Biaxial mechanical properties of bovine jugular venous valve leaflet tissues

Abstract

Venous valve incompetence has been implicated in diseases ranging from chronic venous insufficiency (CVI) to intracranial venous hypertension. However, while the mechanical properties of venous valve leaflet tissues are central to CVI biomechanics and mechanobiology, neither stress-strain curves nor tangent moduli have been reported. Here, equibiaxial tensile mechanical tests were conducted to assess the tangent modulus, strength and anisotropy of venous valve leaflet tissues from bovine jugular veins. Valvular tissues were stretched to 60% strain in both the circumferential and radial directions, and leaflet tissue stress-strain curves were generated for proximal and distal valves (i.e., valves closest and furthest from the right heart, respectively). Toward linking mechanical properties to leaflet microstructure and composition, Masson's trichrome and Verhoeff-Van Gieson staining and collagen assays were conducted. Results showed: (1) Proximal bovine jugular vein venous valves tended to be bicuspid (i.e., have two leaflets), while distal valves tended to be tricuspid; (2) leaflet tissues from proximal valves exhibited approximately threefold higher peak tangent moduli in the circumferential direction than in the orthogonal radial direction (i.e., proximal valve leaflet tissues were anisotropic; [Formula: see text]); (3) individual leaflets excised from the same valve apparatus appeared to exhibit different mechanical properties (i.e., intra-valve variability); and (4) leaflets from distal valves exhibited a trend of higher soluble collagen concentrations than proximal ones (i.e., inter-valve variability). To the best of the authors' knowledge, this is the first study reporting biaxial mechanical properties of venous valve leaflet tissues. These results provide a baseline for studying venous valve incompetence at the tissue level and a quantitative basis for prosthetic venous valve design.

An investigation of the anisotropic mechanical properties and anatomical structure of porcine atrioventricular heart valves

“…In order to validate and accurately utilize these computational models in treatment selection, characterization of mechanical and anatomical data of heart valve leaflets is essential [24,25]. In soft tissue biomechanics, planar biaxial mechanical testing employing multiple loading ratios has been utilized to investigate the anisotropic material response of membrane-like connective tissue [26][27][28][29][30][31]. The observed anisotropic and nonlinear material response of many soft tissues, including heart valve leaflets, stems from microstructural collagen and elastin fiber networks with preferred orientations [32][33][34][35].…”

Fluid-structure interaction of blood flow around a vein valve

“…25 Increased pressure applied by gravity as a result of venous valve insufficiency may cause blood accumulation and stasis, edema, inflammation, varicose veins, damage to the lymphatic system and skin, and venous ulcers. 35 The primary mechanism of venous valve incompetency is that the low-shear-stress regions in the pockets behind the leaflets might cause flow stagnation and propagation of venous diseases. 36 The von Mises stress or equivalent tensile stress is a scalar value that is calculated from the Cauchy stress tensor and is corresponding to the distortion energy.…”

“…Increased pressure applied by gravity as a result of venous valve insufficiency may cause blood accumulation and stasis, edema, inflammation, varicose veins, damage to the lymphatic system and skin, and venous ulcers. 35 …”

Effect of valve lesion on venous valve cycle: A modified immersed finite element modeling

“…Recent histological studies [16,42] have indicated that the local nature of the venous valves is transversely isotropic in the longitudinal cross-section. This information helped plausibly assume that the tissues of the valve and wall were pseudoelastic and locally isotropic with respect to the fiber axis [16]. When the constitutive (Eqs 10 and 11) of the hyperelastic model were employed, the fiber-reinforced terms involving α were simplified in the transverse plane.…”

“…They investigated the dynamics of the valve opening area, and captured the unidirectional nature of the blood flow across the venous valve. Owing to a few reports on the mechanical properties [16,17], limited studies have explored venous valve modeling, particularly for the pathological cases [18–22] with insufficient biological knowledge [4]. Of the existing numerical studies, only Soifer et al [19] studied the effects of stiffened venous valves on the neighboring valve using the arbitrary Lagrange–Eulerian (ALE) method.…”