A comprehensive experimental analysis of the local passive response across the healthy porcine left ventricle

Laita, Nicolás (Universidad de Zaragoza) ; Aparici-Gil, Alejandro ; Oliván-Viguera, Aida ; Pérez-Martínez, Alba (Universidad de Zaragoza) ; Martínez, Miguel Ángel (Universidad de Zaragoza) ; Doblaré, Manuel (Universidad de Zaragoza) ; Peña, Estefanía (Universidad de Zaragoza)

Resumen: This work provides a comprehensive characterization of porcine myocardial tissue, combining true biaxial (TBx), simple triaxial shear (STS) and confined compression (CC) tests to analyze its elastic behavior under cyclic loads. We expanded this study to different zones of the ventricular free wall, providing insights into the local behavior along the longitudinal and radial coordinates. The aging impact was also assessed by comparing two age groups (4 and 8 months). Resulting data showed that the myocardium exhibits a highly nonlinear hyperelastic and incompressible behavior. We observed an anisotropy ratio of 2-2.4 between averaged peak stresses in TBx tests and 1-0.59-0.40 orthotropy ratios for normalised fiber-sheet-normal peak stresses in STS tests. We obtained a highly incompressible response, reaching volumetric pressures of 2-7 MPa for perfused tissue in CC tests, with notable differences when fluid drainage was allowed, suggesting a high permeability. Regional analysis showed reduced stiffness and anisotropy (20-25%) at the apical region compared to the medial, which we attributed to differences in the fiber field dispersion. Compressibility also increased towards the epicardium and apical regions. Regarding age-related variations, 8-month animals showed stiffer response (at least 25% increase), particularly in directions where the mechanical stress is absorbed by collagenous fibers (more than 90%), as supported by a histological analysis. Although compressibility of perfused tissue remained unchanged, permeability significantly reduced in 8-month-old animals. Our findings offer new insights into myocardial properties, emphasizing on local variations, which can help to get a more realistic understanding of cardiac mechanics in this common animal model. Statement of significance: In this work, we conducted a comprehensive analysis of the passive mechanical behavior of porcine myocardial tissue through biaxial, triaxial shear, and confined compression tests. Unlike previous research, we investigated the variation in mechanical response across the left ventricular free wall, conventionally assumed homogeneous, revealing differences in terms of stiffness and compressibility. Additionally, we evaluated age-related effects on mechanical properties by comparing two age groups, observing significant variations in stiffness and permeability. To date, there has been no such in-depth exploration of myocardial elastic response and compressibility considering regional variations along the wall and may contribute to a better understanding of the cardiac tissue’s passive mechanical response.

Idioma: Inglés

DOI: 10.1016/j.actbio.2024.08.028

Año: 2024

Publicado en: ACTA BIOMATERIALIA 187 (2024), 261-277
ISSN: 1742-7061

Financiación: nfo:eu-repo/grantAgreement/ES/AEI/PID2022-140219OB-I00
Financiación: info:eu-repo/grantAgreement/EC/H2020/874827/EU/Computational biomechanics and bioengineering 3D printing to develop a personalized regenerative biological ventricular assist device to provide lasting functional support to damaged hearts/BRAV3
Financiación: info:eu-repo/grantAgreement/ES/MCIN/PLEC2021-008127
Financiación: info:eu-repo/grantAgreement/ES/UZ/ICTS NANBIOSIS-U13 Unit-CIBER-BBN

Tipo y forma: Article (Published version)

Área (Departamento): Área Teoría Señal y Comunicac. (Dpto. Ingeniería Electrón.Com.)
Área (Departamento): Área Mec.Med.Cont. y Teor.Est. (Dpto. Ingeniería Mecánica)