In-Silico Analysis of the Influence of Pulmonary Vein Configuration on Left Atrial Haemodynamics and Thrombus Formation in a Large Cohort

Abstract

Atrial fibrillation (AF) is considered the most common human arrhythmia. Around 99% of thrombi in non-valvular AF are formed in the left atrial appendage (LAA). Studies suggest that abnormal LAA haemodynamics and the subsequently stagnated flow are the factors triggering clot formation. However, the relation between LAA morphology, the blood pattern and the triggering is not fully understood. Moreover, the impact of structures such as the pulmonary veins (PVs) on LA haemodynamics has not been thoroughly studied due to the difficulties of acquiring appropriate data. On the other hand, in-silico studies and flow simulations allow a thorough analysis of haemodynamics, analysing the 4D nature of blood flow patterns under different boundary conditions. However, the reduced number of cases reported on the literature of these studies has been a limitation. The main goal of this work was to study the influence of PVs on left atrium (LA) and LAA haemodynamics. Computational fluid dynamics simulations were run on 52 patients, the largest cohort so far in the literature, where different parameters were individually studied: pulmonary veins orientation and configuration; LAA and LA volumes and its ratio; and flow velocities. Our computational analysis showed how the right pulmonary vein height and angulation have a great influence on LA haemodynamics. Additionally, we found that LAA with great bending with its tip pointing towards the mitral valve could contribute to favour flow stagnation.

Joint Analysis of Morphological Parameters and In Silico Haemodynamics of the Left Atrial Appendage for Thrombogenic Risk Assessment

“…is study has focused on studying the influence of LA/ LAA morphology and in silico haemodynamics on thrombus formation before the implantation of a LAAO device, which can lead to a better patient selection and personalised therapy choice. However, the developed modelling pipeline to create haemodynamics simulations has also shown [17][18][19][20][21] to be useful in determining the formation of thrombus after the implantation of LAAO devices (i.e., device-related thrombus). Unfortunately, the required follow-up data to perform such verification were not available in the analysed patients in this study.…”

“…At this juncture, patientspecific models (e.g., digital twin concept [13]) based on computational fluid dynamics can provide a better haemodynamic characterization of the LA and LAA, deriving in silico indices describing blood flow at each point of the geometry over time. In the last decade, there have been several attempts to develop fluid simulation frameworks for the blood flow analysis of the human LA and LAA [14][15][16], but they have only been applied to a very limited number of patient-specific cases, except in a recent study with a cohort of simulated patients above fifty [17].…”

Sensitivity Analysis of In Silico Fluid Simulations to Predict Thrombus Formation after Left Atrial Appendage Occlusion

“…In the literature, some studies imposed LA deformation extracted from the processing of CT or MR images into the fluid simulations [16,17,20,21,25,29,30], while others developed advanced fluidstructure interaction models [14,24,31]. When dynamic medical images are not available, an interesting alternative is to use a dynamic mesh approach [27,28,33,34] with displacements generated either synthetically or from literature data.…”

“…Despite the mentioned limitations of ECAP and RRT indices, they were good descriptors of the overall LA haemodynamics that, combined with velocity magnitudes and blood flow recirculation analysis, can be used to assess the risk of DRT. The multifactorial analysis of haemodynamic simulations can contribute to identifying factors guiding LA blood flow patterns that are potentially important for DRT such as covering of the pulmonary ridge [45] or PV orientation [33]. For instance, Figure 6) shows that having the pulmonary ridge uncovered with the LAAO device (such as in Pat 1, red circle in the figure), or the presence of vortices (such as in Pat 3, pink arrow in the figure) is not necessarily linked to DRT if blood flow velocities are high in this area.…”

“…Most of these studies focused on analysing in silico haemodynamics parameters in the LAA in relation to thrombogenic risk, including explicit models of thrombus formation [26,29]. The influence of pulmonary vein configuration on blood flow patterns in the LA was also studied [15,19,31,33]. In addition, the effect of LAA closure has been modelled [14,23,28], the most advanced investigations having incorporated LAAO devices [22,28] and the relation thereof to DRT [27].…”