Over length quantification of the multiaxial mechanical properties of the ascending, descending and abdominal aorta using Digital Image Correlation

Abstract

In this paper, we hypothesize that the biaxial mechanical properties of the aorta may be dependent on arterial location. To demonstrate any possible position-related difference, our study analyzed and compared the biaxial mechanical properties of the ascending thoracic aorta, descending thoracic aorta and infrarenal abdominal aorta stemming from the same porcine subjects, and reported values of constitutive parameters for well-known strain energy functions, showing how these mechanical properties are affected by location along the aorta. When comparing ascending thoracic aorta, descending thoracic aorta and infrarenal abdominal aorta, abdominal tissues were found to be stiffer and highly anisotropic. We found that the aorta changed from a more isotropic to a more anisotropic tissue and became progressively less compliant and stiffer with the distance to the heart. We observed substantial differences in the anisotropy parameter between aortic samples where abdominal samples were more anisotropic and nonlinear than the thoracic samples. The phenomenological model was not able to capture the passive biaxial properties of each specific porcine aorta over a wide range of biaxial deformations, showing the best prediction root mean square error ε=0.2621 for ascending thoracic samples and, especially, the worst for the infrarenal abdominal samples ε=0.3780. The micro-structured model with Bingham orientation density function was able to better predict biaxial deformations (ε=0.1372 for ascending thoracic aorta samples). The root mean square error of the micro-structural model and the micro-structured model with von Mises orientation density function were similar for all positions.

Does the Knowledge of the Local Thickness of Human Ascending Thoracic Aneurysm Walls Improve Their Mechanical Analysis?

“…The range of maximum principal stress σ * at a physiological in vivo pressure of 150 mmHg was between 0.12 and 0.25 MPa and that of maximum principal strain E * ranged between 0.12 and 0.95, highlighting a marked local heterogeneity of the mechanical properties. Previous studies already underlined this point with similar experiments on ATAAs (Romo et al, 2014; Davis et al, 2015, 2016; Trabelsi et al, 2015; Duprey et al, 2016) or other biaxial tests on aortic tissue (Bersi et al, 2016; Peña et al, 2018). However, the major limitation of the aforementioned studies was to assume a homogeneous wall thickness, which could alter the calculation of stresses as clearly emphasized from Figure 7.…”

Macro- and Micro-mechanical Properties of the Ovine Aorta: Correlation with Regional Variations in Collagen, Elastin and Glycosaminoglycan Levels

“…In that work, Peña et al [5], found that the aorta was stiffer in the ascending region than the distal region. In the murine aorta, the longitudinal stretch ratio, which is a parameter that describes the ratio of the aorta length during loading and zero-stress, has been found to increase linearly from the ascending aorta to the distal abdominal aorta [11].…”

“…Rupture abdominal aortic aneurysm is a leading cause of death in men over 65 years old [2], a problem exacerbated with the ageing population. It is for this reason that there is substantial interest in the biomechanical behaviour of the aorta [3][4][5]. Biomechanical studies can aid risk evaluation of aortic pathologies and ultimately aid surgical planning and clinical care [4,6].…”

Analysis of the accuracy on computing nominal stress in a biaxial test for arteries

“…These tissues were not randomly chosen. It is well known that the behaviour of the ascending aorta could be considered quasi-isotropic from the point of view of biaxial tests (similar response for circumferential and longitudinal directions) [38]. However, the pulmonary artery has a strongly anisotropic behaviour.…”