A computational study of blood flow in the left atrium of patients with atrial fibrillation
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Βάρσος, Παύλος
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Abstract
The main object of this Diploma Thesis is the computational study of blood flow in the left atrium of patients with Atrial Fibrillation. Atrial Fibrillation is the most frequent cardiac arrhythmia worldwide, since it affects 1 to 2% of the general population, while it is accompanied by high mortality rates. Like any other arrhythmia, Atrial Fibrillation refers to cases in which the electrical activity of the heart involves abnormalities, which are often not completely treated with neither medication nor surgery. A critical treatment method, minimally invasive, is catheter ablation which is simultaneously conducted with the procedure of electrophysiological mapping of the left atrium. The scope of this project is to create a framework for the comparison of mappings of multiple wall shear stress indices (which according to experiments are associated with the cardiac electrical activity) with electrophysiological mappings, using patient-specific data provided by doctors. Possible correlations can supply doctors with crucial information in a direction of improving the ablation process outcomes. Reconstruction techniques are implemented to convert two-dimensional MRI images into three-dimensional models of the left atrium. Following the optimization of the 3D model, the mesh generation and the solution of the cardiac flow procedures take place. Both of these processes are performed in the open-source software, OpenFOAM ®, as we take advantage of the countless capabilities offered. After generating the mesh, a procedure of paramount importance for a computational study, the mesh independence study is carried out under steady state conditions using the simpleFoam solver, aiming to obtain the most suitable model for the present project. At the same time, various turbulence models and boundary conditions are tested in order to detect any possible differences in blood flow behavior. Finally, a transient flow simulation of a realistic cardiac cycle is conducted, utilizing the pisoFoam solver, since our main goal is to visualize the distribution of a variety of hemodynamic parameters, such as the Oscillatory Shear Index, as well as indices for indicating blood stasis in high-risk areas of the left atrium, like the Left Atrial Appendage.
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Computational fluid dynamics (CFD), OpenFOAM, Wall shear stress, Atrial fibrillation, Hemodynamics