approach

Vascular compliance is considered both a cause and a consequence of cardiovascular disease and a significant factor in the mid- and long-term patency of vascular grafts. However, the biomechanical effects of localised changes in compliance cannot be satisfactorily studied with the available medical imaging technologies or surgical simulation materials. To address this unmet need, we developed a coupled silico-vitro platform which allows for the validation of numerical fluid-structure interaction results as a numerical model and physical prototype. This numerical one-way and two-way fluid-structure interaction study is based on a three-dimensional computer model of an idealised femoral artery which is validated against patient measurements derived from the literature. The numerical results are then compared with experimental values collected from compliant arterial phantoms via direct pressurisation and ring tensile testing. Phantoms within a compliance range of 1.4–68.0%/100 mmHg were fabricated via additive manufacturing and silicone casting, then mechanically characterised via ring tensile testing and optical analysis under direct pressurisation with moderately statistically significant differences in measured compliance ranging between 10 and 20% for the two methods. One-way fluid-structure interaction coupling underestimated arterial wall compliance by up to 14.7% compared with two-way coupled models. Overall, Solaris™ (Smooth-On) matched the compliance range of the numerical and in vivo patient models most closely out of the tested silicone materials. Our approach is promising for vascular applications where mechanical compliance is especially important, such as the study of diseases which commonly affect arterial wall stiffness, such as atherosclerosis, and the model-based design, surgical training, and optimisation of vascular prostheses.

The effects of cardiorespiratory fitness and ageing on arterial stiffness in athletic older populations

Introduction: Arterial stiffening is a physiological occurrence where there is a decrease in arterial wall compliance, which alters blood pressure and flow. This causes significant aetiological consequences such as hypertension and cardiovascular events, and, as such, arterial stiffness can be used as a subclinical marker for cardiovascular disease. Importantly, arterial stiffness increases in parallel with ageing, even in the absence of disease, thus the prevention of arterial stiffening is of considerable clinical importance for reducing cardiovascular morbidity and mortality.

Hemodynamic Parameters After Prone Positioning of COVID-19 Patients

Aim of the study. To examine the effect of prone positioning on hemodynamics in patients with COVID-19.Materials and methods. The study enrolled 84 patients of both sexes with community-acquired multisegmental viral and bacterial pneumonia associated with COVID-19, who were divided into groups according to the type of respiratory support. The tests were performed using the integrated hardware and software system for noninvasive central hemodynamic assessment by volumetric compression oscillometry.Results. We found that the pulse blood pressure velocity decreased from 281 [242.0; 314.0] to 252 [209; 304] mm Hg/s in patients with severe COVID-19 on oxygen support (p=0.005); volume ejection rate decreased from 251 [200; 294] to 226 [186; 260] ml/s (P=0.03); actual/estimated normalized vascular resistance ratio dropped from 0.549 [0.400; 0.700] to 0.450 [0.300; 0.600] (P=0.002), while the arterial wall compliance increased from 1.37 [1.28; 1.67] to 1.45[1.10; 1.60] ml/mm Hg (P=0.009). Prone positioning of patients on noninvasive lung ventilation associated with a reduction of linear blood flow rate from 40.0 [34.0; 42.0] to 42.5 [42.5; 47.25] cm/s (7=0.04) and arterial wall compliance from 1.4 [1.24; 1.50] to 1.32 [1.14; 1.49] ml/mm Hg (7=0.03). Prone positioning of patients on invasive lung ventilation did not result in significant hemodynamic changes.Conclusion. The greatest hemodynamic changes during prone positioning were found in patients on oxygen respiratory support, whereas the least significant alterations were seen in patients on invasive ventilatory support.

Numerical modeling in arterial hemodynamics incorporating fluid-structure interaction and microcirculation

BackgroundThe effects of arterial wall compliance on blood flow have been revealed using fluid-structure interaction in last decades. However, microcirculation is not considered in previous researches. In fact, microcirculation plays a key role in regulating blood flow. Therefore, it is very necessary to involve microcirculation in arterial hemodynamics.ObjectiveThe main purpose of the present study is to investigate how wall compliance affects the flow characteristics and to establish the comparisons of these flow variables with rigid wall when microcirculation is considered.MethodsWe present numerical modeling in arterial hemodynamics incorporating fluid-structure interaction and microcirculation. A novel outlet boundary condition is employed to prescribe microcirculation in an idealised model.ResultsThe novel finding in this work is that wall compliance under the consideration of microcirculation leads to the increase of wall shear stress in contrast to rigid wall, contrary to the traditional result that wall compliance makes wall shear stress decrease when a constant or time dependent pressure is specified at an outlet.ConclusionsThis work provides the valuable study of hemodynamics under physiological and realistic boundary conditions and proves that wall compliance may have a positive impact on wall shear stress based on this model. This methodology in this paper could be used in real model simulations.

Defective autophagy in vascular smooth muscle cells increases passive stiffness of the mouse aortic vessel wall.

Aging and associated progressive arterial stiffening are both important predictors for the development of cardiovascular diseases. Recent evidence showed that autophagy, a catabolic cellular mechanism responsible for nutrient recycling, plays a major role in the physiology of vascular cells such as endothelial cells and vascular smooth muscle cells (VSMCs). Moreover, several autophagy inducing compounds are effective in treating arterial stiffness. Yet, a direct link between VSMC autophagy and arterial stiffness remains largely unidentified. Therefore, we investigated the effects of a VSMC-specific deletion of the essential autophagy-related gene Atg7 in young mice (3.5months) (Atg7F/F SM22α-Cre+ mice) on the biomechanical properties of the aorta, using an in-house developed Rodent Oscillatory Tension Set-up to study Arterial Compliance (ROTSAC). Aortic segments of Atg7F/F SM22α-Cre+ mice displayed attenuated compliance and higher arterial stiffness, which was more evident at higher distention pressures. Passive aortic wall remodeling, rather than differences in VSMC tone, is responsible for these phenomena, since differences in compliance and stiffness between Atg7+/+ SM22α-Cre+ and Atg7F/F SM22α-Cre+ aortas were more pronounced when VSMCs were completely relaxed by the addition of exogenous nitric oxide. These observations are supported by histological data showing a 13% increase in medial wall thickness and a 14% decrease in elastin along with elevated elastin fragmentation. In addition, expression of the calcium-binding protein S100A4, which is linked to matrix remodeling, was elevated in aortic segments of Atg7F/F SM22α-Cre+ mice. Overall, these findings illustrate that autophagy exerts a crucial role in defining arterial wall compliance.

The value of non-invasive vascular elastography (NIVE) in detecting early vascular changes in overweight and obese children

Evaluate non-invasive vascular elastography (NIVE) in detecting vascular changes associated with obese children. Case-control study to evaluate NIVE in 120 children, 60 with elevated body mass index (BMI) (≥ 85th percentile for age and sex). Participants were randomly selected from a longitudinal cohort, evaluating consequences of obesity in healthy children with one obese parent. Radiofrequency ultrasound videos of the common carotid artery were obtained. The carotid wall was segmented and NIVE applied to measure cumulated axial strain (CAS), cumulated axial translation (CAT), cumulated lateral translation (CLT), maximal shear strain (Max |SSE|), and intima-media thickness (IMT). Multivariate analyses were used controlling for age, sex, Tanner stage, blood pressure, and low-density lipoprotein. Statistical significance was set to 0.05-0.008. Participants were 10-13years old (mean 11.4 and 12.0, for normal and elevated BMI groups, p < 0.001), 58% and 63% boys, respectively. Groups differed in age, Tanner stage, and blood pressure. In the normal BMI group, there was weak correlation between systolic blood pressure and Max |SSE| (r = 0.316, p =0.01) and weak correlation between pulse pressure and Max |SSE| (r = 0.259, p =0.045). After Bonferroni correction, CAT was significantly higher in the elevated BMI group (0.68 ± 0.24mm vs. 0.52 ± 0.18mm), p < 0.001. CAS/CAT was significantly lower in the elevated BMI group (9.54 ± 4.8 vs. 13.34 ± 6.46), p = 0.001. IMT was significantly higher in the elevated BMI group (0.36 ± 0.05mm vs. 0.32 ± 0.05mm) before Bonferroni correction, p = 0.013. NIVE detected differences in CAT and CAS/CAT in elevated BMI children. NIVE is a promising technique to monitor radiological markers of subclinical atherosclerosis. • NIVE is a non-invasive technique based on measurement of subsegmental focal deformation of vascular wall to detect subclinical changes in arterial wall compliance. • Children with elevated BMI showed increased carotid artery wall movement during systole, as compared to normal BMI children (mean 0.68 ± 0.24mm vs. 0.52 ± 0.18mm; p < 0.001) and a lower ratio of vascular wall strain to wall movement during systole (mean 9.54 ± 4.8 vs. 13.34 ± 6.46; p = 0.001). • The detection of these subclinical changes helps physicians in the stratification of children at risk of atherosclerosis and guides in the implementation of preventive measures.

Reduced Numerical Approximation of Reduced Fluid-Structure Interaction Problems With Applications in Hemodynamics

This paper deals with fast simulations of the haemodynamics in large arteries by considering a reduced model of the associated fluid-structure interaction problem, which in turn allows an additional reduction in terms of the numerical discretisation. The resulting method is both accurate and computationally cheap. This goal is achieved by means of two levels of reduction: first, we describe the model equations with a reduced mathematical formulation which allows to write the fluid-structure interaction problem as a Navier-Stokes system with non-standard boundary conditions; second, we employ numerical reduction techniques to further and drastically lower the computational costs. The non standard boundary condition is of a generalized Robin type, with a boundary mass and boundary stiffness terms accounting for the arterial wall compliance. The numerical reduction is obtained coupling two well-known techniques: the proper orthogonal decomposition and the reduced basis method, in particular the greedy algorithm. We start by reducing the numerical dimension of the problem at hand with a proper orthogonal decomposition and we measure the system energy with specific norms; this allows to take into account the different orders of magnitude of the state variables, the velocity and the pressure. Then, we introduce a strategy based on a greedy procedure which aims at enriching the reduced discretization space with low offline computational costs. As application, we consider a realistic haemodynamics problem with a perturbation in the boundary conditions and we show the good performances of the reduction techniques presented in the paper. The results obtained with the numerical reduction algorithm are compared with the one obtained by a standard finite element method.The gains obtained in term of CPU time are of three orders of magnitude.

Evaluation of pulmonary artery wall properties in congenital heart disease patients using cardiac magnetic resonance

Congenital heart disease patients (CHD) with complex right heart disease are often left with residual lesions that result in right ventricular (RV)-pulmonary artery (PA) dysfunction post surgery. The appropriate timing of re-intervention to correct these lesions is difficult to determine due to lack of suitable quantifiable diagnostic techniques. The PA wall (material) properties characterize the mechanical behavior of the PAs and thus, contribute significantly to the RV-PA function. Therefore, the arterial wall properties of the main PA (MPA), left PA (LPA), and right PA (RPA) of three CHD subjects with normal RV-PA function and anatomy were quantified using retrospective pressure-diameter data as input to a constitutive (material) model. Intra-vessel (MPA vs branched PAs) and inter-subject variability was observed in the wall properties and consequently, the arterial wall compliance and stress-stretch characteristics. The LPA was least compliant in comparison to the MPA and RPA. Also, the circumferential and axial stress in the PAs increased with the subject's age. Therefore, monitoring the wall properties of the individual PAs may provide valuable longitudinal (time-dependent) information on disease progression of CHD patients.

Infrapopliteal calcification patterns in critical limb ischemia: diagnostic, pathologic and therapeutic implications in the search for the endovascular holy grail.

Critical limb ischemia (CLI) represents the terminal stage of peripheral arterial disease (PAD) and is characterized by multilevel and multivessel disease. Amongst patients with infrainguinal disease, approximately one third have predominantly isolated infrapopliteal disease and the remaining two thirds, a combination of femoropopliteal and infrapopliteal disease. Isolated infrapopliteal disease is mainly seen in the elderly, diabetic, or dialysis-dependent patients. These patients have higher risk of amputation and shorter amputation-free survival. Infrapopliteal disease presents with either complex high-grade calcified tandem lesions in multiple vessels or with long chronic total occlusion (CTO) segments with plaques characterized by higher calcium and lower fibro-fatty content than the inflow vessels, as arterial calcium deposition increases as we progress distally in the arterial tree. Vascular calcification occurs in both intima and media. Intimal calcification leads to development of calcified atheroma and occlusive lesions. Medial calcification leads to stiffening and decrease in arterial wall elasticity and compliance leading to atherosclerosis, reduced perfusion, and PAD, increasing cardiovascular mortality among patients with end-stage renal disease. This article attempts to review the implications of the diverse pathologic patterns of calcium distribution in infrapopliteal vessels of CLI patients, on the diagnostic modalities, technological developments, and the evolution of therapeutic approaches to improve outcomes among these patients. A critical analysis of the currently available data is provided, pointing to the surprising omission on the role of calcium on outcomes, and future directions are discussed. Is infrapopliteal calcium a roadblock or the avenue towards new paths? Necessity remains the mother of invention.

Evaluation of Hemodynamics in a Prestressed and Compliant Tapered Femoral Artery Using an Optimization-Based Inverse Algorithm.

The important factors that affect the arterial wall compliance are the tissue properties of the arterial wall, the in vivo pulsatile pressure, and the prestressed condition of the artery. It is necessary to obtain the load-free geometry for determining the physiological level of prestress in the arterial wall. The previously developed optimization-based inverse algorithm was improved to obtain the load-free geometry and the wall prestress of an idealized tapered femoral artery of a dog under varying arterial wall properties. The compliance of the artery was also evaluated over a range of systemic pressures (72.5-140.7 mmHg), associated blood flows, and artery wall properties using the prestressed arterial geometry. The results showed that the computed load-free outer diameter at the inlet of the tapered artery was 6.7%, 9.0%, and 12% smaller than the corresponding in vivo diameter for the 25% softer, baseline, and 25% stiffer arterial wall properties, respectively. In contrast, the variations in the prestressed geometry and circumferential wall prestress were less than 2% for variable arterial wall properties. The computed compliance at the inlet of the prestressed artery for the baseline arterial wall property was 0.34%, 0.19%, and 0.13% diameter change/mmHg for time-averaged pressures of 72.5, 104.1, and 140.7 mmHg, respectively. However, the variation in compliance due to the change in arterial wall property was less than 6%. The load-free and prestressed geometries of the idealized tapered femoral artery were accurately (error within 1.2% of the in vivo geometry) computed under variable arterial wall properties using the modified inverse algorithm. Based on the blood-arterial wall interaction results, the arterial wall compliance was influenced significantly by the change in average pressure. In contrast, the change in arterial wall property did not influence the arterial wall compliance.

New technologies and applications for drug-coated balloons

Drug-eluting stents (DES) represent nowadays the gold standard treatment for coronary artery disease. Despite the safety and efficacy, and favorable long-term clinical outcomes of new generation DES, their use is still associated with a not negligible risk of long-term events, related to the presence of a definitive prosthesis in the vessel wall. In addition, DES implantation is not always desirable in particular anatomic settings (small vessels, bifurcations) or in patients with higher bleeding risk. In recent years, drug-coated balloons (DCB) have been developed to overcome some of these limitations, offering a combined mechanical (balloon dilation) and biological therapy (drug-release). In the coronary setting, there is already a clear indication for the treatment of in-stent restenosis, but recent studies showed favorable results also when DCB are used for the treatment of de novo lesions.Regarding peripheral artery disease management, conventional transcatheter therapies with balloon angioplasty, atherectomy and stents are limited by high restenosis rates; in addition, stent implantation in lower limb vessels alter artery wall compliance, increasing stiffness, with a higher risk of restenosis and stent fracture. DCB represent a good alternative and have shown good safety and efficacy also in this setting.

Numerical Analysis of Arterial Plaque Thickness and its Impact on Artery Wall Compliance

A numerical analysis was completed on the influence of plaque on the compliance of an artery wall. The analysis allowed a systematic variation of the transluminal pressure difference and plaque thickness. Included in the analysis was a sheath of surrounding tissue that provides support during the cyclical deformation. The analysis incorporated progressively thicker layers of plaque to quantify their impact on the artery compliance. It was found that the presence of plaque plays a significant role in reducing the compliance. It is also shown that modest reductions in plaque thickness can result in large changes in the compliance and a positive health outcome. The calculations also included only a health artery (absence of plaque). The healthy artery possessed the largest compliance of the cases.

Abstract 19579: An Experimental Evaluation of the Compliance Mismatch Effects for Four Stent-graft Devices and a Multi-layer Flow Modulator (MFM) Device for the Treatment of Abdominal Aortic Aneurysms

Purpose: To experimentally investigate the arterial wall/device compliance mismatch of four stent-graft devices and a multi-layer flow modulator within the supra- and infra-renal locations for the treatment of Abdominal Aortic Aneurysms (AAA). Methods: Five devices were tested under physiologically flow conditions within a flow simulator system comprising of a patient-specific thin-walled flexible AAA model with replicated intraluminal thrombus (ILT) supported by the spinal column. Arterial pressure/diameter measurements were monitored and recorded at the supra- and infra-renal regions and various hemodynamic indicators were obtained to assess the effects of compliance mismatch. Results: At the suprarenal region, all devices except the Excluder™, significantly decreased the compliance by 10 - 21% (p&lt;0.002) and increased the stiffness values by 5 - 21% (p&lt;0.001). At the infrarenal region, three devices (Endurant™ and Excluder™) significantly decreased the compliance by 13 - 26% (p&lt;0.001), while the other three devices (MFM™, Zenith™ and Fortron™) did not significantly change the aortic compliance (p&gt;0.057). There was a variation of 10.9 - 16.0 m/s in pulse wave velocities with an increase of 8 - 238% (p&lt;0.001) in the reflection coefficient for all devices. The Excluder™ and Endurant TM devices doubled the infrarenal unstented median elastic modulus value (p&lt;0.001). Conclusions: Commercially available endovascular devices lower the arterial wall compliance and increase the wall stiffness at the stent/arterial wall interface by varying amounts. The Excluder™ was found to be the most compliant in the surprarenal region, while the MFM™ device was the most compliant in the infrarenal region.

In Vitro Model of Physiological and Pathological Blood Flow with Application to Investigations of Vascular Cell Remodeling.

Vascular disease is a common cause of death within the United States. Herein, we present a method to examine the contribution of flow dynamics towards vascular disease pathologies. Unhealthy arteries often present with wall stiffening, scarring, or partial stenosis which may all affect fluid flow rates, and the magnitude of pulsatile flow, or pulsatility index. Replication of various flow conditions is the result of tuning a flow pressure damping chamber downstream of a blood pump. Introduction of air within a closed flow system allows for a compressible medium to absorb pulsatile pressure from the pump, and therefore vary the pulsatility index. The method described herein is simply reproduced, with highly controllable input, and easily measurable results. Some limitations are recreation of the complex physiological pulse waveform, which is only approximated by the system. Endothelial cells, smooth muscle cells, and fibroblasts are affected by the blood flow through the artery. The dynamic component of blood flow is determined by the cardiac output and arterial wall compliance. Vascular cell mechano-transduction of flow dynamics may trigger cytokine release and cross-talk between cell types within the artery. Co-culture of vascular cells is a more accurate picture reflecting cell-cell interaction on the blood vessel wall and vascular response to mechanical signaling. Contribution of flow dynamics, including the cell response to the dynamic and mean (or steady) components of flow, is therefore an important metric in determining disease pathology and treatment efficacy. Through introducing an in vitro co-culture model and pressure damping downstream of blood pump which produces simulated cardiac output, various arterial disease pathologies may be investigated.

Peripheral vascular stiffness, assessed with two-dimensional speckle tracking versus the degree of coronary artery calcification, evaluated by tomographic coronary artery calcification index.

IntroductionEven in asymptomatic patients, the result of atherosclerosis progression is deterioration of the function and morphology of the artery wall. Two-dimensional speckle-tracking (2DST) is a sonographic technique that allows for precise evaluation of arterial wall compliance. Together with measurement of intima-media thickness (IMT), it can be applied for quick and non-invasive assessment of the progression of peripheral artery atherosclerosis.Material and methodsFifty-eight patients of mean age 61 years (SD 10.6) underwent cardiac computed tomography (CT) and subsequent ultrasonographic evaluation of the left common carotid artery. The calcium score was calculated according to the Agatston method and compared with IMT, circumferential strain variables assessed by 2DST, conventional arterial stiffness parameters (β-stiffness index and elastic modulus) and clinical data. Intra-observer and inter-observer agreement was evaluated.ResultsStrain variables and IMT differed significantly in patients with calcium score (CS) > 0 and CS = 0. Moreover, they correlated with CS, systolic blood pressure and age of patients. Conventional stiffness parameters were not able to identify the group of patients with calcifications present in the coronary arteries. For the 2DST technique, interclass and intraclass agreements were 84.83% and 94.42% respectively.ConclusionsCircumferential strain variables assessed by 2DST and measurement of IMT can be used for evaluation of peripheral artery deterioration in patients until the 6th decade of life. These parameters reflect the development of calcifications in coronary arteries and, more importantly, can be used for a more detailed estimation of the atherosclerosis risk in patients with CS = 0.

Fluid–structure interaction analysis of the left coronary artery with variable angulation

The aim of this study is to elucidate the correlation between coronary artery branch angulation, local mechanical and haemodynamic forces at the vicinity of bifurcation. Using a coupled fluid–structure interaction (FSI) modelling approach, five idealized left coronary artery models with various angles ranging from 70° to 110° were developed to investigate the influence of branch angulations. In addition, one CT image-based model was reconstructed to further demonstrate the medical application potential of the proposed FSI coupling method. The results show that the angulation strongly alters its mechanical stress distribution, and the instantaneous wall shear stress distributions are substantially moderated by the arterial wall compliance. As high tensile stress is hypothesized to cause stenosis, the left circumflex side bifurcation shoulder is indicated to induce atherosclerotic changes with a high tendency for wide-angled models.

The vascular endothelium in diabetes and its potential as a therapeutic target

The vascular endothelium in diabetes and its potential as a therapeutic target

Impedance-based outflow boundary conditions for human carotid haemodynamics

In this study, we develop structured tree outflow boundary conditions for modelling the human carotid haemodynamics. The model geometry was reconstructed through computerised tomography scan. Unsteady-state computational fluid dynamic analyses were performed under different conditions using a commercial software package ADINA R&D, Inc., (Watertown, MA, USA) in order to assess the impact of the boundary conditions on the flow variables. In particular, the results showed that the peripheral vessels massively impact the pressure while the flow is relatively unaffected. As an example of application of these outflow conditions, an unsteady fluid-structure interaction (FSI) simulation was carried out and the dependence of the wall shear stress (WSS) on the arterial wall compliance in the carotid bifurcation was studied. In particular, a comparison between FSI and rigid-wall models was conducted. Results showed that the WSS distributions were substantially affected by the diameter variation of the arterial wall. In particular, even similar WSS distributions were found for both cases, and differences in the computed WSS values were also found.