Significant differences in the material properties between aged human and porcine aortic tissues

Abstract

Objectives Currently, percutaneous aortic valve (PAV) replacement devices are being investigated to treat aortic stenosis in patients deemed to be of too high a risk for conventional open-chest surgery. Successful PAV deployment and function are heavily reliant on the tissue–stent interaction. Many PAV feasibility trials have been conducted with porcine models under the assumption that these tissues are similar to human; however, this assumption may not be valid. The goal of this study was to characterize and compare the biomechanical properties of aged human and porcine aortic tissues. Methods The biaxial mechanical properties of the left coronary sinus, right coronary sinus, non-coronary sinus, and ascending aorta of eight aged human (90.1 ± 6.8 years) and 10 porcine (6–9 months) hearts were quantified. Tissue structure was analyzed via histological techniques. Results Aged human aortic tissues were significantly stiffer than the corresponding porcine tissues in both the circumferential and longitudinal directions (p < 0.001). In addition, the nearly linear stress–strain behavior of the porcine tissues, compared with the highly nonlinear response of the human tissues at a low strain range, suggested structural differences between the aortic tissues from these two species. Histological analysis revealed that porcine samples were composed of more elastin and less collagen fibers than the respective human samples. Conclusions Significant material and structural differences were observed between the human and porcine tissues, which raise questions on the validity of using porcine models to investigate the biomechanics involved in PAV intervention.

Segmental and age differences in the elastin network, collagen, and smooth muscle phenotype in the tunica media of the porcine aorta

“…However, studies on postnatal ontogenesis of the porcine aorta composition are scarce, although changes in the tunica media composition described in people (e.g. Martin et al, 2011, Tsamis et al, 2013 might alert us to consider these developmental changes.…”

“…Although aged human aortae contain less elastin and more collagen and are therefore stiffer than the corresponding porcine aortic segments (Martin et al, 2011), there are no alternative large laboratory species. The pig aorta is currently the best described and most suitable animal model of the human aorta in terms of its caliber as well as gross and microscopic morphology or physiology.…”

A validated methodology for patient specific computational modeling of self-expandable transcatheter aortic valve implantation

“…The materials were considered to be nearly incompressible, κ was set to 10 MPa as a compromise between incompressibility and simulation stability [Famaey et al, 2012]. The initial value of μ was chosen based on previous experience in modeling cardiovascular tissue, and subsequently optimized to reach a good correspondence between the final simulation result and the stent extracted from the post-operative CT. Table 1 shows the values of the material parameters and the element thickness of the different soft tissues Martin et al, 2011], the density was set to 1000 kg/m 3 . The calcifications were modelled using a linear-elastic material with Young's modulus, E = 5 MPa, Possion's coefficient, ν = 0.475 and density, ρ = 1200 kg/m 3 , comparable values were found in literature [Holzapfel et al, 2004;Morganti et al, 2014].…”

Methodology for Mechanical Characterization of Soft Biological Tissues: Arteries

“…However, they don't converge to a specific methodology to perform the tests [3][4][5][6][7][8][9]. Mathematically, the characterization of the mechanical behavior for soft biological tissue, for example arteries, have been developed within the continuum mechanics framework, and several mathematical models based of Strain Energy Function (SEF) for the material have been proposed [10,11].…”