17 Giugno 2022. Seminari fra Giovani Ricercatori
Seminari fra Giovani Ricercatori.
“A proof-of-concept study to develop a numerical model of the left atrial appendage occlusion”
by Francesca Danielli (PhD Student @ Laboratory of Biological Structure Mechanics, Department of Chemistry, Materials and Chemical Engineering “Giulio Natta”, Politecnico di Milano)
“A computational fluid dynamics workflow for the assessment of thromboembolic risk in non-valvular atrial fibrillation patients”
By Emanuele Gasparotti and Benigno Marco Fanni (PhD Students @ BioCardioLab, Bioengineering Unit, Heart Hospital G. Pasquinucci, Fondazione Toscana Gabriele Monasterio)
Left Atrial Appendage Occlusion (LAAO) with Nitinol devices is a percutaneous procedure to prevent thrombus formation generating over 90% in left atriums affected by atrial fibrillation. Real-world clinical outcomes proved how LAAO is a non-inferior alternative to oral anticoagulants. Nonetheless, the LAA morphological complexity hinders the overall procedure (e.g. device sizing and positioning). In this regard, Finite Element (FE) modeling is a robust tool in guiding clinical decisions. To date, the works available in the literature on FE modeling of LAAO define the optimal device positioning without providing evidence about a thorough investigation of the crucial features affecting the outcome of the procedure. Furthermore, FE models of the devices are used in complex patient-specific simulations without any preliminary validation.
The current study proposes a comprehensive approach to build a FE model of LAAO, including virtual models of both the device and the anatomical site. Currently, the workflow of the study involves the following steps: (i) development of a validated FE model of a commercial occlusion device; (ii) development of a numerical model of a patient-specific anatomy; (iii) discussion of the model uncertainties, investigating the influence of anatomical features (e.g. wall thickness and elastic modulus) on the outcome of the procedure (LAAO).
The left atrial appendage (LAA) is a complex cardiovascular structure which can yield to thrombi formation in patients with non-valvular atrial fibrillation (AF). The study of LAA fluid dynamics together with morphological features should be investigated in order to evaluate the possible connections of geometrical and hemodynamics indices with the stroke risk. In fact, the morphology of the LAA is quite variable and it is commonly classified into different main shape classes. In non-valvular AF patients, the normal contractility of LAA is reduced, resulting in a high decreasing of velocity and, consequently, in a higher risk of clotting formation due to the hemostasis of the blood inside the LAA. Moreover, the changes in LAA position and morphology during cardiac cycle due to the atrium motion are significant aspects to be considered in the LAA geometrical evaluation. In this context, computational fluid dynamics (CFD) simulations represent a powerful tool to investigate patient-specific LAA hemodynamics and morphology in AF conditions. Moreover, post-operative outcomes need crucially evaluation to quantify residual leakage after LAA closure intervention. Hence, CFD can be exploited also to evaluate possible residual risk of thrombi generation even after LAAO, due to the mutual effect of complex LAA anatomy and implanted device size/type. In the present CFD study we investigated both pre-operative and post-operative conditions. First, the hemodynamics implications of the different LAA morphologies were analyzed, to identify the anatomy with higher risk of clotting formation. Analogously, the effect of pulmonary veins conformation on the overall LAA fluid dynamics was also evaluated, to increase the value of risk stratification. Finally, considering the post-operative condition, the evaluation of the residual stroke risk after the LAAO was conducted.