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1
Friedman, Morton H., Heather A. Himburg, and Jeffrey A. LaMack. "Statistical Hemodynamics: A Tool for Evaluating the Effect of Fluid Dynamic Forces on Vascular Biology In Vivo." Journal of Biomechanical Engineering 128, no. 6 (May 16, 2006): 965–68. http://dx.doi.org/10.1115/1.2354212.
Анотація:
Background. In vivo experimentation is the most realistic approach for exploring the vascular biological response to the hemodynamic stresses that are present in life. Post-mortem vascular casting has been used to define the in vivo geometry for hemodynamic simulation; however, this procedure damages or destroys the tissue and cells on which biological assays are to be performed. Method of Approach. Two statistical approaches, regional (RSH) and linear (LSH) statistical hemodynamics, are proposed and illustrated, in which flow simulations from one series of experiments are used to define a best estimate of the hemodynamic environment in a second series. As an illustration of the technique, RSH is used to compare the gene expression profiles of regions of the proximal external iliac arteries of swine exposed to different levels of time-average shear stress. Results. The results indicate that higher shears promote a more atheroprotective expression phenotype in porcine arterial endothelium. Conclusion. Statistical hemodynamics provides a realistic estimate of the hemodynamic stress on vascular tissue that can be correlated against biological response.
2
Stahl, Janneck, Anna Bernovskis, Daniel Behme, Sylvia Saalfeld, and Philipp Berg. "Impact of patient-specific inflow boundary conditions on intracranial aneurysm hemodynamics." Current Directions in Biomedical Engineering 8, no. 1 (July 1, 2022): 125–28. http://dx.doi.org/10.1515/cdbme-2022-0032.
Анотація:
Abstract For hemodynamic simulations of intracranial aneurysms boundary conditions (BC) are required. In most cases, these are not patient-specific and thus do not reflect the real flow conditions in the patient. This study investigates the influence of patient-specific inflow BC on intra-aneurysmal hemodynamics. The focus lies on gender and age variations of the patients. To asses the impact, four different inflow curves representing the velocity profile of the inflow over one cardiac cycle is modeled. These four inflow BC are varied in the simulations of each aneurysm from selected subgroups. From the results of the simulations, the hemodynamic parameters are determined for each inflow BC and the percent differences between inflow BC are determined. The results show that the hemodynamic parameters are not robust to varying inflow BC. It can be seen that age has more influence on the hemodynamic parameters than gender. This study demonstrates the dependence of valid hemodynamic parameters on realistic inflow BC. Thus, if available, patient-specific inflow curves are recommended.
3
Grygoryan, R. D., and T. V. Aksenova. "Simulations of hypertrophied heart’s hemodynamics." PROBLEMS IN PROGRAMMING, no. 2-3 (June 2016): 254–63. http://dx.doi.org/10.15407/pp2016.02-03.254.
Анотація:
The paper describes the modeling technology and the main results of the simulation of hemodynamic effects of cardiac hypertrophy (HH), conducted using previously published mathematical model (MM) [9]. The dynamics of hemodynamic abnormalities are not modeled. MM simulates changes in the central hemodynamics at different degrees and forms of myocardial hypertrophy (MH). Software technology provides a simulation of three types of HH: a) adaptive HH arising in response to the chronic lack of the systemic circulation; b) abnormal HH, which is at the extreme stage of adaptive HH; c) abnormal MH of left ventricle. The first two versions of HH have been simulated by increasing of myocardium’s stiffness, while the third version of HH is simulated via additional decrease of the unstressed volume of the left ventricle. For each version of HH a compensatory potential of self-regulation mechanisms (model uncontrolled cardiovascular system) is studied, and then similar opportunities of baroreflex regulators of hemodynamics have been evaluated. HM satisfactorily reproduces the main changes in blood pressure, cardiac output, and heart rate. The likely role of cell energy mechanisms in the cardiovascular system adaptation to high loads is discussed. The simulator is an autonomous program which can be both a tool to support the medical-physiological research and an educational means for demonstrating causal relationships to medical students. An implementation of the program in a more general program-modeling complex focused on the identification of patterns of functioning of super-human energy is planned.
4
Popović, Zoran B., Umesh N. Khot, Gian M. Novaro, Fernando Casas, Neil L. Greenberg, Mario J. Garcia, Gary S. Francis, and James D. Thomas. "Effects of sodium nitroprusside in aortic stenosis associated with severe heart failure: pressure-volume loop analysis using a numerical model." American Journal of Physiology-Heart and Circulatory Physiology 288, no. 1 (January 2005): H416—H423. http://dx.doi.org/10.1152/ajpheart.00615.2004.
Анотація:
In the recently published clinical study [Use of Nitroprusside in Left Ventricular Dysfunction and Obstructive Aortic Valve Disease (UNLOAD)], sodium nitroprusside (SNP) improved cardiac function in patients with severe aortic stenosis (AS) and left ventricular (LV) systolic dysfunction. We explored the possible mechanisms of these findings using a series of numerical simulations. A closed-loop lumped parameters model that consists of 24 differential equations relating pressure and flow throughout the circulation was used to analyze the effects of varying hemodynamic conditions in AS. Hemodynamic data from UNLOAD study subjects were used to construct the initial simulation. Systemic vascular resistance (SVR), heart rate, and aortic valve area were directly entered into the model while end-systolic and end-diastolic pressure-volume (P-V) relationships were adjusted using previously published data to match modeled and observed end-systolic and end-diastolic pressures and volumes. Initial simulation of SNP treatment by a reduction of SVR was not adequate. To obtain realistic model hemodynamics that reliably reproduce SNP treatment effects, we performed a series of simulations while simultaneously changing end-systolic elastance ( Ees), end-systolic volume at zero pressure (V0), and diastolic P-V shift. Our data indicate that either an Ees increase or V0 decrease is necessary to obtain realistic model hemodynamics. In five patients, we corroborated our findings by using the model to duplicate individual P-V loops obtained before and during SNP treatment. In conclusion, using a numerical model, we identified ventricular function parameters that are responsible for improved hemodynamics during SNP infusion in AS with LV dysfunction.
5
Jeken-Rico, Pablo, Aurèle Goetz, Philippe Meliga, Aurélien Larcher, Yigit Özpeynirci, and Elie Hachem. "Evaluating the Impact of Domain Boundaries on Hemodynamics in Intracranial Aneurysms within the Circle of Willis." Fluids 9, no. 1 (December 21, 2023): 1. http://dx.doi.org/10.3390/fluids9010001.
Анотація:
Hemodynamic simulations are increasingly used to study vascular diseases such as Intracranial Aneurysms (IA) and to further develop treatment options. However, due to limited data, certain aspects must rely on heuristics, especially at the simulation’s distal ends. In the literature, Murray’s Law is often used to model the outflow split based on vessel cross-section area; however, this poses challenges for the communicating arteries in the Circle of Willis (CoW). In this study, we contribute by assessing the impact of Murray’s Law in patient-specific geometries featuring IA at the posterior communication. We simulate different domain extensions representing common modelling choices and establish Full CoW simulations as a baseline to evaluate the effect of these modelling assumptions on hemodynamic indicators, focusing on IA growth and rupture-related factors such as the Wall Shear Stress (WSS) and Oscillatory Shear Index (OSI). Our findings reveal qualitative alterations in hemodynamics when not modeling posterior communication. Comparisons between computing the anterior circulation and computing the whole Circle of Willis reveal that quantitative changes in WSS may reach up to 80%, highlighting the significance of modelling choices in assessing IA risks and treatment strategies.
6
Niemann, Annika, Samuel Voß, Riikka Tulamo, Simon Weigand, Bernhard Preim, Philipp Berg, and Sylvia Saalfeld. "Complex wall modeling for hemodynamic simulations of intracranial aneurysms based on histologic images." International Journal of Computer Assisted Radiology and Surgery 16, no. 4 (March 14, 2021): 597–607. http://dx.doi.org/10.1007/s11548-021-02334-z.
Анотація:
Abstract Purpose For the evaluation and rupture risk assessment of intracranial aneurysms, clinical, morphological and hemodynamic parameters are analyzed. The reliability of intracranial hemodynamic simulations strongly depends on the underlying models. Due to the missing information about the intracranial vessel wall, the patient-specific wall thickness is often neglected as well as the specific physiological and pathological properties of the vessel wall. Methods In this work, we present a model for structural simulations with patient-specific wall thickness including different tissue types based on postmortem histologic image data. Images of histologic 2D slices from intracranial aneurysms were manually segmented in nine tissue classes. After virtual inflation, they were combined into 3D models. This approach yields multiple 3D models of the inner and outer wall and different tissue parts as a prerequisite for subsequent simulations. Result We presented a pipeline to generate 3D models of aneurysms with respect to the different tissue textures occurring in the wall. First experiments show that including the variance of the tissue in the structural simulation affect the simulation result. Especially at the interfaces between neighboring tissue classes, the larger influence of stiffer components on the stability equilibrium became obvious. Conclusion The presented approach enables the creation of a geometric model with differentiated wall tissue. This information can be used for different applications, like hemodynamic simulations, to increase the modeling accuracy.
7
Grygoryan, R. D., A. G. Degoda, T. V. Lyudovyk, and O. I. Yurchak. "Simulations of human hemodynamic responses to blood temperature and volume changes." PROBLEMS IN PROGRAMMING, no. 1 (January 2023): 19–29. http://dx.doi.org/10.15407/pp2023.01.019.
Анотація:
An advanced version (AV) of special software based on modified quantitative models of mechanisms that provide the overall control of human circulation is proposed. AV essentially expands the range of tasks concerning the modeling of cardiovascular physiology, in particular, the range of mechanisms controlling cardiac function, vascular hemodynamics, and total blood volume under unstable internal/ external physiochemical environments. The models are verified on data representing hemodynamic responses to certain physical tests. In the publication, two test scenarios, namely blood temperature and volume dynamic alterations, have been simulated and analyzed in detail. The user-friendly interface provides all stages of preparation and analysis of computer simulation. The PC-based simulator can also be used for educational purposes.
8
Brambila-Solórzano, Alberto, Federico Méndez-Lavielle, Jorge Luis Naude, Gregorio Josué Martínez-Sánchez, Azael García-Rebolledo, Benjamín Hernández, and Carlos Escobar-del Pozo. "Influence of Blood Rheology and Turbulence Models in the Numerical Simulation of Aneurysms." Bioengineering 10, no. 10 (October 8, 2023): 1170. http://dx.doi.org/10.3390/bioengineering10101170.
Анотація:
An aneurysm is a vascular malformation that can be classified according to its location (cerebral, aortic) or shape (saccular, fusiform, and mycotic). Recently, the study of blood flow interaction with aneurysms has gained attention from physicians and engineers. Shear stresses, oscillatory shear index (OSI), gradient oscillatory number (GON), and residence time have been used as variables to describe the hemodynamics as well as the origin and evolution of aneurysms. However, the causes and hemodynamic conditions that promote their growth are still under debate. The present work presents numerical simulations of three types of aneurysms: two aortic and one cerebral. Simulation results showed that the blood rheology is not relevant for aortic aneurysms. However, for the cerebral aneurysm case, blood rheology could play a relevant role in the hemodynamics. The evaluated turbulence models showed equivalent results in both cases. Lastly, a simulation considering the fluid–structure interaction (FSI) showed that this phenomenon is the dominant factor for aneurysm simulation.
9
Korte, J., P. Groschopp, and P. Berg. "Resolution-based comparative analysis of 4D-phase-contrast magnetic resonance images and hemodynamic simulations of the aortic arch." Current Directions in Biomedical Engineering 9, no. 1 (September 1, 2023): 650–53. http://dx.doi.org/10.1515/cdbme-2023-1163.
Анотація:
Abstract Introduction: In this study, phase-contrast magnetic resonance imaging (PC-MRI) 4D flow data for patients with bicuspid aortic valve (BAV) were analyzed based on the spatial resolution of the images. BAV is a congenital heart defect characterized by the presence of two cusps in the aortic valve, leading to various complications. PC-MRI is a noninvasive imaging technique used to assess the hemodynamics in patients. However, interpretation of PC-MRI data can be challenging due to complex hemodynamics, which makes numerical simulations necessary to complement the results. Methods:Within this study PC-MRI 4D flow data in the aortic arch (AA) were compared with hemodynamic numerical simulations based on the MRI resolution for six patient-specific AAs with BAV. First, the segmentations were reconstructed and divided into three groups based on the resolution. Second, the numerical simulations were performed and resulting hemodynamics compared to PC-MRI results at three time points in the cardiac cycle using velocity and wall shear stress. Results: Results from group 1 (highest resolution) show an overestimation of wall shear stress (WSS) values during peaksystole in the three arteries and along the AA and descending aorta (DAo). Nevertheless, velocity mean values show an overall good agreement. Group 2 shows higher velocity magnitudes in the simulation than in PC-MRI. Within group 3, velocity values differ from the measurements. Conclusion: The study shows that with a low resolution, flow patterns can already be evaluated based on PC-MRI, but to get an insight into the flow quantitatively a higher resolution is necessary.
10
Chen, Yan, Masaharu Kobayashi, Changyoung Yuhn, and Marie Oshima. "Development of a 3D Vascular Network Visualization Platform for One-Dimensional Hemodynamic Simulation." Bioengineering 11, no. 4 (March 26, 2024): 313. http://dx.doi.org/10.3390/bioengineering11040313.
Анотація:
Recent advancements in computational performance and medical simulation technology have made significant strides, particularly in predictive diagnosis. This study focuses on the blood flow simulation reduced-order models, which provide swift and cost-effective solutions for complex vascular systems, positioning them as practical alternatives to 3D simulations in resource-limited medical settings. The paper introduces a visualization platform for patient-specific and image-based 1D–0D simulations. This platform covers the entire workflow, from modeling to dynamic 3D visualization of simulation results. Two case studies on, respectively, carotid stenosis and arterial remodeling demonstrate its utility in blood flow simulation applications.
11
Hoi, Yiemeng, Hui Meng, Scott H. Woodward, Bernard R. Bendok, Ricardo A. Hanel, Lee R. Guterman, and L. Nelson Hopkins. "Effects of arterial geometry on aneurysm growth: three-dimensional computational fluid dynamics study." Journal of Neurosurgery 101, no. 4 (October 2004): 676–81. http://dx.doi.org/10.3171/jns.2004.101.4.0676.
Анотація:
Object. Few researchers have quantified the role of arterial geometry in the pathogenesis of saccular cerebral aneurysms. The authors investigated the effects of parent artery geometry on aneurysm hemodynamics and assessed the implications relative to aneurysm growth and treatment effectiveness. Methods. The hemodynamics of three-dimensional saccular aneurysms arising from the lateral wall of arteries with varying arterial curves (starting with a straight vessel model) and neck sizes were studied using a computational fluid dynamics analysis. The effects of these geometric parameters on hemodynamic parameters, including flow velocity, aneurysm wall shear stress (WSS), and area of elevated WSS during the cardiac cycle (time-dependent impact zone), were quantified. Unlike simulations involving aneurysms located on straight arteries, blood flow inertia (centrifugal effects) rather than viscous diffusion was the predominant force driving blood into aneurysm sacs on curved arteries. As the degree of arterial curvature increased, flow impingement on the distal side of the neck intensified, leading to elevations in the WSS and enlargement of the impact zone at the distal side of the aneurysm neck. Conclusions. Based on these simulations the authors postulate that lateral saccular aneurysms located on more curved arteries are subjected to higher hemodynamic stresses. Saccular aneurysms with wider necks have larger impact zones. The large impact zone at the distal side of the aneurysm neck correlates well with other findings, implicating this zone as the most likely site of aneurysm growth or regrowth of treated lesions. To protect against high hemodynamic stresses, protection of the distal side of the aneurysm neck from flow impingement is critical.
12
Hyun, S., C. Kleinstreuer, P. W. Longest, and C. Chen. "Particle-Hemodynamics Simulations and Design Options for Surgical Reconstruction of Diseased Carotid Artery Bifurcations." Journal of Biomechanical Engineering 126, no. 2 (April 1, 2004): 188–95. http://dx.doi.org/10.1115/1.1688777.
Анотація:
Based on the hypothesis that aggravating hemodynamic factors play a key role in the onset of arterial diseases, the methodology of “virtual prototyping” of branching blood vessels was applied to diseased external carotid artery (ECA) segments. The goals were to understand the underlying particle-hemodynamics and to provide various geometric design options for improved surgical reconstruction based on the minimization of critical hemodynamic wall parameters (HWPs). First, a representative carotid artery bifurcation (CAB) and then CABs with stenosed ECAs, i.e., a distally occluded ECA and an ECA stump, were analyzed based on transient three-dimensional blood flow solutions, employing a user-enhanced commercial finite volume code. Specifically, the HWPs, i.e., oscillatory shear index, wall shear stress angle gradient, near-wall residence time of monocytes, and near-wall helicity angle difference were evaluated to compare the merits of each design option, including a reconstructed near-optimal junction which generates the lowest HWP-values. The results provide physical insight to the biofluid dynamics of branching blood vessels and guide vascular surgeons as well as stent manufacturers towards interventions leading to high sustained patency rates.
13
Wu, Yihao, Hui Xing, Qingyu Zhang, and Dongke Sun. "Numerical Study on Dynamics of Blood Cell Migration and Deformation in Atherosclerotic Vessels." Mathematics 10, no. 12 (June 11, 2022): 2022. http://dx.doi.org/10.3390/math10122022.
Анотація:
A phase field model is used to study the effect of atherosclerotic plaque on hemodynamics. The migration of cells in blood flows is described by a set of multiple phase field equations, which incorporate elastic energies and the interacting effects of cells. Several simulations are carried out to reveal the influences of initial velocities of blood cells, cellular elasticity and block rates of hemodynamic vessels. The results show that the cell deformation increases with the growth of the initial active velocity and block rate but with the decrease of the cellular elasticity. The atherosclerotic plaque not only affects the deformation and migration of cells but also can promote the variation in hemodynamic properties. The atherosclerotic plaque causes a burst in cell velocity, and the greater the block rate and cellular elasticity, the more dramatic the variation of instantaneous velocity. The present work demonstrates that the phase field method could be extended to reveal formation atherosclerosis at the microscopic level from the perspective of hemodynamics.
14
Quicken, Sjeng, Barend Mees, Niek Zonnebeld, Jan Tordoir, Wouter Huberts, and Tammo Delhaas. "A realistic arteriovenous dialysis graft model for hemodynamic simulations." PLOS ONE 17, no. 7 (July 21, 2022): e0269825. http://dx.doi.org/10.1371/journal.pone.0269825.
Анотація:
Objective The hemodynamic benefit of novel arteriovenous graft (AVG) designs is typically assessed using computational models that assume highly idealized graft configurations and/or simplified boundary conditions representing the peripheral vasculature. The objective of this study is to evaluate whether idealized AVG models are suitable for hemodynamic evaluation of new graft designs, or whether more realistic models are required. Methods An idealized and a realistic, clinical imaging based, parametrized AVG geometry were created. Furthermore, two physiological boundary condition models were developed to represent the peripheral vasculature. We assessed how graft geometry (idealized or realistic) and applied boundary condition models of the peripheral vasculature (physiological or distal zero-flow) impacted hemodynamic metrics related to AVG dysfunction. Results Anastomotic regions exposed to high WSS (>7, ≤40 Pa), very high WSS (>40 Pa) and highly oscillatory WSS were larger in the simulations using the realistic AVG geometry. The magnitude of velocity perturbations in the venous segment was up to 1.7 times larger in the realistic AVG geometry compared to the idealized one. When applying a (non-physiological zero-flow) boundary condition that neglected blood flow to and from the peripheral vasculature, we observed large regions exposed to highly oscillatory WSS. These regions could not be observed when using either of the newly developed distal boundary condition models. Conclusion Hemodynamic metrics related to AVG dysfunction are highly dependent on the geometry and the distal boundary condition model used. Consequently, the hemodynamic benefit of a novel graft design can be misrepresented when using idealized AVG modelling setups.
15
Kolachalama, Vijaya B., Neil W. Bressloff, and Prasanth B. Nair. "Mining data from hemodynamic simulations via Bayesian emulation." BioMedical Engineering OnLine 6, no. 1 (2007): 47. http://dx.doi.org/10.1186/1475-925x-6-47.
16
Spilker, Ryan L., and Charles A. Taylor. "Tuning Multidomain Hemodynamic Simulations to Match Physiological Measurements." Annals of Biomedical Engineering 38, no. 8 (March 30, 2010): 2635–48. http://dx.doi.org/10.1007/s10439-010-0011-9.
17
Gilmanov, Anvar, Alexander Barker, Henryk Stolarski, and Fotis Sotiropoulos. "Image-Guided Fluid-Structure Interaction Simulation of Transvalvular Hemodynamics: Quantifying the Effects of Varying Aortic Valve Leaflet Thickness." Fluids 4, no. 3 (June 29, 2019): 119. http://dx.doi.org/10.3390/fluids4030119.
Анотація:
When flow-induced forces are altered at the blood vessel, maladaptive remodeling can occur. One reason such remodeling may occur has to do with the abnormal functioning of the aortic heart valve due to disease, calcification, injury, or an improperly-designed prosthetic valve, which restricts the opening of the valve leaflets and drastically alters the hemodynamics in the ascending aorta. While the specifics underlying the fundamental mechanisms leading to changes in heart valve function may differ from one cause to another, one common and important change is in leaflet stiffness and/or mass. Here, we examine the link between valve stiffness and mass and the hemodynamic environment in aorta by coupling magnetic resonance imaging (MRI) with high-resolution fluid–structure interaction (FSI) computational fluid dynamics to simulate blood flow in a patient-specific model. The thoracic aorta and a native aortic valve were re-constructed in the FSI model from the MRI data and used for the simulations. The effect of valve stiffness and mass is parametrically investigated by varying the thickness (h) of the leaflets (h = 0.6, 2, 4 mm). The FSI simulations were designed to investigate systematically progressively higher levels of valve stiffness by increasing valve thickness and quantifying hemodynamic parameters known to be linked to aortopathy and valve disease. The computed results reveal dramatic differences in all hemodynamic parameters: (1) the geometric orifice area (GOA), (2) the maximum velocity V max of the jet passing through the aortic orifice area, (3) the rate of energy dissipation E ˙ diss ( t ) , (4) the total loss of energy E diss , (5) the kinetic energy of the blood flow E kin ( t ) , and (6) the average magnitude of vorticity Ω a ( t ) , illustrating the change in hemodynamics that occur due to the presence of aortic valve stenosis.
18
Korte, Jana, Thomas Rauwolf, Jan-Niklas Thiel, Andreas Mitrasch, Paulina Groschopp, Michael Neidlin, Alexander Schmeißer, Rüdiger Braun-Dullaeus, and Philipp Berg. "Hemodynamic Assessment of the Pathological Left Ventricle Function under Rest and Exercise Conditions." Fluids 8, no. 2 (February 16, 2023): 71. http://dx.doi.org/10.3390/fluids8020071.
Анотація:
Purpose: The analysis of pathological human left ventricular hemodynamics using high-resolved image-based blood flow simulations shows a major potential for examining mitral valve insufficiency (MI) under exercise conditions. Since capturing and simulating the patient-specific movement of the left ventricle (LV) during rest and exercise is challenging, this study aims to propose a workflow to analyze the hemodynamics within the pathologically moving LV. Methods: Patient-specific ultrasound (US) data of ten patients with MI in different stages were captured with three-dimensional real-time echocardiography. US measurements were performed while patients were resting and while doing handgrip exercise (2–4 min work). Patient-specific hemodynamic simulations were carried out based on the captured ventricular wall movement. Velocity and kinetic energy were analyzed for rest and exercise and for the different MI stages. Results: The results reveal a dependency of the kinetic energy over time in the ventricular volume curves. Concerning the comparison between rest and exercise, the left ventricular function reveals lower systolic kinetic energy under exercise (kinetic energy normalized by EDV; mean ± standard deviation: rest = 0.16 ± 0.14; exercise = 0.06 ± 0.05; p-value = 0.04). Comparing patients with non-limiting (MI I) and mild/moderate (MI II/III) MI, lower velocities (mean ± standard deviation: non-limiting = 0.10 ± 0.03; mild/moderate = 0.06 ± 0.02; p-value = 0.01) and lower diastolic kinetic energy (kinetic energy normalized by EDV; mean ± standard deviation: non-limiting = 0.45 ± 0.30; mild/moderate = 0.20 ± 0.19; p-value = 0.03) were found for the latter. Conclusion: With the proposed workflow, the hemodynamics within LVs with MI can be analyzed under rest and exercise. The results reveal the importance of the patient-specific wall movement when analyzing intraventricular hemodynamics. These findings can be further used within patient-specific simulations, based on varying the imaging and segmentation methods.
19
Berg, Philipp, Sylvia Saalfeld, Samuel Voß, Oliver Beuing, and Gábor Janiga. "A review on the reliability of hemodynamic modeling in intracranial aneurysms: why computational fluid dynamics alone cannot solve the equation." Neurosurgical Focus 47, no. 1 (July 2019): E15. http://dx.doi.org/10.3171/2019.4.focus19181.
Анотація:
Computational blood flow modeling in intracranial aneurysms (IAs) has enormous potential for the assessment of highly resolved hemodynamics and derived wall stresses. This results in an improved knowledge in important research fields, such as rupture risk assessment and treatment optimization. However, due to the requirement of assumptions and simplifications, its applicability in a clinical context remains limited.This review article focuses on the main aspects along the interdisciplinary modeling chain and highlights the circumstance that computational fluid dynamics (CFD) simulations are embedded in a multiprocess workflow. These aspects include imaging-related steps, the setup of realistic hemodynamic simulations, and the analysis of multidimensional computational results. To condense the broad knowledge, specific recommendations are provided at the end of each subsection.Overall, various individual substudies exist in the literature that have evaluated relevant technical aspects. In this regard, the importance of precise vessel segmentations for the simulation outcome is emphasized. Furthermore, the accuracy of the computational model strongly depends on the specific research question. Additionally, standardization in the context of flow analysis is required to enable an objective comparison of research findings and to avoid confusion within the medical community. Finally, uncertainty quantification and validation studies should always accompany numerical investigations.In conclusion, this review aims for an improved awareness among physicians regarding potential sources of error in hemodynamic modeling for IAs. Although CFD is a powerful methodology, it cannot provide reliable information, if pre- and postsimulation steps are inaccurately carried out. From this, future studies can be critically evaluated and real benefits can be differentiated from results that have been acquired based on technically inaccurate procedures.
20
Xiang, Jianping, Jihnhee Yu, Kenneth V. Snyder, Elad I. Levy, Adnan H. Siddiqui, and Hui Meng. "Hemodynamic–morphological discriminant models for intracranial aneurysm rupture remain stable with increasing sample size." Journal of NeuroInterventional Surgery 8, no. 1 (December 8, 2014): 104–10. http://dx.doi.org/10.1136/neurintsurg-2014-011477.
Анотація:
BackgroundWe previously established three logistic regression models for discriminating intracranial aneurysm rupture status based on morphological and hemodynamic analysis of 119 aneurysms. In this study, we tested if these models would remain stable with increasing sample size, and investigated sample sizes required for various confidence levels (CIs).MethodsWe augmented our previous dataset of 119 aneurysms into a new dataset of 204 samples by collecting an additional 85 consecutive aneurysms, on which we performed flow simulation and calculated morphological and hemodynamic parameters, as done previously. We performed univariate significance tests on these parameters, and multivariate logistic regression on significant parameters. The new regression models were compared against the original models. Receiver operating characteristics analysis was applied to compare the performance of regression models. Furthermore, we performed regression analysis based on bootstrapping resampling statistical simulations to explore how many aneurysm cases were required to generate stable models.ResultsUnivariate tests of the 204 aneurysms generated an identical list of significant morphological and hemodynamic parameters as previously (from the analysis of 119 cases). Furthermore, multivariate regression analysis produced three parsimonious predictive models that were almost identical to the previous ones, with model coefficients that had narrower CIs than the original ones. Bootstrapping showed that 10%, 5%, 2%, and 1% convergence levels of CI required 120, 200, 500, and 900 aneurysms, respectively.ConclusionsOur original hemodynamic–morphological rupture prediction models are stable and improve with increasing sample size. Results from resampling statistical simulations provide guidance for designing future large multi-population studies.
21
JANELA, J., A. SEQUEIRA, G. PONTRELLI, S. SUCCI, and S. UBERTINI. "UNSTRUCTURED LATTICE BOLTZMANN METHOD FOR HEMODYNAMIC FLOWS WITH SHEAR-DEPENDENT VISCOSITY." International Journal of Modern Physics C 21, no. 06 (June 2010): 795–811. http://dx.doi.org/10.1142/s0129183110015488.
Анотація:
The lattice Boltzmann formulation on unstructured grids (ULBE) is compared against semi-analytical solutions of non-Newtonian flows in straight channels, as well as with finite-element simulations in stenosed geometries. In all cases, satisfactory agreement is found, lending further credit to the ULBE method as a potentially useful method for the numerical simulation of small-scale hemodynamic flows, such as blood flow in capillaries and arterioles.
22
Veeturi, Sricharan S., Tatsat R. Patel, Ammad A. Baig, Aichi Chien, Andre Monteiro, Muhammad Waqas, Kenneth V. Snyder, Adnan H. Siddiqui, and Vincent M. Tutino. "Hemodynamic Analysis Shows High Wall Shear Stress Is Associated with Intraoperatively Observed Thin Wall Regions of Intracranial Aneurysms." Journal of Cardiovascular Development and Disease 9, no. 12 (November 29, 2022): 424. http://dx.doi.org/10.3390/jcdd9120424.
Анотація:
Background: Studying the relationship between hemodynamics and local intracranial aneurysm (IA) pathobiology can help us understand the natural history of IA. We characterized the relationship between the IA wall appearance, using intraoperative imaging, and the hemodynamics from CFD simulations. Methods: Three-dimensional geometries of 15 IAs were constructed and used for CFD. Two-dimensional intraoperative images were subjected to wall classification using a machine learning approach, after which the wall type was mapped onto the 3D surface. IA wall regions included thick (white), normal (purple-crimson), and thin/translucent (red) regions. IA-wide and local statistical analyses were performed to assess the relationship between hemodynamics and wall type. Results: Thin regions of the IA sac had significantly higher WSS, Normalized WSS, WSS Divergence and Transverse WSS, compared to both normal and thick regions. Thicker regions tended to co-locate with significantly higher RRT than thin regions. These trends were observed on a local scale as well. Regression analysis showed a significant positive correlation between WSS and thin regions and a significant negative correlation between WSSD and thick regions. Conclusion: Hemodynamic simulation results were associated with the intraoperatively observed IA wall type. We consistently found that elevated WSS and WSSNorm were associated with thin regions of the IA wall rather than thick and normal regions.
23
Tang, Elaine, Zhenglun (Alan) Wei, Mark A. Fogel, Alessandro Veneziani, and Ajit P. Yoganathan. "Fluid-Structure Interaction Simulation of an Intra-Atrial Fontan Connection." Biology 9, no. 12 (November 24, 2020): 412. http://dx.doi.org/10.3390/biology9120412.
Анотація:
Total cavopulmonary connection (TCPC) hemodynamics has been hypothesized to be associated with long-term complications in single ventricle heart defect patients. Rigid wall assumption has been commonly used when evaluating TCPC hemodynamics using computational fluid dynamics (CFD) simulation. Previous study has evaluated impact of wall compliance on extra-cardiac TCPC hemodynamics using fluid-structure interaction (FSI) simulation. However, the impact of ignoring wall compliance on the presumably more compliant intra-atrial TCPC hemodynamics is not fully understood. To narrow this knowledge gap, this study aims to investigate impact of wall compliance on an intra-atrial TCPC hemodynamics. A patient-specific model of an intra-atrial TCPC is simulated with an FSI model. Patient-specific 3D TCPC anatomies were reconstructed from transverse cardiovascular magnetic resonance images. Patient-specific vessel flow rate from phase-contrast magnetic resonance imaging (MRI) at the Fontan pathway and the superior vena cava under resting condition were prescribed at the inlets. From the FSI simulation, the degree of wall deformation was compared with in vivo wall deformation from phase-contrast MRI data as validation of the FSI model. Then, TCPC flow structure, power loss and hepatic flow distribution (HFD) were compared between rigid wall and FSI simulation. There were differences in instantaneous pressure drop, power loss and HFD between rigid wall and FSI simulations, but no difference in the time-averaged quantities. The findings of this study support the use of a rigid wall assumption on evaluation of time-averaged intra-atrial TCPC hemodynamic metric under resting breath-held condition.
24
Hoque, K. E., S. Sawall, M. A. Hoque, and M. S. Hossain. "Hemodynamic Simulations to Identify Irregularities in Coronary Artery Models." Journal of Advances in Mathematics and Computer Science 28, no. 5 (September 11, 2018): 1–19. http://dx.doi.org/10.9734/jamcs/2018/43598.
25
Fonte, T. A., I. E. Vignon-Clementel, C. A. Figueroa, J. A. Feinstein, and C. A. Taylor. "Three-dimensional simulations of hemodynamic factors in pulmonary hypertension." Journal of Biomechanics 39 (January 2006): S290—S291. http://dx.doi.org/10.1016/s0021-9290(06)84125-4.
26
Mansilla Alvarez, L. A., P. J. Blanco, C. A. Bulant, and R. A. Feijóo. "Towards fast hemodynamic simulations in large-scale circulatory networks." Computer Methods in Applied Mechanics and Engineering 344 (February 2019): 734–65. http://dx.doi.org/10.1016/j.cma.2018.10.032.
27
Lobachik, V. I., S. V. Abrosimov, V. V. Zhidkov, and D. K. Endeka. "Hemodynamic effects of microgravity and their ground-based simulations." Acta Astronautica 23 (1991): 35–40. http://dx.doi.org/10.1016/0094-5765(91)90097-o.
28
Torii, Ryo, Marie Oshima, Toshio Kobayashi, Kiyoshi Takagi, and Tayfun E. Tezduyar. "Influence of wall elasticity in patient-specific hemodynamic simulations." Computers & Fluids 36, no. 1 (January 2007): 160–68. http://dx.doi.org/10.1016/j.compfluid.2005.07.014.
29
Padhee, Swati, Mark Johnson, Hang Yi, Tanvi Banerjee, and Zifeng Yang. "Machine Learning for Aiding Blood Flow Velocity Estimation Based on Angiography." Bioengineering 9, no. 11 (October 28, 2022): 622. http://dx.doi.org/10.3390/bioengineering9110622.
Анотація:
Computational fluid dynamics (CFD) is widely employed to predict hemodynamic characteristics in arterial models, while not friendly to clinical applications due to the complexity of numerical simulations. Alternatively, this work proposed a framework to estimate hemodynamics in vessels based on angiography images using machine learning (ML) algorithms. First, the iodine contrast perfusion in blood was mimicked by a flow of dye diffusing into water in the experimentally validated CFD modeling. The generated projective images from simulations imitated the counterpart of light passing through the flow field as an analogy of X-ray imaging. Thus, the CFD simulation provides both the ground truth velocity field and projective images of dye flow patterns. The rough velocity field was estimated using the optical flow method (OFM) based on 53 projective images. ML training with least absolute shrinkage, selection operator and convolutional neural network was conducted with CFD velocity data as the ground truth and OFM velocity estimation as the input. The performance of each model was evaluated based on mean absolute error and mean squared error, where all models achieved or surpassed the criteria of 3 × 10−3 and 5 × 10−7 m/s, respectively, with a standard deviation less than 1 × 10−6 m/s. Finally, the interpretable regression and ML models were validated with over 613 image sets. The validation results showed that the employed ML model significantly reduced the error rate from 53.5% to 2.5% on average for the v-velocity estimation in comparison with CFD. The ML framework provided an alternative pathway to support clinical diagnosis by predicting hemodynamic information with high efficiency and accuracy.
30
Wu, Wei, Anastasios Nikolaos Panagopoulos, Charu Hasini Vasa, Mohammadali Sharzehee, Shijia Zhao, Saurabhi Samant, Usama M. Oguz, et al. "Patient-specific computational simulation of coronary artery bypass grafting." PLOS ONE 18, no. 3 (March 3, 2023): e0281423. http://dx.doi.org/10.1371/journal.pone.0281423.
Анотація:
Introduction Coronary artery bypass graft surgery (CABG) is an intervention in patients with extensive obstructive coronary artery disease diagnosed with invasive coronary angiography. Here we present and test a novel application of non-invasive computational assessment of coronary hemodynamics before and after bypass grafting. Methods and results We tested the computational CABG platform in n = 2 post-CABG patients. The computationally calculated fractional flow reserve showed high agreement with the angiography-based fractional flow reserve. Furthermore, we performed multiscale computational fluid dynamics simulations of pre- and post-CABG under simulated resting and hyperemic conditions in n = 2 patient-specific anatomies 3D reconstructed from coronary computed tomography angiography. We computationally created different degrees of stenosis in the left anterior descending artery, and we showed that increasing severity of native artery stenosis resulted in augmented flow through the graft and improvement of resting and hyperemic flow in the distal part of the grafted native artery. Conclusions We presented a comprehensive patient-specific computational platform that can simulate the hemodynamic conditions before and after CABG and faithfully reproduce the hemodynamic effects of bypass grafting on the native coronary artery flow. Further clinical studies are warranted to validate this preliminary data.
31
Nixon, Alexander M., Murat Gunel, and Bauer E. Sumpio. "The critical role of hemodynamics in the development of cerebral vascular disease." Journal of Neurosurgery 112, no. 6 (June 2010): 1240–53. http://dx.doi.org/10.3171/2009.10.jns09759.
Анотація:
Atherosclerosis and intracranial saccular aneurysms predictably localize in areas with complex arterial geometries such as bifurcations and curvatures. These sites are characterized by unique hemodynamic conditions that possibly influence the risk for these disorders. One hemodynamic parameter in particular has emerged as a key regulator of vascular biology—wall shear stress (WSS). Variations in geometry can change the distribution and magnitude of WSS, thus influencing the risk for vascular disorders. Computer simulations conducted using patient-specific data have suggested that departures from normal levels of WSS lead to aneurysm formation and progression. In addition, multiple studies indicate that disturbed flow and low WSS predispose patients to extracranial atherosclerosis, and particularly to carotid artery disease. Conversely, in the case of intracranial atherosclerosis, more studies are needed to provide a firm link between hemodynamics and atherogenesis. The recognition of WSS as an important factor in cerebral vascular disease may help to identify individuals at risk and guide treatment options.
32
Wan Ab Naim, Wan Naimah, Poo Balan Ganesan, Zhonghua Sun, Kok Han Chee, Shahrul Amry Hashim, and Einly Lim. "A Perspective Review on Numerical Simulations of Hemodynamics in Aortic Dissection." Scientific World Journal 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/652520.
Анотація:
Aortic dissection, characterized by separation of the layers of the aortic wall, poses a significant challenge for clinicians. While type A aortic dissection patients are normally managed using surgical treatment, optimal treatment strategy for type B aortic dissection remains controversial and requires further evaluation. Although aortic diameter measured by CT angiography has been clinically used as a guideline to predict dilation in aortic dissection, hemodynamic parameters (e.g., pressure and wall shear stress), geometrical factors, and composition of the aorta wall are known to substantially affect disease progression. Due to the limitations of cardiac imaging modalities, numerical simulations have been widely used for the prediction of disease progression and therapeutic outcomes, by providing detailed insights into the hemodynamics. This paper presents a comprehensive review of the existing numerical models developed to investigate reasons behind tear initiation and progression, as well as the effectiveness of various treatment strategies, particularly the stent graft treatment.
33
BENFOULA, A., L. HAMZA CHERIF, and K. N. HAKKOUM. "EVALUATION OF LEFT VENTRICULAR FILLING PRESSURE USING NUMERICAL MODELING." Journal of Mechanics in Medicine and Biology 20, no. 07 (September 2020): 2050043. http://dx.doi.org/10.1142/s0219519420500438.
Анотація:
The main objective of this work is to study the effect of blood pressure and viscosity on flow in a pathological and healthy anatomy. The method chosen for this project is the numerical simulation of fluid dynamics. First, a radiological database from Tlemcen hospital was studied in order to select a patient whose aortic anatomy is representative of the pathology studied in this research project. The left ventricle was segmented using SolidWork software. The exported data made it possible to model this geometry on Comsol software. The geometry has been idealized to make it comparable to a given healthy left ventricle geometry and present the main parameters which influence the ventricular hemodynamics. A first series of numerical simulations made it possible to highlight the hemodynamic disturbances associated with the pathology of interest and described extensively in the literature. A second series of numerical simulations made it possible to model the effect of blood viscosity on flow. All the results obtained, the modeling of the left ventricle, must be valid experimentally. This study therefore does not completely justify the treatment of ventricular dilation with a flow modulator but constitutes an important first step towards a proof of concept.
34
Sun, Y., M. Beshara, R. J. Lucariello, and S. A. Chiaramida. "A comprehensive model for right-left heart interaction under the influence of pericardium and baroreflex." American Journal of Physiology-Heart and Circulatory Physiology 272, no. 3 (March 1, 1997): H1499—H1515. http://dx.doi.org/10.1152/ajpheart.1997.272.3.h1499.
Анотація:
A phenomenological model of the cardiopulmonary circulation is developed with a focus on the interaction between the right heart and the left heart. The model predicts the hemodynamic consequences of changing circulatory parameters in terms of a broad spectrum of pressure and flow waveforms. Hemodynamics are characterized by use of an electrical analog incorporating mechanisms for transseptal pressure coupling, pericardial volume coupling, intrathoracic pressure, and baroreflex control of heart rate. Computer simulations are accomplished by numerically integrating 28 differential equations that contain nonlinear and time-varying coefficients. Validity of the model is supported by its accurate fit to clinical pressure and Doppler echocardiographic recordings. The model characterizes the hemodynamic waveforms for mitral stenosis, mitral regurgitation, left heart failure, right heart failure, cardiac tamponade, pulsus paradoxus, and the Valsalva maneuver. The wave shapes of pulmonary capillary wedge pressure under the above conditions are also accurately represented. Sensitivity analysis reveals that simulated hemodynamics are insensitive to most individual model parameters with the exception of afterload resistance, preload capacitances, intrathoracic pressure, contractility, and pericardial fluid volume. Baseline hemodynamics are minimally affected by transseptal coupling (up to 2%) and significantly affected by pericardial coupling (up to 20%). The model should be useful for quantitative studies of cardiopulmonary dynamics related to the right-left heart interaction under normal and disease conditions.
35
YANG, Jin You, and Yang Hong. "Numerical Simulations of the Non-Newtonian Blood Blow in Human Abdominal Artery Based on Reverse Engineering." Applied Mechanics and Materials 140 (November 2011): 195–99. http://dx.doi.org/10.4028/www.scientific.net/amm.140.195.
Анотація:
The method that combined the reverse engineering based on CT medical images and computational fluid dynamics (CFD) was used to perform simulation the Non-Newtonian blood fluid flow in human abdominal artery, then analyzed the hemodynamic condition about the bifurcation of human abdominal artery. A Non-Newtonian blood model (the Generalised Power Law) was used to study the hemodynamic parameters during entire cardiac cycle. Calculated results for the Non-Newtonian blood flow show us the methods performed in this study is suitable for numerical simulating the blood flow in human artery and investigating the relation between hemodynamic factors and vascular disease.
36
Sharzehee, Mohammadali, Yuan Chang, Jiang-ping Song, and Hai-Chao Han. "Hemodynamic effects of myocardial bridging in patients with hypertrophic cardiomyopathy." American Journal of Physiology-Heart and Circulatory Physiology 317, no. 6 (December 1, 2019): H1282—H1291. http://dx.doi.org/10.1152/ajpheart.00466.2019.
Анотація:
Myocardial bridging (MB) is linked to angina and myocardial ischemia and may lead to sudden cardiac death in patients with hypertrophic cardiomyopathy (HCM). However, it remains unclear how MB affect the coronary blood flow in HCM patients. The aim of this study was to assess the effects of MB on coronary hemodynamics in HCM patients. Fifteen patients with MB (7 HCM and 8 non-HCM controls) in their left anterior descending (LAD) coronary artery were chosen. Transient computational fluid dynamics (CFD) simulations were conducted in anatomically realistic models of diseased (with MB) and virtually healthy (without MB) LAD from these patients, reconstructed from biplane angiograms. Our CFD simulation results demonstrated that dynamic compression of MB led to diastolic flow disturbances and could significantly reduce the coronary flow in HCM patients as compared with non-HCM group ( P < 0.01). The pressure drop coefficient was remarkably higher ( P < 0.05) in HCM patients. The flow rate change is strongly correlated with both upstream Reynolds number and MB compression ratio, while the MB length has less impact on coronary flow. The hemodynamic results and clinical outcomes revealed that HCM patients with an MB compression ratio higher than 65% required a surgical intervention. In conclusion, the transient MB compression can significantly alter the diastolic flow pattern and wall shear stress distribution in HCM patients. HCM patients with severe MB may need a surgical intervention. NEW & NOTEWORTHY In this study, the hemodynamic significance of myocardial bridging (MB) in patients with hypertrophic cardiomyopathy (HCM) was investigated to provide valuable information for surgical decision-making. Our results illustrated that the transient MB compression led to complex flow patterns, which can significantly alter the diastolic flow and wall shear stress distribution. The hemodynamic results and clinical outcomes demonstrated that patients with HCM and an MB compression ratio higher than 65% required a surgical intervention.
37
Barahona, José, Alvaro Valencia, and María Torres. "Study of the Hemodynamics Effects of an Isolated Systolic Hypertension (ISH) Condition on Cerebral Aneurysms Models, Using FSI Simulations." Applied Sciences 11, no. 6 (March 15, 2021): 2595. http://dx.doi.org/10.3390/app11062595.
Анотація:
Hemodynamics is recognized as a relevant factor in the development and rupture of cerebral aneurysms, so further studies related to different physiological conditions in human represent an advance in understanding the pathology and rupture risk. In this paper, Fluid-structure interaction simulations (FSI) were carried out in six models of cerebral aneurysms, in order to study the hemodynamics effects of an isolated systolic hypertension (ISH) condition and compare it to a normal or normotensive pressure condition and a higher hypertension condition. Interestingly, the ISH condition showed, in general, the greatest hemodynamics changes, evidenced in the Time-Averaged Wall Shear Stress (TAWSS), Oscillatory Shear Index (OSI), and Relative Residence Time (RRT) parameters, with respect to a normal condition. These results could imply that a not high-pressure condition (ISH), characterized with a different shape and an abrupt change in its diastolic and systolic range may present more adverse hemodynamic changes compared to a higher-pressure condition (such as a hypertensive condition) and therefore have a greater incidence on the arterial wall remodeling and rupture risk.
38
Talaminos, Alejandro, Laura M. Roa, Antonio Álvarez, and Javier Reina. "Computational Hemodynamic Modeling of the Cardiovascular System." International Journal of System Dynamics Applications 3, no. 2 (April 2014): 81–98. http://dx.doi.org/10.4018/ijsda.2014040106.
Анотація:
Computational methods and modeling are widely used in many fields to study the dynamic behaviour of different phenomena. Currently, the use of these models is an accepted practice in the biomedical field. One of the most significant efforts in this direction is applied to the simulation and prediction of pathophysiological conditions that can affect different systems of the human body. In this work, the design and development of a computational model of the human cardiovascular system is proposed. The structure of the model has been built from a physiological base, considering some of the mechanisms associated to the cardiovascular system. Thus, the aim of the model is the prediction, heartbeat by heartbeat, of some hemodynamic variables from the cardiovascular system, in different pathophysiological cardiac situations. A modular approach to development of the model has been considered in order to include new knowledge that could force the model's hemodynamic. The model has been validated comparing the results obtained with hemodynamic values published by other authors. The results show the usefulness and applicability of the model developed. Thus, different simulations of some cardiac pathologies and physical exercise situations are presented, together with the dynamic behaviors of the different variables considered in the model.
39
Korte, Jana, Laurel Marsh, Franziska Gaidzik, Mariya Pravdivtseva, Naomi Larsen, and Philipp Berg. "Correlation of Black Blood MRI with Image- Based Blood Flow Simulations in Intracranial Aneurysms." Current Directions in Biomedical Engineering 7, no. 2 (October 1, 2021): 895–98. http://dx.doi.org/10.1515/cdbme-2021-2228.
Анотація:
Abstract Intracranial aneurysms (IA) is not-uncommon pathology of cerebral vessels. Vessel wall magnetic resonance imaging can visualize the vascular walls of IAs. In some aneurysms, the wall-adjacent and a luminal hyperintense signal was detected. The signal was attributed to the inflammation and specific hemodynamic features of aneurysms. But, up to now, the studies investigating luminal enhancement combined with flow analysis are limited. Therefore, in this study, investigation of the luminal enhancement is further carried out by comparison to computational fluid dynamics. The latter provides the possibility of calculating hemodynamic parameters, which can give information such as velocity, pressure, and shear stress fields throughout a heart cycle. The data of the IAs is specific to each patient and builds the basis for the enhancement analysis and simulations. Specific hemodynamic parameters like kinetic energy and vortex formation evaluated in the simulations show a dependency to signal suppression recorded with vessel wall magnetic resonance imaging
40
Arzani, Amirhossein, Ga-Young Suh, Ronald L. Dalman, and Shawn C. Shadden. "A longitudinal comparison of hemodynamics and intraluminal thrombus deposition in abdominal aortic aneurysms." American Journal of Physiology-Heart and Circulatory Physiology 307, no. 12 (December 15, 2014): H1786—H1795. http://dx.doi.org/10.1152/ajpheart.00461.2014.
Анотація:
Abdominal aortic aneurysm (AAA) is often accompanied by in traluminal thrombus (ILT), which complicates AAA progression and risk of rupture. Patient-specific computational fluid dynamics modeling of 10 small human AAA was performed to investigate relations between hemodynamics and ILT progression. The patients were imaged using magnetic resonance twice in a 2- to 3-yr interval. Wall content data were obtained by a planar T1-weighted fast spin echo black-blood scan, which enabled quantification of thrombus thickness at midaneurysm location during baseline and followup. Computational simulations with patient-specific geometry and boundary conditions were performed to quantify the hemodynamic parameters of time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and mean exposure time at baseline. Spatially resolved quantifications of the change in ILT thickness were compared with the different hemodynamic parameters. Regions of low OSI had the strongest correlation with ILT growth and demonstrated a statistically significant correlation coefficient. Prominent regions of high OSI (>0.4) and low TAWSS (<1 dyn/cm2) did not appear to coincide with locations of thrombus deposition.
41
Lei, M., C. Kleinstreuer, and J. P. Archie. "Hemodynamic Simulations and Computer-Aided Designs of Graft-Artery Junctions." Journal of Biomechanical Engineering 119, no. 3 (August 1, 1997): 343–48. http://dx.doi.org/10.1115/1.2796099.
Анотація:
Severe occlusion of graft–artery junctions due to restenosis, e.g., excessive tissue overgrowth and renewed plaque formation, may occur within a few months or years after bypass surgery. Our hypothesis is that nonuniform hemodynamics, represented by large sustained wall shear stress gradients, trigger abnormal biological processes leading to rapid restenosis and hence early graft failure. In turn, this problem may be significantly mitigated by designing graft-artery bypass configurations for which the wall shear stress gradient (WSSG) is approximately zero and hence nearly uniform hemodynamics are achieved. Focusing on the distal end of several femoral artery bypass junctions, a validated finite volume code has been used to compute the transient three-dimensional velocity vector fields and its first and second surface derivatives in order to test the idea. Specifically, it is shown that the Taylor patch, which generates higher patency rates than standard end-to-side anastomoses, exhibits lower WSSG levels than standard configurations, and that further geometric design improvements reduce the WSSG in magnitude and local extent even more.
42
Delestre, Olivier, and Pierre-Yves Lagrée. "A well-balanced finite volume scheme for 1D hemodynamic simulations." ESAIM: Proceedings 35 (March 2012): 222–27. http://dx.doi.org/10.1051/proc/201235018.
43
Sankaran, Sethuraman, Leo Grady, and Charles A. Taylor. "Impact of geometric uncertainty on hemodynamic simulations using machine learning." Computer Methods in Applied Mechanics and Engineering 297 (December 2015): 167–90. http://dx.doi.org/10.1016/j.cma.2015.08.014.
44
Zhu, Guang-Yu, Yuan Wei, Ya-Li Su, Qi Yuan, and Cheng-Fu Yang. "Impacts of Internal Carotid Artery Revascularization on Flow in Anterior Communicating Artery Aneurysm: A Preliminary Multiscale Numerical Investigation." Applied Sciences 9, no. 19 (October 3, 2019): 4143. http://dx.doi.org/10.3390/app9194143.
Анотація:
The optimal management strategy of patients with concomitant anterior communicating artery aneurysm (ACoAA) and internal carotid artery (ICA) stenosis is unclear. This study aims to evaluate the impacts of unilateral ICA revascularization on hemodynamics factors associated with rupture in an ACoAA. In the present study, a multiscale computational model of ACoAA was developed by coupling zero-dimensional (0D) models of the cerebral vascular system with a three-dimensional (3D) patient-specific ACoAA model. Distributions of flow patterns, wall shear stress (WSS), relative residence time (RRT) and oscillating shear index (OSI) in the ACoAA under left ICA revascularization procedure were quantitatively assessed by using transient computational fluid dynamics (CFD) simulations. Our results showed that the revascularization procedures significantly changed the hemodynamic environments in the ACoAA. The flow disturbance in the ACoAA was enhanced by the resumed flow from the affected side. In addition, higher OSI (0.057 vs. 0.02), prolonged RRT (1.14 vs. 0.39) and larger low WSS area (66 vs. 50 mm2) in ACoAA were found in the non-stenotic case. These acute changes in hemodynamics after revascularization may elevate the rupture risk of ACoAA. The preliminary results validated the feasibility of predicting aneurismal hemodynamics characteristics in revascularization procedures by using multiscale CFD simulations, which would benefit the management of this group of patients.
45
Belaghit, Abdelhakem, B. Aour, M. Larabi, A. A. Tadjeddine, and S. Mebarki. "Numerical study of hemodynamics after stent implantation during the cardiac cycle." Journal of Mechanical Engineering and Sciences 15, no. 2 (June 10, 2021): 8016–28. http://dx.doi.org/10.15282/jmes.15.2.2021.07.0632.
Анотація:
The descending aortic aneurysm is one of the most catastrophic cardiovascular emergencies resulting in high mortality worldwide. Clinical observations have pointed out that stent implantation in the sick aorta should probably allow stabilization of the hemodynamic state of the patient's aorta. To better understand the hemodynamic impact of a stent-treated aneurysm, numerical simulations are used to evaluate hemodynamic parameters. These latter including flow profile, velocity distribution, aortic wall pressure and shear stress, which are difficult to measure in vivo. It should be noted that the numerical modeling assists in medical planning by providing patterns of blood circulation, in particular, the distribution of pressures and shear stresses in the wall. In this context, the pulsatile blood flow in the aneurysmal aorta with stent is studied by CFD (Computational Fluid Dynamics) simulations. Realistic boundary conditions time dependent are prescribed at the level of the different arteries of the complete aorta models. The hemodynamic profile of the aneurysmal aorta with stent was analyzed by contour planes of velocity vectors, pressures and shear stresses at different times during the cardiac cycle. The obtained results made it possible to show the effect of the stent on the improvement of the blood flow by solving the problems of hemodynamic disturbances in the aorta. The methodology used in this work has revealed detailed and necessary information for the cases studied and shows the interest of the numerical tool for diagnosis and surgery.
46
Ciocanel, Maria-Veronica, Tracy Stepien, Ioannis Sgouralis, and Anita Layton. "A Multicellular Vascular Model of the Renal Myogenic Response." Processes 6, no. 7 (July 17, 2018): 89. http://dx.doi.org/10.3390/pr6070089.
Анотація:
The myogenic response is a key autoregulatory mechanism in the mammalian kidney. Triggered by blood pressure perturbations, it is well established that the myogenic response is initiated in the renal afferent arteriole and mediated by alterations in muscle tone and vascular diameter that counterbalance hemodynamic perturbations. The entire process involves several subcellular, cellular, and vascular mechanisms whose interactions remain poorly understood. Here, we model and investigate the myogenic response of a multicellular segment of an afferent arteriole. Extending existing work, we focus on providing an accurate—but still computationally tractable—representation of the coupling among the involved levels. For individual muscle cells, we include detailed Ca2+ signaling, transmembrane transport of ions, kinetics of myosin light chain phosphorylation, and contraction mechanics. Intercellular interactions are mediated by gap junctions between muscle or endothelial cells. Additional interactions are mediated by hemodynamics. Simulations of time-independent pressure changes reveal regular vasoresponses throughout the model segment and stabilization of a physiological range of blood pressures (80–180 mmHg) in agreement with other modeling and experimental studies that assess steady autoregulation. Simulations of time-dependent perturbations reveal irregular vasoresponses and complex dynamics that may contribute to the complexity of dynamic autoregulation observed in vivo. The ability of the developed model to represent the myogenic response in a multiscale and realistic fashion, under feasible computational load, suggests that it can be incorporated as a key component into larger models of integrated renal hemodynamic regulation.
47
Herman, I. M., A. M. Brant, V. S. Warty, J. Bonaccorso, E. C. Klein, R. L. Kormos, and H. S. Borovetz. "Hemodynamics and the vascular endothelial cytoskeleton." Journal of Cell Biology 105, no. 1 (July 1, 1987): 291–302. http://dx.doi.org/10.1083/jcb.105.1.291.
Анотація:
Although there is considerable evidence to suggest that hemodynamics play an important role in vascular disease processes, the exact mechanisms are unknown. With this in mind, we have designed a pulsatile perfusion apparatus which reproducibly delivers pulsatile hemodynamics upon freshly excised canine carotid arteries in vitro. Quantifiable simulations included normotension with normal or lowered flow rates (120/80 mmHg, 120 and 40 ml/min), normotension with lowered or elevated transmural pressures (40-170 mmHg), and elevated pulse pressure (120 and 80 mmHg) with normal (150 ml/min) or elevated rates of flow (300 and 270 ml/min). Arterial biomechanical stresses and cellular behaviors were characterized biochemically and morphologically under all these stimulations which continued for 2-24 h. We found that increased pulse pressure alone had little effect on the total amount of radiolabeled [4-14C]cholesterol present within the medial compartment. However, normotension when coupled with altered transmural pressure yielded a three- to fourfold increase. Combinations of increased pulse pressure and flow potentiated cholesterol uptake by a factor of 10 when compared with normotension control values. Simulations that enhanced carotid arterial cholesterol uptake also influenced the endothelial cytoskeletal array of actin. Stress fibers were not present within the carotid endothelial cells of either the sham controls or the normotension and increased pulse pressure (normal flow) simulations. Endothelial cells lining carotids exposed to elevations in flow or those present within vessels perfused as per simulation b above assembled stress fibers (x = 4 and 10 per cell, respectively) within the time course of these studies. When endothelial cells were subjected to hemodynamic conditions that potentiated maximally cholesterol transport, no diffuse or stress fiber staining could be seen, but the cortical array of actin was intact. These results suggest that those biomechanical stresses that alter endothelial permeability and intimal integrity may do so via cytoskeletal actin signaling.
48
Stark, Anselm W., Andreas A. Giannopoulos, Alexander Pugachev, Isaac Shiri, Andreas Haeberlin, Lorenz Räber, Dominik Obrist, and Christoph Gräni. "Application of Patient-Specific Computational Fluid Dynamics in Anomalous Aortic Origin of Coronary Artery: A Systematic Review." Journal of Cardiovascular Development and Disease 10, no. 9 (September 6, 2023): 384. http://dx.doi.org/10.3390/jcdd10090384.
Анотація:
Anomalous aortic origin of a coronary artery (AAOCA) is a rare congenital heart condition with fixed and dynamic stenotic elements, potentially causing ischemia. Invasive coronary angiography under stress is the established method for assessing hemodynamics in AAOCA, yet it is costly, technically intricate, and uncomfortable. Computational fluid dynamics (CFD) simulations offer a noninvasive alternative for patient-specific hemodynamic analysis in AAOCA. This systematic review examines the role of CFD simulations in AAOCA, encompassing patient-specific modeling, noninvasive imaging-based boundary conditions, and flow characteristics. Screening articles using AAOCA and CFD-related terms prior to February 2023 yielded 19 publications, covering 370 patients. Over the past four years, 12 (63%) publications (259 patients) employed dedicated CFD models, whereas 7 (37%) publications (111 patients) used general-purpose CFD models. Dedicated CFD models were validated for fixed stenosis but lacked dynamic component representation. General-purpose CFD models exhibited variability and limitations, with fluid–solid interaction models showing promise. Interest in CFD modeling of AAOCA has surged recently, mainly utilizing dedicated models. However, these models inadequately replicate hemodynamics, necessitating novel CFD approaches to accurately simulate pathophysiological changes in AAOCA under stress conditions.
49
Chen, Aolin, Adi Azriff Basri, Norzian Bin Ismail, and Kamarul Arifin Ahmad. "The Numerical Analysis of Non-Newtonian Blood Flow in a Mechanical Heart Valve." Processes 11, no. 1 (December 24, 2022): 37. http://dx.doi.org/10.3390/pr11010037.
Анотація:
Background: The non-physiological structure of mechanical heart valves (MHVs) affects the blood flow field, especially the complex microstructure at the hinge. Numerous studies suggest that the blood flow field in the aortic area with an MHV can be considered Newtonian. However, the Newtonian assumption is occasionally unreasonable, where blood viscosity changes with shear rate, exhibiting non-Newtonian shear-thinning characteristics. Methods: In this research, a comprehensive study of the non-Newtonian effects on the hemodynamic behavior of MHVs was performed. The impact of the Newtonian hypothesis was investigated on the internal hemodynamics of MHVs. Several non-Newtonian and Newtonian models were used to analyze the chamber flow and blood viscosity. MHVs were modeled and placed in simplified arteries. After the unstructured mesh was generated, a simulation was performed in OpenFOAM to analyze its hemodynamic parameters. Results: In the study of the non-Newtonian viscosity model, the Casson model differs significantly from the Newtonian model, resulting in a 70.34% higher wall shear stress. In the modified Cross and Carreau models, the non-Newtonian behavior can significantly simulate blood in the MHV at different stages during initial and intermediate deceleration. The narrowing of the hinge region in particular, has a significant impact on evaluating blood rheology. The low flow rate and high wall shear force at the hinge can cause blood cell accumulation and injury time, resulting in hemolytic thrombosis. Conclusion: The results exhibit that the Newtonian hypothesis underestimates the hemodynamics of MHVs, whose complex structure leads to increased recirculation, stagnation, and eddy current structure, and a reasonable choice of blood viscosity model may improve the result accuracy. Modfied Cross and Carreau viscosity models effectively exhibit the shear-thinning behavior in MHV blood simulations.
50
Melzer, Helena-Sophie, Ralf Ahrens, Andreas E. Guber та Jakob Dohse. "The influence of strut-connectors in coronary stents: A comparison of numerical simulations and μPIV measurements". Current Directions in Biomedical Engineering 6, № 3 (1 вересня 2020): 392–95. http://dx.doi.org/10.1515/cdbme-2020-3101.
Анотація:
AbstractThis paper discusses the influence of different designs of strut-connectors of stents by numerical flow simulations and flow examinations using micro particle image velocimetry (μPIV). Many studies have shown that there is a correlation between the hemodynamics after stent implantation and the cause of biological responses like thrombosis and the in-stent restenosis. Recirculation areas may occur through a stent, which are considered to be the cause of these clinical complications. In this study, three different coronary stent designs are investigated and the hemodynamic effects from the different designs is presented. The study focuses on the design of the strut-connectors that connect two struts. Numerical simulations were performed to evaluate various flow features like recirculation zones, velocity profiles and wall shear stress (WSS) patterns. To verify the numerical results μPIVmeasurements were performed. It could be shown that the alignment in the main stream of the connectors influences the size and number of recirculation zones.