Journal Article10.1007/S10439-007-9411-X
Characterization of Hemodynamic Forces Induced by Mechanical Heart Valves: Reynolds vs. Viscous Stresses
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TL;DR: The overall levels of the viscous stresses are apparently too low to induce damage to red blood cells, but could potentially damage platelets, and it is shown that the so-called Reynolds shear stresses neither directly contribute to the mechanical load on blood cells nor is a proper measurement of the mechanical Load experienced by blood cells.
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Abstract: Bileaflet mechanical heart valves (BMHV) are widely used to replace diseased heart valves. Implantation of BMHV, however, has been linked with major complications, which are generally considered to be caused by mechanically induced damage of blood cells resulting from the non-physiological hemodynamics environment induced by BMHV, including regions of recirculating flow and elevated Reynolds (turbulence) shear stress levels. In this article, we analyze the results of 2D high-resolution velocity measurements and full 3D numerical simulation for pulsatile flow through a BMHV mounted in a model axisymmetric aorta to investigate the mechanical environment experienced by blood elements under physiologic conditions. We show that the so-called Reynolds shear stresses neither directly contribute to the mechanical load on blood cells nor is a proper measurement of the mechanical load experienced by blood cells. We also show that the overall levels of the viscous stresses, which comprise the actual flow environment experienced by cells, are apparently too low to induce damage to red blood cells, but could potentially damage platelets. The maximum instantaneous viscous shear stress observed throughout a cardiac cycle is <15 N/m2. Our analysis is restricted to the flow downstream of the valve leaflets and thus does not address other areas within the BMHV where potentially hemodynamically hazardous levels of viscous stresses could still occur (such as in the hinge gaps and leakage jets).
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Citations
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190
Fluid–structure interaction, immersed boundary-finite element method simulations of bio-prosthetic heart valves
TL;DR: The capabilities of the FSI solver are demonstrated by simulating the first fully three-dimensional fluid–structure interaction of tissue valves implanted in the aortic position during systole under physiologic flow conditions, and it is observed that the flow’s threefold symmetry breaks during the early systoles, questioning the three fold symmetry assumption of previous simulations.
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Direct numerical simulation of the pulsatile flow through an aortic bileaflet mechanical heart valve
TL;DR: In this paper, the authors focused on the direct numerical simulation of the pulsatile flow through a bileaflet mechanical heart valve under physiological conditions and in a realistic aortic root geometry, and the motion of the valve leaflets was computed from the forces exerted by the fluid on the structure both being considered as a single dynamical system.
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References
•Journal Article
Velocity measurements and flow patterns within the hinge region of a Medtronic Parallel bileaflet mechanical valve with clear housing.
TL;DR: The results suggest that the hinge design can significantly affect the washout capacity and thrombogenic potential of the Medtronic Parallel bileaflet mechanical heart valve.
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Orientation of tilting disc and bileaflet aortic valve substitutes for optimal hemodynamics
TL;DR: Hemodynamic performance of this valve type, regarding turbulence and pressure gradients, is close to normal physiology and superior to the bileaflet valve design.
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Models of flow-induced loading on blood cells in laminar and turbulent flow, with application to cardiovascular device flow.
Nathan J. Quinlan,Patrick Dooley +1 more
TL;DR: The model suggests that Reynolds stress alone is not an adequate predictor of cell damage in turbulent flow, and highlights the importance of the energy spectral density.
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Steady flow dynamics of prosthetic aortic heart valves: a comparative evaluation with PIV techniques
TL;DR: Flow visualization techniques, combined with velocity vector fields and Reynolds stresses mappings in the aortic root obtained from PIV, and pressure measurements were used to give an overall picture of the flow field of the prosthetic heart valves under steady flow conditions.
64
Turbulent stresses downstream of three mechanical aortic valve prostheses in human beings
Nygaard H,Nygaard H,Peter K. Paulsen,Peter K. Paulsen,J. Michael Hasenkam,J. Michael Hasenkam,Erik Morre Pedersen,Erik Morre Pedersen,Poul E. Rovsing,Poul E. Rovsing +9 more
TL;DR: The spatial distribution and temporal development of turbulent stresses downstream of the three investigated mechanical aortic valve prostheses correlated well with the superstructure of the valves.
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