Analysis of a coupled fluid‐structure interaction model of the left atrium and mitral valve

Abstract

We present a coupled left atrium‐mitral valve model based on computed tomography scans with fibre‐reinforced hyperelastic materials. Fluid‐structure interaction is realised by using an immersed boundary‐finite element framework. Effects of pathological conditions, eg, mitral valve regurgitation and atrial fibrillation, and geometric and structural variations, namely, uniform vs non‐uniform atrial wall thickness and rule‐based vs atlas‐based fibre architectures, on the system are investigated. We show that in the case of atrial fibrillation, pulmonary venous flow reversal at late diastole disappears, and the filling waves at the left atrial appendage orifice during systole have reduced magnitude. In the case of mitral regurgitation, a higher atrial pressure and disturbed flows are seen, especially during systole, when a large regurgitant jet can be found with the suppressed pulmonary venous flow. We also show that both the rule‐based and atlas‐based fibre defining methods lead to similar flow fields and atrial wall deformations. However, the changes in wall thickness from non‐uniform to uniform tend to underestimate the atrial deformation. Using a uniform but thickened wall also lowers the overall strain level. The flow velocity within the left atrial appendage, which is important in terms of appendage thrombosis, increases with the thickness of the left atrial wall. Energy analysis shows that the kinetic and dissipation energies of the flow within the left atrium are altered differently by atrial fibrillation and mitral valve regurgitation, providing a useful indication of the atrial performance in pathological situations.

Demonstration of Patient-Specific Simulations to Assess Left Atrial Appendage Thrombogenesis Risk

“…Several CFD studies have explored the effect of LAA geometry on blood flow but, taken together, have offered ambiguous results. Bosi et al (2018) found that LAA morphologies that are clinically associated with higher stroke incidence have impaired blood washout, whereas other studies (Garcia-Isla et al, 2018;Feng et al, 2019;Masci et al, 2019) reported that LAA stasis depends critically on additional factors such as PV inflow patterns.…”

A poroelastic immersed finite element framework for modelling cardiac perfusion and fluid–structure interaction

“…IFE further avoids the use of body‐conforming discretizations between the fluid and structure, 17 and hence overcomes mesh distortion issues in body‐fitted approaches 18,19 . One such an example is shown in simulations of FSI in the vicinity of the cardiac valves 20,21 …”

“…18,19 One such an example is shown in simulations of FSI in the vicinity of the cardiac valves. 20,21 The extension of IFE formulations to treat poroelastic structures is relatively recent. 22,23 Strychalski et al 22 developed a poroelastic IB method for cellular mechanics, using a Lagrangian reference frame while the fluid moving both in and outside of the cell is described in Eulerian form although this approach only considers the dilute limit.…”

Image-based computational hemodynamics analysis of systolic obstruction in hypertrophic cardiomyopathy

“…In this regard, two main standpoints are currently adopted: Fluid-Structure Interaction (FSI) simulations and prescribed-motion Computational Fluid Dynamics (CFD). The first approach, employed for example in [6], [7], [8], [9], [10], [11], consists in the coupled solution of the fluid dynamics of blood flow and of the structure mechanics of the myocardium and valves, thus entailing a possibly very high computational cost. On the other hand, in image-based CFD, the displacement of the myocardium and valves leaflets is reconstructed from kinetic medical images and then prescribed as endocardial data to obtain the fluid domain configuration.…”