Development of a Computational Fluid Dynamics Model of the Left Atrium in Atrial Fibrillation on a Patient Specific Basis

Purpose: Morphological and functional remodeling of the left atrium (LA) caused by atrial fibrillation (AF) favors blood stasis and, consequently, stroke risk. Several clinical studies suggest that stroke risk stratification could be improved by using hemodynamic information on the LAand the left atrial appendage (LAA). The goal of this study was to develop a patient-specific computational fluid dynamics model (CFD) of the LA which may help quantify the hemodynamic implications of AF on a patient-specific basis. Methods: Specifically designed algorithms were applied to derive the 3D patient specific LA anatomical model and the LA motion field throughout the cardiac cycle from dynamic CT imaging in two patients with persistent AF. To perform CFD simulation in the LA, the arbitrary Lagrangian Eulerian formulation of the Navier-Stokes equations was applied in both sinus rhythm (SR) and AF conditions. The CFD model was constrained by assigning realistic inflow boundary conditions obtained from real Doppler measurements in AF patients. Results: Simulated velocity profile at the mitral valve showed a “physiological” behavior with amplitude compatible with AF condition. Moreover, in the SR simulation, peak A-wave velocity was 38 cmˑs-1 while the A-wave was absent in AF. LAA blood flow stasis was quantified by counting the number of particles remaining in the LAA throughout the cardiac cycles. After three cardiac cycles, 26% of the particles remained in the LAA in the SR condition, while 45.6% of them remained in the LAA in the AF condition. Conclusion: We presented our initial efforts towards the development of a patient specific CFD model of AF. To our knowledge, this is the first presented in literature. The model returned realistic blood flow patterns both at SR and during AF. In addition, it confirmed that AF episodes result in a reduced washout of the LAA which might lead to thrombi formation.