Understanding the role of the left atrial appendage on the flow in the atrium

Background: The exclusion/occlusion of the left atrial appendage (LAA) is a treatment option for atrial fibrillation (AF) patients who are at high risk of stroke and high risk of bleeding. As the role of the LAA is not well understood or explored, this study aims to assess its role on flow dynamics in the left atrium. Methods: Computational fluid dynamics (CFD) simulations were carried out for nine AF patients before and after LAA exclusion. The flow parameters investigated included the LA velocities, Time Averaged Wall Shear Stress (TAWSS), Oscillatory Shear Index (OSI), Relative Residence Time (RRT), and Pressure in the LA. Results: This study shows that, on average, a decrease in TAWSS (1.82 +/- 1.85 Pa to 1.27 +/- 0.96 Pa, p < 0.05) and a slight increase in OSI (0.16 +/- 0.10 to 0.17 +/- 0.10, p < 0.05), RRT (1.87 +/- 1.84 Pa-1 to 2.11 +/- 1.78 Pa-1, p < 0.05), and pressure (-19.2 +/- 6.8 mmHg to -15.3 +/- 8.3 mmHg, p < 0.05) were observed in the LA after the exclusion of the LAA, with a decrease in low-magnitude velocities. Conclusion: The exclusion of the LAA seems to be associated with changes in LA flow dynamics. Further studies are needed to elucidate the clinical implications of these changes.