Computational modeling of hemodynamics and blood washout in the patient-specific left atrial appendages

The left atrial appendage (LAA) is a small chamber-like organ connected to the left atrium (LA). Studies have shown that this structure is implicated in thrombus formation and thromboembolic events for patients with atrial fibrillations. However, due to its highly complex and variable shape, the blood flow patterns and the mechanism of thrombogenesis inside the LAA are poorly understood. The aim of this study is to analyze the hemodynamics inside patient-specific LA/LAAs via computational fluid dynamics (CFD) modeling and to understand the potential for thrombus formation in the LAA. Patient-specific LA/LAA geometries are derived from high-resolution CT scans and the blood flowrate profiles at the mitral annulus are obtained from ultrasound Doppler measurements. Direct numerical simulation is carried out using a sharp-interface immersed boundary method. An Eulerian transport equation for the blood residence time is also solved inside the fluid domain to investigate the blood transportation and coagulation potential in the LAA. In this study, several patient-specific cases with different LAA shapes and heart conditions are considered and the blood flow patterns and washout in the LAA are compared for these cases.