BUSCADOR RECOLECTA

Background and objective: in this work, the analysis of the importance of hemodynamic updates on a mechanobiological model of atheroma plaque formation is proposed. Methods: for that, we use an idealized and axisymmetric model of carotid artery. In addition, the behavior of endothelial cells depending on hemodynamical changes is analyzed too. A total of three computational simulations are carried out and their results are compared: an uncoupled model and two models that consider the opposite behavior of endothelial cells caused by hemodynamic changes. The model considers transient blood flow using the Navier-Stokes equation. Plasma flow across the endothelium is determined with Darcy's law and the Kedem-Katchalsky equations, considering the three-pore model, which is also employed for the flow of substances across the endothelium. The behavior of the considered substances in the arterial wall is modeled with convection¿diffusion¿reaction equations, and the arterial wall is modeled as a hyperelastic Yeoh's material. Results: significant variations are noted in both the morphology and stenosis ratio of the plaques when comparing the uncoupled model to the two models incorporating updates for geometry and hemodynamic stimuli. Besides, the phenomenon of double-stenosis is naturally reproduced in the models that consider both geometric and hemodynamical changes due to plaque growth, whereas it cannot be predicted in the uncoupled model. Conclusions: the findings indicate that integrating the plaque growth model with geometric and hemodynamic settings is essential in determining the ultimate shape and dimensions of the carotid plaque., Support was obtained from the Spanish Ministry of Science and Technology through the research projects PID2019-107517RB-I00 and PID2022-140219OB-I00 and financial support to P. Hernández-López from the grant BES-2017-080239, and the regional Government of Aragón support for the funding of the research project T24-20R. Myriam Cilla is supported by Grant Ramón Cajal grant 171562 funded by MICIU/AEI/ 10.13039/501100011033 and the European Social Fund Plus (FSE+) . M. Malvé is supported by grant PID2021-125731OB-C31 from the Spanish Ministry of Science and Innovation MCIN/AEI/10.13039/501100011033/ and FEDER ("Away to build Europe").; The authors thank the research support from the CIBER initiative, whose actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund .

Atherosclerosis is a prevalent cause of acute coronary syndromes that consists of lipid deposition inside the artery wall, creating an atherosclerotic plaque. Early detection may prevent the risk of plaque rupture. Nowadays, intravascular ultrasound (IVUS) is the most common medical imaging technology for atherosclerotic plaque detection. It provides an image of the section of the coronary wall and, in combination with new techniques, can estimate the displacement or strain fields. From these magnitudes and by inverse analysis, it is possible to estimate the mechanical properties of the plaque tissues and their stress distribution. In this paper, we presented a methodology based on two approaches to characterize the mechanical properties of atherosclerotic tissues. The first approach estimated the linear behavior under particular pressure. In contrast, the second technique yielded the non-linear hyperelastic material curves for the fibrotic tissues across the complete physiological pressure range. To establish and validate this method, the theoretical framework employed in silico models to simulate atherosclerotic plaques and their IVUS data. We analyzed different materials and real geometries with finite element (FE) models. After the segmentation of the fibrotic, calcification, and lipid tissues, an inverse FE analysis was performed to estimate the mechanical response of the tissues. Both approaches employed an optimization process to obtain the mechanical properties by minimizing the error between the radial strains obtained from the simulated IVUS and those achieved in each iteration. The second methodology was successfully applied to five distinct real geometries and four different fibrotic tissues, getting median R2 of 0.97 and 0.92, respectively, when comparing the real and estimated behavior curves. In addition, the last technique reduced errors in the estimated plaque strain field by more than 20% during the optimization process, compared to the former approach. The findings enabled the estimation of the stress field over the hyperelastic plaque tissues, providing valuable insights into its risk of rupture.

This study explored the impact of hypertension on atheroma plaque formation through a mechanobiological model. The model incorporates blood flow via the Navier–Stokes equation. Plasma flow through the endothelium is determined by Darcy’s law and the Kedem–Katchalsky equations, which consider the three-pore model utilized for substance flow across the endothelium. The behaviour of these substances within the arterial wall is described by convection–diffusion–reaction equations, while the arterial wall itself is modelled as a hyperelastic material using Yeoh’s model. To accurately evaluate hypertension’s influence, adjustments were made to incorporate wall compression-induced wall compaction by radial compression. This compaction impacts three key variables of the transport phenomena: diffusion, porosity, and permeability. Based on the obtained findings, we can conclude that hypertension significantly augments plaque growth, leading to an over 400% increase in plaque thickness. This effect persists regardless of whether wall mechanics are considered. Tortuosity, arterial wall permeability, and porosity have minimal impact on atheroma plaque growth under normal arterial pressure. However, the atheroma plaque growth changes dramatically in hypertensive cases. In such scenarios, the collective influence of all factors—tortuosity, permeability, and porosity—results in nearly a 20% increase in plaque growth. This emphasizes the importance of considering wall compression due to hypertension in patient studies, where elevated blood pressure and high cholesterol levels commonly coexist.

This study aims to examine how changes in material coefficients impact the mechanical responses of AAA models, including both cases with and without the ILT. The main focus will be on identifying the material coefficients that most significantly influence strain and stress fields, using the GHO model, which is widely regarded as the most popular hyperelastic model. The findings of this study reveal that compliant AAAs are particularly sensitive to fiber dispersion, which exerts a substantial influence on stress distribution and deformation patterns. In stiffer AAAs, however, matrix stiffness emerges as the key player. Notably, the study of interactions among all GHO parameters demonstrate that even minor adjustments can dramatically shift model behavior, emphasizing the importance of finely fitted parameter combinations for accurate predictions. The impact of ILT material properties on AAA mechanical behavior was found to be relatively minor, indicating that precise fitting of ILT coefficients may not be essential. However, the inclusion of the ILT itself was important, as it played a crucial role in shielding the AAA wall by reducing stress. This study offers valuable insights into the material modeling of AAA tissue and the significance of the ILT. The findings can be instrumental in optimizing patient-specific computational models, enhancing the accuracy of AAA wall material behavior, while also incorporating the ILT’s effects.

This study aims to provide an in-depth analysis of the mechanical behavior of deep fascia through a comprehensive multidimensional characterization, including uniaxial, biaxial, and planar tension tests. To determine material parameters via test fitting, both a newly developed coupled exponential energy function and a previously proposed uncoupled exponential model—both considering two perpendicular fiber directions—are evaluated. For the uniaxial response, the mean stress measured was 3.96 MPa in the longitudinal direction and 0.6 MPa in the transverse direction at a stretch (λ) of 1.055. In planar tension tests, stress values of 0.43 MPa and 0.11 MPa were recorded for the longitudinal and transverse directions, respectively, at λ = 1.72. Under equibiaxial loading conditions, the mean stresses were 3.16 MPa and 1.2 MPa for the longitudinal and transverse directions when λ reached 1.037, respectively. The fitting results indicate that while the uncoupled exponential model effectively captures the uniaxial and equibiaxial experimental data, it fails to predict other mechanical responses accurately. In contrast, the coupled exponential strain energy function (SEF) demonstrates robust performance in both fitting and prediction. Additionally, an analysis was conducted to assess how the number and combination of tests influence the determination of material parameters. Findings suggest that a single biaxial test incorporating three loading ratios is sufficient to accurately capture and predict uniaxial, planar tension, and other biaxial strain states.

In this study we evaluate the performance of different constitutive biomechanical models, focusing on their ability to reproduce the mechanical behavior of myocardial tissue under various deformation modes. Three constitutive models were analyzed assuming incompressible formulations: the invariant-based formulation of the Costa model, the Holzapfel–Ogden (HO) model, and its extended version (HOE). The study aimed to identify which model provides the best fit for different experimental data, including equibiaxial (EBx), true biaxial (TBx), simple triaxial shear (STS), and combined data sets (Equibiaxial + Shear, True biaxial + Shear). The results showed that the Costa model generally performed better when considering combined datasets, providing a good balance between fitting accuracy and parameter stability, while using the least number of parameters among the contrasted models. The HO model demonstrated reasonable fitting abilities but struggled with non-equibiaxial conditions and clearly orthotropic simple shear datasets. The extended HOE model improved the fitting performance of the standard HO formulation for more complex data, particularly in shear tests, but introduced additional complexity and a higher number of parameters. Therefore, our study highlights the importance of analyzing which validated constitutive formulation is able to adapt to the available experimental data, especially when mixed deformation modes are involved. While all the three models tested performed adequately, the Costa model proved to be the most versatile, especially when dealing with various experimental conditions, providing insights for future research on biomechanical modeling of cardiac tissue.