Fluid Mechanics of Heart Valves and Their Replacements

Abstract

As the pulsatile cardiac blood flow drives the heart valve leaflets to open and close, the flow in the vicinity of the valve resembles a pulsed jet through a nonaxisymmetric orifice with a dynamically changing area. As a result, three-dimensional vortex rings with intricate topology emerge that interact with the complex cardiac anatomy and give rise to shear layers, regions of recirculation, and flow instabilities that could ultimately lead to transition to turbulence. Such complex flow patterns, which are inherently valve- and patient-specific, lead to mechanical forces at scales that can cause blood cell damage and thrombosis, increasing the likelihood of stroke, and can trigger the pathogenesis of various life-threatening valvular heart diseases. We summarize the current understanding of flow phenomena induced by heart valves, discuss their linkage with disease pathways, and emphasize the research advances required to translate in-depth understanding of valvular hemodynamics into effective patient therapies.

Fluid‐structure interaction of a pulsatile flow with an aortic valve model: A combined experimental and numerical study

“…During the cardiac cycle, blood exerts a continuous loading on the aortic valve, which experiences compression, stretching, and bending stresses . Conversely, the interaction of the pulsatile blood flow with the valve flexible leaflets gives rise to complex flow structures in the vicinity of the valve, which could eventually lead to transition to turbulence . Assessing these complex structural and flow features could not only ultimately allow to improve the understanding of the degeneration process leading to aortic valve calcification but also drastically help the design of aortic valve prostheses.…”

Hemodynamic Performance and Thrombogenic Properties of a Superhydrophobic Bileaflet Mechanical Heart Valve

“…In this case, dissipation is likely associated with the complex vorticity structures seen downstream of the valve. These structures are described in more detail elsewhere 25, 76, 87 . Other methods involving passive flow control may alter these structures and could be combined with SH technology to improve performance 12, 26, 31, 54 .…”

“…Shear stress can also directly stimulate platelet activation in the absence of hemolysis, further promoting thrombo-embolic complications 1, 3, 8, 9, 38 . As a result of these risks, many studies have attempted to characterize shear stress and Reynolds shear stress (RSS) in MHVs through experimental and computational fluid dynamics 25, 34, 55, 76, 87 . Sotiropoulos et al provides a review of these dynamics and an explanation for how RSS can contribute to hemolysis or platelet activation by impacting the instantaneous shear stress experienced by blood cells is further explored in Morshed et al 59, 76 .…”

“…As a result of these risks, many studies have attempted to characterize shear stress and Reynolds shear stress (RSS) in MHVs through experimental and computational fluid dynamics 25, 34, 55, 76, 87 . Sotiropoulos et al provides a review of these dynamics and an explanation for how RSS can contribute to hemolysis or platelet activation by impacting the instantaneous shear stress experienced by blood cells is further explored in Morshed et al 59, 76 . Generally, these studies of RSS and shear stress find that stresses downstream of the bileaflet St. Jude valve remain below values that should induce hemolysis for MHVs.…”

A D-Shaped Bileaflet Bioprosthesis Which Replicates Physiological Left Ventricular Flow Patterns1

“…Although the well-established tri-leaflet design has been clinically proven to have long term durability [2] and low levels of thromboembolism [3], recent studies have suggested that the implantation of an artificial valve at the mitral position can significantly alter left ventricle flow field [4][5][6], as various parameters including valve geometry and orientation can have an effect on hemodynamics [7].…”