A fluid–structure interaction model of the aortic valve with coaptation and compliant aortic root

Abstract

While aortic valve root compliance and leaflet coaptation have significant influence on valve closure, their implications have not yet been fully evaluated. The present study developed a full fluid-structure interaction (FSI) model that is able to cope with arbitrary coaptation between the leaflets of the aortic valve during the closing phase. Two simplifications were also evaluated for the simulation of the closing phase only. One employs an FSI model with a rigid root and the other uses a "dry" (without flow) model. Numerical tests were performed to verify the model. New metrics were defined to process the results in terms of leaflet coaptation area and contact pressure. The axial displacement of the leaflets, closure time and coaptation parameters were similar in the two FSI models, whereas the dry model, with imposed uniform load on the leaflets, produced larger coaptation area and contact pressure, larger axial displacement and faster closure time compared with the FSI model. The differences were up to 30% in the coaptation area, 55% in the contact pressure and 170% in the closure time. Consequently, an FSI model should be used to accurately resolve the kinematics of the aortic valve and leaflet coaptation details during the end-closing stage.

Aortic Valve Geometry Modeling – Review

“…De Hart et al [38] despite that the purpose of research is to analyze the impact on the structural stress state and the associated fluid dynamical flow, the aortic valve leaflets are assumed to behave linear elastic and isotropic. Marom et al [46,47] the choice of an isotropic and linear elastic leaflet tissue material properties justify the purpose of conducted simulation, ie. modeling the evolving nonlinear contact mechanism between the valve leaflet.…”

Fluid–Structure Interaction Simulation of Aortic Valve Closure with Various Sinotubular Junction and Sinus Diameters

“…A constant thickness of 0.6 mm (T 1 = 0.6) is used for the sinus and ventricular outflow tract and the initial tract of the ascending aorta, while a thickness of the valvular leaflets is considered 0.3 mm. 9 (T 2 = 0.3) Two straight rigid and circular tubes with lengths of 20 and 50 mm, respectively, were added upstream and downstream, to move the boundary conditions away from the regions of interest. The 2D geometries of the fluid were created in SolidWorks (SolidWorks, Concord, MA).…”

“…In the 2D models, a Poisson's ratio of 0.45, Young's modulus of 1E6 Pa and 2E6 Pa, and density of 1100 and 2000 kg/m 3 were used for the leaflets and the root, respectively. 9,11 Resolve Method A hemodynamic analysis using FSI method was performed in order to delineate important flow features emanating from the various simulated aortic root geometries. We adopted the direct computing of twoway coupling.…”

“…8 Computational simulations of aortic valve allow analysis of complex systems and quantification of the effects of changes in one or more of the parameters (e.g., geometrical dimensions or mechanical properties) characterizing the system of interest. 9 This capability makes computational modeling a powerful tool for analyzing the aortic root. Marom developed a full fluid structure interaction (FSI) model dealing with coaptation within physiological conditions 9 and used the FSI model to determine the influence of changes in aortic annulus diameter (DAA) on the geometry and dynamics of the aortic root and valve cusps.…”

“…9 This capability makes computational modeling a powerful tool for analyzing the aortic root. Marom developed a full fluid structure interaction (FSI) model dealing with coaptation within physiological conditions 9 and used the FSI model to determine the influence of changes in aortic annulus diameter (DAA) on the geometry and dynamics of the aortic root and valve cusps. 11 Monica Soncini extended the biomechanical analysis of the David (cylindrical graft) and Yacoub (ascalloped graft) techniques via finite element modeling of the entire cardiac cycle.…”