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Your search keyword '"Vergara, Christian"' showing total 291 results
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291 results on '"Vergara, Christian"'

27. A mathematical model to assess the effects of COVID-19 on the cardiocirculatory system.

Author

Tonini, Andrea, Vergara, Christian, Regazzoni, Francesco, Dede', Luca, Scrofani, Roberto, Cogliati, Chiara, and Quarteroni, Alfio

Subjects
*MATHEMATICAL models, *SYSTOLIC blood pressure, *COVID-19, *PULMONARY circulation, *CARDIOVASCULAR system, *HEART, *CAPILLARIES
Abstract

Impaired cardiac function has been described as a frequent complication of COVID-19-related pneumonia. To investigate possible underlying mechanisms, we represented the cardiovascular system by means of a lumped-parameter 0D mathematical model. The model was calibrated using clinical data, recorded in 58 patients hospitalized for COVID-19-related pneumonia, to make it patient-specific and to compute model outputs of clinical interest related to the cardiocirculatory system. We assessed, for each patient with a successful calibration, the statistical reliability of model outputs estimating the uncertainty intervals. Then, we performed a statistical analysis to compare healthy ranges and mean values (over patients) of reliable model outputs to determine which were significantly altered in COVID-19-related pneumonia. Our results showed significant increases in right ventricular systolic pressure, diastolic and mean pulmonary arterial pressure, and capillary wedge pressure. Instead, physical quantities related to the systemic circulation were not significantly altered. Remarkably, statistical analyses made on raw clinical data, without the support of a mathematical model, were unable to detect the effects of COVID-19-related pneumonia in pulmonary circulation, thus suggesting that the use of a calibrated 0D mathematical model to describe the cardiocirculatory system is an effective tool to investigate the impairments of the cardiocirculatory system associated with COVID-19. [ABSTRACT FROM AUTHOR]

Published
2024
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40. A stable loosely-coupled scheme for cardiac electro-fluid-structure interaction

Author

Bucelli, Michele, Gabriel, Martin Geraint, Gigante, Giacomo, Quarteroni, Alfio, and Vergara, Christian

Subjects
Cardiac modeling, Multiphysics, Electromechanics, Fluid-structure interaction, Robin-Neumann interface conditions, Settore MAT/08 - Analisi Numerica, Settore MAT/05 - Analisi Matematica, FOS: Mathematics, Numerical Analysis (math.NA), Mathematics - Numerical Analysis
Abstract

We present a loosely coupled scheme for the numerical simulation of the cardiac electro-fluid-structure interaction problem, whose solution is typically computationally intensive due to the need to suitably treat the coupling of the different submodels. Our scheme relies on a segregated treatment of the subproblems, in particular on an explicit Robin-Neumann algorithm for the fluid-structure interaction, aiming at reducing the computational burden of numerical simulations. The results, both in an ideal and a realistic cardiac setting, show that the proposed scheme is stable at the regimes typical of cardiac simulations. From a comparison with a scheme with implicit fluid-structure interaction, it emerges that, while conservation properties are not fully preserved, computational times significantly benefit from the explicit scheme. Overall, the explicit discretization represents a good trade-off between accuracy and cost, and is a valuable alternative to implicit schemes for fast large-scale simulations.

Published
2022

42. Fluid‐structure interaction analysis of transcatheter aortic valve implantation.

Author

Fumagalli, Ivan, Polidori, Rebecca, Renzi, Francesca, Fusini, Laura, Quarteroni, Alfio, Pontone, Gianluca, and Vergara, Christian

Subjects
HEART valve prosthesis implantation, FLUID-structure interaction, AORTIC stenosis, PROSTHETICS, MECHANICAL hearts, BLOOD flow, SHEAR walls, DEEP brain stimulation
Abstract

Transcatheter aortic valve implantation (TAVI) is a minimally invasive intervention for the treatment of severe aortic valve stenosis. The main cause of failure is the structural deterioration of the implanted prosthetic leaflets, possibly inducing a valvular re‐stenosis 5–10 years after the implantation. Based solely on pre‐implantation data, the aim of this work is to identify fluid‐dynamics and structural indices that may predict the possible valvular deterioration, in order to assist the clinicians in the decision‐making phase and in the intervention design. Patient‐specific, pre‐implantation geometries of the aortic root, the ascending aorta, and the native valvular calcifications were reconstructed from computed tomography images. The stent of the prosthesis was modeled as a hollow cylinder and virtually implanted in the reconstructed domain. The fluid‐structure interaction between the blood flow, the stent, and the residual native tissue surrounding the prosthesis was simulated by a computational solver with suitable boundary conditions. Hemodynamical and structural indicators were analyzed for five different patients that underwent TAVI – three with prosthetic valve degeneration and two without degeneration – and the comparison of the results showed a correlation between the leaflets' structural degeneration and the wall shear stress distribution on the proximal aortic wall. This investigation represents a first step towards computational predictive analysis of TAVI degeneration, based on pre‐implantation data and without requiring additional peri‐operative or follow‐up information. Indeed, being able to identify patients more likely to experience degeneration after TAVI may help to schedule a patient‐specific timing of follow‐up. [ABSTRACT FROM AUTHOR]

Published
2023
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