Axial prestretch and circumferential distensibility in biomechanics of abdominal aorta

Abstract

Elastic arteries are significantly prestretched in an axial direction. This property minimises axial deformations during pressure cycle. Ageing-induced changes in arterial biomechanics, among others, are manifested via a marked decrease in the prestretch. Although this fact is well known, little attention has been paid to the effect of decreased prestretch on mechanical response. Our study presents the results of an analytical simulation of the inflation-extension behaviour of the human abdominal aorta treated as nonlinear, anisotropic, prestrained thin-walled as well as thick-walled tube with closed ends. The constitutive parameters and geometries for 17 aortas adopted from the literature were supplemented with initial axial prestretches obtained from the statistics of 365 autopsy measurements. For each aorta, the inflation-extension response was calculated three times, with the expected value of the initial prestretch and with the upper and lower confidence limit of the initial prestretch derived from the statistics. This approach enabled age-related trends to be evaluated bearing in mind the uncertainty in the prestretch. Despite significantly decreased longitudinal prestretch with age, the biomechanical response of human abdominal aorta changes substantially depending on the initial axial stretch was used. In particular, substituting the upper limit of initial prestretch gave mechanical responses which can be characterised by (1) low variation in axial stretch and (2) high circumferential distensibility during pressurisation, in contrast to the responses obtained for their weakly prestretched counterparts. The simulation also suggested the significant effect of the axial prestretch on the variation of axial stress in the pressure cycle. Finally, the obtained results are in accordance with the hypothesis that circumferential-to-axial stiffness ratio is the quantity relatively constant within this cycle.

Constitutive modeling of human saphenous veins at overloading pressures

“…Considering the boundary conditions σ rr (r i )¼ ÀP and σ rr (r o )¼ 0, the equilibrium equations in the radial and axial direction have the form (7) and (8), respectively. Here P denotes internal pressure and F red is the reduced axial (prestretching) force acting on the closed end of the tube additionally to the force generated by the pressure acting on the end (Horný et al, 2014a(Horný et al, , 2014bMatsumoto and Hayashi, 1996).…”

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

“…The data provided in the Supplement 1 can be directly used in biomechanical models of the porcine aorta that are based on histological findings (Sokolis, 2010;Horný et al, 2014aHorný et al, , 2014b. According to the Delesse principle (Howard and Reed, 1998), the area fractions occupied by the components are consistent estimates of the corresponding volume fractions of these components.…”

Segmental differences in the orientation of smooth muscle cells in the tunica media of porcine aortae

“…However, when considering the passive properties of blood vessels only, the contribution of elastin and collagen fibers predominates (Chen et al 2013). Having a relatively low stiffness, elastin fibers support the vascular wall at low pressures, considering also the prestretch of elastin (Cheng et al 2013;Horný et al 2014). Stiff collagen fibers with a nonuniform waviness protect the wall from excessive dilatation (Lanir 1983).…”