Computational study of the left atrial blood flow and wall mechanics with a healthy, diseased and repaired mitral valve

The left atrium (LA) is an important chamber of the heart, where the left atrial appendage (LAA) is situated. The LAA is a finger-like extension that develops in the third week of gestation: it is the most prevalent region for thrombosis in atrial fibrillation (AF). It has been investigated how the backflow into the LA affects the filling of the LA. It is the scientific goal of this project to analyze and characterize the flow structures and stresses in the bulk of the flow and at the atrial wall as well as the atrial motion and deformation during the atrium filling phase in the two cases. Major differences were found in the atrial wall displacement between the two cases, where the MR geometry showed a significant deformation. The LAA in the MR case is characterized by high displacement values, differently from the physiological case. In particular, the average displacement in the MR case does not have a peak: it shows a continuous increase. The WSS magnitude was studied in both cases, showing major differences in values and behavior over time. In the physiological case, the WSS magnitude is half the pathological case one. The other difference can be found in the behavior of the WSS magnitude over time: it does not have a clear peak in the pathological case, but it continues to increase over time. For the bulk flow, the LNH has been used to evaluate the helical structures of the blood, showing that the geometries are characterized by helical structures during the whole simulation. The results obtained showed different behaviors between physiological and pathological cases, emphasizing the role of the regurgitant jet on the hemodynamic in the LA and LAA. These findings could be used to understand the differences in the flow and in the atrial wall mechanics due to the implantation of a repairing device such as the MitraClip, which is used to repair the mitral valve and restore the mitral leaflets coaptation.