Turbulent Systolic Flow Downstream of a Bioprosthetic Aortic Valve: Velocity Spectra, Wall Shear Stresses, and Turbulent Dissipation Rates

Becsek, Barna Errol Mario; Pietrasanta, Leonardo; Obrist, Dominik

doi:10.3389/fphys.2020.577188

Cited by 35 publications

(47 citation statements)

References 41 publications

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“…This quantitative evidence highlights the presence of well-developed turbulent flow mostly confined in the (growing) shear layers and it corroborates the earlier observation that LI leads to significantly higher levels of turbulence. The spectra agree reasonably well with the spectra presented by Becsek et al ( 13 ) who studied a surgical bioprosthetic valve using a computational model. The quantitative agreement is best for the LI, whereas the UI shows lower energy levels than the data of Becsek et al…”

Section: Discussionsupporting

confidence: 88%

“…Moreover, fluttering of the leaflets was observed from the axial high speed recordings in both implantation configurations. This fluttering was similar to one found for surgical valves in experimental and numerical studies ( 13 , 41 ) and may further compromise the TAVs long-term performance ( 42 ).…”

Section: Discussionsupporting

confidence: 80%

“…Turbulence might be considered as one of the detrimental phenomena that could affect the long-term performance of TAV and lead over time to clinically adverse events. Turbulent flow is not only directly related to increased transvalvular pressure gradients ( 13 ) but also to structural valve deterioration (SVD) caused by excessive stress loads on the valve's leaflets ( 14 , 15 ). Turbulence could also lead to endothelial lesions and aorta remodeling due to unphysiological wall shear stress ( 16 ), as well as thrombus formation due to the activation of platelets ( 17 , 18 ).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 88%

Section: Discussionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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 used forward model comprises a high-order finitedifference flow solver for the Navier-Stokes equations for the Direct Numerical Simulation (DNS) of turbulent incompressible flow (31) which is thoroughly validated and has been used for several complex flow configurations (32)(33)(34) and recently for the study of fluid-structure interaction problems (35,36). The numerical forecast provided by the forward model are decomposed in an expectation value (ensemble-average) and its fluctuations.…”

Section: Introductionmentioning

confidence: 99%

Data Assimilation by Stochastic Ensemble Kalman Filtering to Enhance Turbulent Cardiovascular Flow Data From Under-Resolved Observations

Marinis

Obrist

2021

Front. Cardiovasc. Med.

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We propose a data assimilation methodology that can be used to enhance the spatial and temporal resolution of voxel-based data as it may be obtained from biomedical imaging modalities. It can be used to improve the assessment of turbulent blood flow in large vessels by combining observed data with a computational fluid dynamics solver. The methodology is based on a Stochastic Ensemble Kalman Filter (SEnKF) approach and geared toward pulsatile and turbulent flow configurations. We describe the observed flow fields by a mean value and its covariance. These flow fields are combined with forecasts obtained from a direct numerical simulation of the flow field. The method is validated against canonical pulsatile and turbulent flows. Finally, it is applied to a clinically relevant configuration, namely the flow downstream of a bioprosthetic valve in an aorta phantom. It is demonstrated how the 4D flow field obtained from experimental observations can be enhanced by the data assimilation algorithm. Results show that the presented method is promising for future use with in vivo data from 4D Flow Magnetic Resonance Imaging (4D Flow MRI). 4D Flow MRI returns spatially and temporally averaged flow fields that are limited by the spatial and the temporal resolution of the tool. These averaged flow fields and the associated uncertainty might be used as observation data in the context of the proposed methodology.

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“…In addition to the study reported by Lee and colleagues 1 in this issue, which analyzes the relationships among leaflet fluttering frequency, valve size, and leaflet tissue thickness, 2 independent studies that also used sophisticated computational models have provided concordant findings. 2,3 The results of all 3 studies emphasize that leaflet fluttering is more relevant to bioprosthetic valve performance and durability than commonly believed.…”

mentioning

confidence: 95%

Commentary: Leaflet fluttering of bioprosthetic valve—Does it matter?

Obrist¹,

Carrel²

2021

JTCVS Open

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Turbulent Systolic Flow Downstream of a Bioprosthetic Aortic Valve: Velocity Spectra, Wall Shear Stresses, and Turbulent Dissipation Rates

Cited by 35 publications

References 41 publications

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

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

Data Assimilation by Stochastic Ensemble Kalman Filtering to Enhance Turbulent Cardiovascular Flow Data From Under-Resolved Observations

Commentary: Leaflet fluttering of bioprosthetic valve—Does it matter?

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