Impact of Atrial Fibrillation on Left Atrium Haemodynamics: A Computational Fluid Dynamics Study

Abstract

We analyze left atrium haemodynamics, highlighting differences among healthy individuals and patients affected by atrial fibrillation. The computational study is based on patient-specific geometries of the left atria to simulate blood flow dynamics. We devise a novel procedure aimed at recovering the boundary conditions for the 3D haemodynamics simulations, particularly useful in absence of specific ones provided by clinical measurements. With this aim, we introduce a parametric definition of the atria displacement, and we employ a closed-loop lumped parameter model of the whole cardiocirculatory system conveniently tuned on the basis of the patient characteristics. We evaluate a number of fluid dynamics indicators for the atrial haemodynamics, validating our numerical results in terms of several clinical measurements; we investigate the impact of geometrical and clinical features on the risk of thrombosis. To analyse the correlation of thrombus formation with atrial fibrillation, coherently with the medical evidence, we propose a novel indicator, which we call age stasis and that arises from the combination of Eulerian and Lagrangian quantities. This indicator identifies regions where the slow flow cannot rinse the chamber properly, accumulating stale blood particles and creating optimal conditions for clot formation.

A geometric multiscale model for the numerical simulation of blood flow in the human left heart

“…In cardiac FSI problems, the fluid model is coupled with an electromechanics (EM) model and the coupling is explicitly solved, entailing a high computational effort [85,83,44,84,21,36,18,66,65]. In prescribed displacement CFD simulations, on the other hand, the influence of the cardiac walls motion is modeled by analytical laws [71,24,70,88,26,12,87,39,23], by patient-specific image-based reconstructions [35,76,20,52,50,51], or via the displacement field computed from a previous EM simulation [11,44,75].…”