| 1. |
- Jonnagiri, Raghuvir, et al.
(författare)
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Influence of aortic valve morphology on vortical structures and wall shear stress
- 2023
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Ingår i: Medical and Biological Engineering and Computing. - : Springer Nature. - 0140-0118 .- 1741-0444. ; 61:6, s. 1489-1506
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to assess the association between valve morphology and vortical structures quantitatively and to highlight the influence of valve morphology/orientation on aorta’s susceptibility to shear stress, both proximal and distal. Four-dimensional phase-contrast magnetic resonance imaging (4D PCMRI) data of 6 subjects, 3 with tricuspid aortic valve (TAV) and 3 with functionally bicuspid aortic values (BAV) with right-left coronary leaflet fusion, were processed and analyzed for vorticity and wall shear stress trends. Computational fluid dynamics (CFD) has been used with moving TAV and BAV valve designs in patient-specific aortae to compare with in vivo shear stress data. Vorticity from 4D PCMRI data about the aortic centerline demonstrated that TAVs had a higher number of vortical flow structures than BAVs at peak systole. Coalescing of flow structures was shown to be possible in the arch region of all subjects. Wall shear stress (WSS) distribution from CFD results at the aortic root is predominantly symmetric for TAVs but highly asymmetric for BAVs with the region opposite the raphe (fusion location of underdeveloped leaflets) being subjected to higher WSS. Asymmetry in the size and number of leaflets in BAVs and TAVs significantly influence vortical structures and WSS in the proximal aorta for all valve types and distal aorta for certain valve orientations of BAV. Graphical Abstract: Analysis of vortical structures using 4D PCMRI data (on the left side) and wall shear stress data using CFD (on the right side). [Figure not available: see fulltext.].
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| 2. |
- Sundström, Elias, et al.
(författare)
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Blood Speckle Imaging : An Emerging Method for Perioperative Evaluation of Subaortic and Aortic Valvar Repair
- 2023
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Ingår i: Bioengineering. - : MDPI AG. - 2306-5354. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Background: This article presents the use of blood speckle Imaging (BSI) as an echocardiographic approach for the pre- and post-operative evaluation of subaortic membrane resection and aortic valve repair. Method: BSI, employing block-matching algorithms, provided detailed visualization of flow patterns and quantification of parameters from ultrasound data. The 9-year-old patient underwent subaortic membrane resection and peeling extensions of the membrane from under the ventricular-facing surface of all three aortic valve leaflets. Result: Post-operatively, BSI demonstrated improvements in hemodynamic patterns, where quantified changes in flow velocities showed no signs of stenosis and trivial regurgitation. The asymmetric jet with a shear layer and flow reversal on the posterior aspect of the aorta was corrected resulting in reduced wall shear stress on the anterior aspect and reduced oscillatory shear index, which is considered a contributing element in cellular alterations in the structure of the aortic wall. Conclusion: This proof-of-concept study demonstrates the potential of BSI as an emerging echocardiographic approach for evaluating subaortic and aortic valvar repair. BSI enhances the quantitative evaluation of the left ventricular outflow tract of immediate surgical outcomes beyond traditional echocardiographic parameters and aids in post-operative decision-making. However, larger studies are needed to validate these findings and establish standardized protocols for clinical implementation.
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| 3. |
- Sundström, Elias, et al.
(författare)
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Impact of Variation in Commissural Angle between Fused Leaflets in the Functionally Bicuspid Aortic Valve on Hemodynamics and Tissue Biomechanics
- 2023
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Ingår i: Bioengineering. - : MDPI AG. - 2306-5354. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- In subjects with functionally bicuspid aortic valves (BAVs) with fusion between the coronary leaflets, there is a natural variation of the commissural angle. What is not fully understood is how this variation influences the hemodynamics and tissue biomechanics. These variables may influence valvar durability and function, both in the native valve and following repair, and influence ongoing aortic dilation. A 3D aortic valvar model was reconstructed from a patient with a normal trileaflet aortic valve using cardiac magnetic resonance (CMR) imaging. Fluid–structure interaction (FSI) simulations were used to compare the effects of the varying commissural angles between the non-coronary with its adjacent coronary leaflet. The results showed that the BAV with very asymmetric commissures ((Formula presented.) degree commissural angle) reduces the aortic opening area during peak systole and with a jet that impacts on the right posterior wall proximally of the ascending aorta, giving rise to elevated wall shear stress. This manifests in a shear layer with a retrograde flow and strong swirling towards the fused leaflet side. In contrast, a more symmetrical commissural angle ((Formula presented.) degree commissural angle) reduces the jet impact on the posterior wall and leads to a linear decrease in stress and strain levels in the non-fused non-coronary leaflet. These findings highlight the importance of considering the commissural angle in the progression of aortic valvar stenosis, the regional distribution of stresses and strain levels experienced by the leaflets which may predispose to valvar deterioration, and progression in thoracic aortic dilation in patients with functionally bicuspid aortic valves. Understanding the hemodynamics and biomechanics of the functionally bicuspid aortic valve and its variation in structure may provide insight into predicting the risk of aortic valve dysfunction and thoracic aortic dilation, which could inform clinical decision making and potentially lead to improved aortic valvar surgical outcomes.
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