arXiv subjects

Conrado Ferrera

Publications and source records attributed to Conrado Ferrera.

3 recordsLinked to original sources

arXiv2024

Morphing the left atrium geometry: The role of the pulmonary veins on flow patterns and thrombus formation

Background: Despite the significant advances made in the field of computational fluid dynamics (CFD) to simulate the left atrium (LA) in atrial fibrillation (AF) conditions, the connection between atrial structure, flow dynamics, and blood stagnation in the left atrial appendage (LAA) remains unclear. Deepening our understanding of this relationship would have important clinical implications, as the thrombi formed within the LAA are one of the main causes of stroke. Aim: To highlight and better understand the fundamental role of the PV orientation in forming atrial flow patterns and systematically quantifying its effect on blood stasis within the LAA. Methods: Two patients with opposite atrial flow patterns were selected for the study. The atria were segmented and subsequently morphed to modify the pulmonary vein (PV) orientations in a highly controlled manner. CFD analysis were performed using a kinematic model able to reproduce AF conditions. Results were projected into the universal left atrial appendage coordinate (ULAAC) system to enhance data visualization and comparison. Results: The position of the main atrial vortex can be modified by controlled changes in the PV orientations, which to the best of our knowledge was not demonstrated before. This finding may have important clinical implications, as the behavior and position of the main atrial vortex is crucial to define the LA flow patterns and thus the LAA washing, making possible to assess the stroke risk for a particular patient.

physics.med-ph↗

arXiv2024

Influence of the flow split ratio on the position of the main atrial vortex: implications for stasis on the left atrial appendage

Background: Despite the recent advances in computational fluid dynamics (CFD) techniques applied to blood flow within the left atrium (LA), the relationship between atrial geometry, flow patterns, and blood stasis within the left atrial appendage (LAA) remains unclear. A better understanding of this relationship would have important clinical implications, as thrombi originating in the LAA are a common cause of stroke in patients with atrial fibrillation (AF). Aim: To identify the most representative atrial flow patterns on a patient-specific basis and study their influence on LAA blood stasis by varying the flow split ratio and some common atrial modeling assumptions. Methods: Three recent techniques were applied to nine patient-specific computational fluid dynamics (CFD) models of patients with AF: a kinematic atrial model to isolate the influence of wall motion because of AF, projection on a universal LAA coordinate system, and quantification of stagnant blood volume (SBV). Results: We identified three different atrial flow patterns based on the position of the center of the main circulatory flow. The results also illustrate how atrial flow patterns are highly affected by the flow split ratio, increasing the SBV within the LAA. As the flow split ratio is determined by the patient's lying position, the results suggest that the most frequent position adopted while sleeping may have implications for the medium- and long-term risks of stroke.

physics.med-ph↗

arXiv2023

Reduced-order models of wall shear stress patterns in the left atrial appendage from a data-augmented atrial database

Background: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting over 1% of the population. It is usually triggered by irregular electrical impulses that cause the atria to contract irregularly and ineffectively. It increases blood stasis and the risk of thrombus formation within the left atrial appendage (LAA) and aggravates adverse atrial remodeling. Despite recent efforts, LAA flow patterns representative of AF conditions and their association with LAA stasis remain poorly characterized. Aim: To develop reduced-order data-driven models of LAA flow patterns during atrial remodeling in order to uncover flow disturbances concurrent with LAA stasis that could add granularity to clinical decision criteria. Methods: We combined a geometric data augmentation process with projection of results from 180 CFD atrial simulations on a universal LAA coordinate (ULAAC) system. The projection approach enhances data visualization and facilitates direct comparison between different anatomical and functional states. ULAAC projections were used as input for a proper orthogonal decomposition (POD) algorithm to build reduced-order models of hemodynamic metrics, extracting flow characteristics associated with AF and non-AF anatomies. Results: We verified that the ULAAC system provides an adequate representation to visualize data distributions on the LAA surface and to build POD-based reduced-order models. These models revealed significant differences in LAA flow patterns for atrial geometries that underwent adverse atrial remodeling and experienced elevated blood stasis. Together with anatomical morphing-based patient-specific data augmentation, this approach could facilitate data-driven analyses to identify flow features associated with thrombosis risk due to atrial remodeling.

physics.med-ph↗