Key result
In an in vitro model, bileaflet mechanical aortic valve dysfunction increased the particle residence index and altered Lagrangian coherent structures, leading to elevated accumulated shear stresses that may promote thrombosis.
Why the study?
The study aimed to explore the Lagrangian nature of fluid transport downstream of a bileaflet mechanical aortic valve under different clinically relevant malfunction scenarios.
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In vitro modeling demonstrates that mechanical aortic valve dysfunction significantly alters fluid transport, increases particle residence time, and redistributes shear stresses in the ascending aorta.
This experimental study aims to explore the Lagrangian nature of fluid transport downstream of a bileaflet mechanical aortic valve under different malfunction scenarios that might be encountered clinically. Time-resolved planar particle image velocimetry measurements are performed to extract instantaneous velocity fields downstream of the bileaflet mechanical valve implanted in an elastic aortic model. The results show an increase in particle residence time with the severity of malfunction. This is attributed to the expansion of the recirculation regions downstream of the valve. The time-evolution of Lagrangian coherent structures over one cardiac cycle (using finite-time Lyapunov exponent fields) shows the effect of valve dysfunction on the material transport and its barriers inside the aorta. The unbalanced flow through the dysfunctional leaflets leads to a significant redistribution of the LCS, thus the fluid transport along the ascending aorta. Moreover, a new technique for the evaluation of the highest accumulated shear stresses is applied along the Lagrangian trajectory of particles being released from the extracted Lagrangian coherent structures where the highest stretching occurs. Finally, the induced non-laminar flow behavior by the valve dysfunction is analyzed using the time-frequency spectra of velocity signals at selected points in the ascending aorta.
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Darwish et al. (2020) studied Aortic valve dysfunction (in vitro model). Bileaflet mechanical aortic valve dysfunction vs. Normal valve operation was evaluated on Particle Residence Index (PRI) and accumulated shear stress. In an in vitro model, bileaflet mechanical aortic valve dysfunction increased the particle residence index and altered Lagrangian coherent structures, leading to elevated accumulated shear stresses that may promote thrombosis.
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