Image-Guided Fluid-Structure Interaction Simulation of Transvalvular Hemodynamics: Quantifying the Effects of Varying Aortic Valve Leaflet Thickness

Abstract

When flow-induced forces are altered at the blood vessel, maladaptive remodeling can occur. One reason such remodeling may occur has to do with the abnormal functioning of the aortic heart valve due to disease, calcification, injury, or an improperly-designed prosthetic valve, which restricts the opening of the valve leaflets and drastically alters the hemodynamics in the ascending aorta. While the specifics underlying the fundamental mechanisms leading to changes in heart valve function may differ from one cause to another, one common and important change is in leaflet stiffness and/or mass. Here, we examine the link between valve stiffness and mass and the hemodynamic environment in aorta by coupling magnetic resonance imaging (MRI) with high-resolution fluid-structure interaction (FSI) computational fluid dynamics to simulate blood flow in a patient-specific model. The thoracic aorta and a native aortic valve were re-constructed in the FSI model from the MRI data and used for the simulations. The effect of valve stiffness and mass is parametrically investigated by varying the thickness (h) of the leaflets (h = 0.6, 2, 4 mm). The FSI simulations were designed to investigate systematically progressively higher levels of valve stiffness by increasing valve thickness and quantifying hemodynamic parameters known to be linked to aortopathy and valve disease. The computed results reveal dramatic differences in all hemodynamic parameters: (1) the geometric orifice area (GOA), (2) the maximum velocity V max of the jet passing through the aortic orifice area, (3) the rate of energy dissipationĖ diss (t), (4) the total loss of energy E diss , (5) the kinetic energy of the blood flow E kin (t), and (6) the average magnitude of vorticity Ω a (t), illustrating the change in hemodynamics that occur due to the presence of aortic valve stenosis.

Analysis of Turbulence Effects in a Patient-Specific Aorta with Aortic Valve Stenosis

“…At similar stroke volumes and heart rates to the current study, they observed net energy losses on the order of ~ 0.09 J and ~ 0.2 to 0.3 J for their mild and moderate stenosis cases, respectively. Our values for net energy loss and viscous dissipation are of similar magnitudes to those reported in literature, 18 , 47 despite differences in methods. Previous studies have estimated either the viscous, turbulent or total dissipation and/or energy losses in aortic flows, but none have quantified the individual contributions from viscous and turbulent dissipation—a key step in understanding not only the net effect of aortic valve disease on energy loss but also the isolated effects of turbulence on energy loss.…”

“…There have been studies which estimate either viscous 5 , 18 , 27 or turbulent 20 energy losses from 4D flow MRI data or numerical simulation in aortic and idealised flows. Gilmanov et al 18 conducted patient-specific fluid-structure interaction simulations of calcified aortic valves.…”

“…There have been studies which estimate either viscous 5 , 18 , 27 or turbulent 20 energy losses from 4D flow MRI data or numerical simulation in aortic and idealised flows. Gilmanov et al 18 conducted patient-specific fluid-structure interaction simulations of calcified aortic valves. In the valve with a high degree of calcification; which obstructs the effective valve orifice area producing aortic flows similar to AVS, a peak viscous dissipation of ~ 0.17 W was observed which is of similar magnitude to the peak viscous dissipation in this study (0.23 W).…”

Pressure distribution over the leaflets and effect of bending stiffness on fluid–structure interaction of the aortic valve

“…In general, there has been limited study about the effect of the bending stiffness of the leaflets and how it affects the FSI of heart valves. One exception is a recent computational study (Gilmanov et al 2019), in which the authors performed FSI simulations of a patient-specific aortic model with varying leaflet thickness and studied the effect of the bending rigidity on the valve's opening area, flow speed and kinetic energy. However, the pressure distribution and valve force were not discussed.…”

Finite element analysis in the modeling of the heart and aorta structures

“…наук, профессор, чл.-корр. РАН, заведующий кафедрой терапии факультета усовершенствования врачей 3 ; первый заместитель генерального директора, заместитель генерального директора по научной работе 4 ; ORCID: https://orcid.org/0000-0001-9481-9639 Борисова Екатерина Викторовна -д-р мед. наук, ст.…”