Sensitivity analysis of geometrical parameters to study haemodynamics and thrombus formation in the left atrial appendage

Abstract

The left atrial appendage (LAA) is a complex and heterogeneous protruding structure of the left atrium (LA). In atrial fibrillation patients, it is the location where 90% of the thrombi are formed. However, the role of the LAA in thrombus formation is not fully known yet. The main goal of this work is to perform a sensitivity analysis to identify the most relevant LA and LAA morphological parameters in atrial blood flow dynamics. Simulations were run on synthetic ellipsoidal left atria models where different parameters were individually studied: pulmonary veins and mitral valve dimensions; LAA shape; and LA volume. Our computational analysis confirmed the relation between large LAA ostia, low blood flow velocities and thrombus formation. Additionally, we found that pulmonary vein configuration exerted a critical influence on LAA blood flow patterns. These findings contribute to a better understanding of the LAA and to support clinical decisions for atrial fibrillation patients.

Demonstration of Patient-Specific Simulations To Assess Left Atrial Appendage Thrombogenesis Risk

“…Taken together, our results indicate that flow patterns inside the LAA are not as complex as in the LA body or the LV, which we attribute to the strong geometrical confinement of the flow inside the appendage. These flow patterns led to elevated blood residence in the LAA compared to the LA body, in agreement with previous CFD results [3,8,15,18,19,22], and the consensus that thrombi form preferentially in the LAA. Patients with impaired atrial function also showed a trend for blood stasis to appear near the mitral annulus, since their weaker LA body vortex systems caused decreased stirring compared to normals.…”

“…Similar to previous simulations [3,8,15,18,22], our LA model did not consider the mitral valve in the outflow of the chamber. This choice is justified by whole left heart CFD studies showing that the mitral valve does not significantly affect LA flow [28].…”

“…This choice is justified by whole left heart CFD studies showing that the mitral valve does not significantly affect LA flow [28]. Our work improves over most previous computational studies of the LA flow [3,8,18] by considering patient-specific inflow/outflow boundary conditions, similar to Otani et al [22]. One limitation of our simulations is that PV flow rates were evenly distributed [16].…”

“…The rationale for including fixedwall simulations in our study was to assess how these limitations affect the prediction of patientspecific hemodynamic parameters such as residence time, by comparing with moving-wall simulations. This assessment is warranted considering that several previous studies used fixedwall simulations [3,8].…”

“…Several CFD studies have explored the effect of LAA geometry on blood flow but, taken together, have offered ambiguous results. Bosi et al [3] found that LAA morphologies that are clinically associated with higher stroke incidence have impaired blood washout, whereas other studies [8,19] reported that LAA stasis depends critically on additional factors such as PV inflow patterns.…”