Analysis of Turbulence Effects in a Patient-Specific Aorta with Aortic Valve Stenosis

Manchester, Emily Louise; Pirola, Selene; Salmasi, Mohammad Yousuf; O’Regan, Declan P; Athanasiou, Thanos; Xu, Xiao Yun

doi:10.1007/s13239-021-00536-9

Cited by 39 publications

(34 citation statements)

References 51 publications

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“…For this reason, PC-MRI data are used to obtain reliable patient-specific flow inlet conditions in numerical computations rather than direct WSS estimations. However, it is necessary to stress out that uncertainties originating from functional MRI data acquisition and processing can also propagate at the simulated output ( 19 ). In literature, the effect of the uncertainties of inlet conditions from PC-MRI processing and of their propagation was analyzed in the particular context of the aorta.…”

Section: Introductionmentioning

confidence: 99%

On the Role and Effects of Uncertainties in Cardiovascular in silico Analyses

Celi

Vignali

Capellini

et al. 2021

Front. Med. Technol.

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The assessment of cardiovascular hemodynamics with computational techniques is establishing its fundamental contribution within the world of modern clinics. Great research interest was focused on the aortic vessel. The study of aortic flow, pressure, and stresses is at the basis of the understanding of complex pathologies such as aneurysms. Nevertheless, the computational approaches are still affected by sources of errors and uncertainties. These phenomena occur at different levels of the computational analysis, and they also strongly depend on the type of approach adopted. With the current study, the effect of error sources was characterized for an aortic case. In particular, the geometry of a patient-specific aorta structure was segmented at different phases of a cardiac cycle to be adopted in a computational analysis. Different levels of surface smoothing were imposed to define their influence on the numerical results. After this, three different simulation methods were imposed on the same geometry: a rigid wall computational fluid dynamics (CFD), a moving-wall CFD based on radial basis functions (RBF) CFD, and a fluid-structure interaction (FSI) simulation. The differences of the implemented methods were defined in terms of wall shear stress (WSS) analysis. In particular, for all the cases reported, the systolic WSS and the time-averaged WSS (TAWSS) were defined.

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Section: Introductionmentioning

confidence: 99%

On the Role and Effects of Uncertainties in Cardiovascular in silico Analyses

Celi

Vignali

Capellini

et al. 2021

Front. Med. Technol.

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“…Finally, we compare our results with a recent computational investigation by Manchester et al (45) who conducted large eddy simulations (LES) in a patient specific dilated ascending aorta with aortic valve stenosis and investigated the effect of turbulence in relation with energy losses and wall shear stresses. In their study, they recognize the high velocity jet entering the dilated ascending aorta as one of the primary sources of turbulence production.…”

Section: Turbulent Kinetic Energymentioning

confidence: 68%

Characterization of Turbulent Flow Behind a Transcatheter Aortic Valve in Different Implantation Positions

Pietrasanta

Zheng

Marinis

et al. 2022

Front. Cardiovasc. Med.

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The development of turbulence after transcatheter aortic valve (TAV) implantation may have detrimental effects on the long-term performance and durability of the valves. The characterization of turbulent flow generated after TAV implantation can provide fundamental insights to enhance implantation techniques. A self-expandable TAV was tested in a pulse replicator and the three-dimensional flow field was extracted by means of tomographic particle image velocimetry. The valve was fixed inside a silicone phantom mimicking the aortic root and the flow field was studied for two different supra-annular axial positions at peak systole. Fluctuating velocities and turbulent kinetic energy were compared between the two implantations. Velocity spectra were derived at different spatial positions in the turbulent wakes to characterize the turbulent flow. The valve presented similar overall flow topology but approximately 8% higher turbulent intensity in the lower implantation. In this configuration, axial views of the valve revealed smaller opening area and more corrugated leaflets during systole, as well as more accentuated pinwheeling during diastole. The difference arose from a lower degree of expansion of the TAV's stent inside the aortic lumen. These results suggest that the degree of expansion of the TAV in-situ is related to the onset of turbulence and that a smaller and less regular opening area might introduce flow instabilities that could be detrimental for the long-term performance of the valve. The present study highlights how implantation mismatches may affect the structure and intensity of the turbulent flow in the aortic root.

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“…The arterial wall is assumed rigid with a no-slip boundary condition. Full details on data acquisition and image processing can be found in our previous study ( Manchester et al, 2021 ).…”

Section: Methodsmentioning

confidence: 99%

“…There are numerous CFD studies into aortic haemodynamics, however the majority of these studies made the assumption of laminar flow. In recent years, there have been studies of aortic flows which do not assume laminarity and have shown disturbances to be present in aortas with and without pathologic conditions ( Lantz et al, 2012 ; Lantz et al, 2013 ; Miyazaki et al, 2017 ; Xu et al, 2018 ; Xu et al, 2020 ; Manchester et al, 2021 ). A recent study considered flow in the healthy aorta, deducing that physiological blood flow is non-laminar and displays blood flow disturbances ( Saqr et al, 2020 ).…”

Section: Introductionmentioning

confidence: 99%

“…The objective of this research is to evaluate the performance of different computational approaches used in simulations of patient-specific aortic flow. A patient with aortic valve stenosis was selected for this study as it showed blood flow disturbances ( Manchester et al, 2021 ) and is thus expected to provide a challenging case for the various computational approaches. Three simulations are conducted including low-resolution laminar, high-resolution laminar and large-eddy simulation, and detailed comparisons are made in terms of both laminar and turbulence parameters.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Computational Methodologies for Accurate Prediction of Wall Shear Stress and Turbulence Parameters in a Patient-Specific Aorta

Manchester

Pirola

Salmasi

et al. 2022

Front. Bioeng. Biotechnol.

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Background: Recent studies suggest that blood flow in main arteries is intrinsically disturbed, even under healthy conditions. Despite this, many computational fluid dynamics (CFD) analyses of aortic haemodynamics make the assumption of laminar flow, and best practices surrounding appropriate modelling choices are lacking. This study aims to address this gap by evaluating different modelling and post-processing approaches in simulations of a patient-specific aorta.Methods: Magnetic resonance imaging (MRI) and 4D flow MRI from a patient with aortic valve stenosis were used to reconstruct the aortic geometry and derive patient-specific inlet and outlet boundary conditions. Three different computational approaches were considered based on assumed laminar or assumed disturbed flow states including low-resolution laminar (LR-Laminar), high-resolution laminar (HR-Laminar) and large-eddy simulation (LES). Each simulation was ran for 30 cardiac cycles and post-processing was conducted on either the final cardiac cycle, or using a phase-averaged approach which utilised all 30 simulated cycles. Model capabilities were evaluated in terms of mean and turbulence-based parameters.Results: All simulation types, regardless of post-processing approach could correctly predict velocity values and flow patterns throughout the aorta. Lower resolution simulations could not accurately predict gradient-derived parameters including wall shear stress and viscous energy loss (largest differences up to 44.6% and 130.3%, respectively), although phase-averaging these parameters improved predictions. The HR-Laminar simulation produced more comparable results to LES with largest differences in wall shear stress and viscous energy loss parameters up to 5.1% and 11.6%, respectively. Laminar-based parameters were better estimated than turbulence-based parameters.Conclusion: Our findings suggest that well-resolved laminar simulations can accurately predict many laminar-based parameters in disturbed flows, but there is no clear benefit to running a HR-Laminar simulation over an LES simulation based on their comparable computational cost. Additionally, post-processing “typical” laminar simulation results with a phase-averaged approach is a simple and cost-effective way to improve accuracy of lower-resolution simulation results.

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Analysis of Turbulence Effects in a Patient-Specific Aorta with Aortic Valve Stenosis

Cited by 39 publications

References 51 publications

On the Role and Effects of Uncertainties in Cardiovascular in silico Analyses

On the Role and Effects of Uncertainties in Cardiovascular in silico Analyses

Characterization of Turbulent Flow Behind a Transcatheter Aortic Valve in Different Implantation Positions

Evaluation of Computational Methodologies for Accurate Prediction of Wall Shear Stress and Turbulence Parameters in a Patient-Specific Aorta

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