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

Abstract

Valvular heart diseases are complex disorders, varying in pathophysiological mechanism and affected valve components. Understanding the effects of these diseases on valve functionality requires a thorough characterization of the mechanics and structure of the healthy heart valves. In this study, we performed biaxial mechanical experiments with extensive testing protocols to examine the mechanical behaviors of the mitral valve and tricuspid valve leaflets. We also investigated the effect of loading rate, testing temperatures, species (porcine versus ovine hearts), and age (juvenile vs adult ovine hearts) on the mechanical responses of the leaflet tissues. In addition, we evaluated the structure of chordae tendineae within each valve and performed histological analysis on each atrioventricular leaflet. We found all tissues displayed a characteristic nonlinear anisotropic mechanical response, with radial stretches on average 30.7% higher than circumferential stretches under equibiaxial physiological loading. Tissue mechanical responses showed consistent mechanical stiffening in response to increased loading rate and minor temperature dependence in all five atrioventricular heart valve leaflets. Moreover, our anatomical study revealed similar chordae quantities in the porcine mitral (30.5 ± 1.43 chords) and tricuspid valves (35.3 ± 2.45 chords) but significantly more chordae in the porcine than the ovine valves (p < 0.010). Our histological analyses quantified the relative thicknesses of the four distinct morphological layers in each leaflet. This study provides a comprehensive database of the mechanics and structure of the atrioventricular valves, which will be beneficial to development of subject-specific atrioventricular valve constitutive models and toward multi-scale biomechanical investigations of heart valve function to improve valvular disease treatments.

Mechanics and Microstructure of the Atrioventricular Heart Valve Chordae Tendineae: A Review

“…Interestingly, De Almeida et al noted that fetal hearts had fewer connective tissues (CT) and that there were proportionally fewer "muscular" (thicker, muscular texture) chordae as compared to the adult heart (reflected in both the MV and the TV) [23]. In comparison, we found in our previous study an average of 30 chordae in porcine MV and 35 chordae in the porcine TV, and an average of 15 and 24 chordae in ovine MV and TV, respectively [24]. These differences in the chordae anatomical features should be considered when discussing findings of porcine or ovine chordae studies and their translations to human heart anatomy.…”

Biaxial mechanical data of porcine atrioventricular valve leaflets

“…To avoid the Saint-Venant effects on tissue deformations during our biaxial mechanical testing [2] , four glass beads, served as fiducial markers, were placed in the central delimited region (3 mm × 3 mm) of the valve leaflet specimen ( Fig. 2 c from the companion journal article [1] ). A series of images of the tissue specimen were collected by the high-resolution CCD camera and the time-dependent positions of the four fiducial markers were analyzed based on the acquired images using the DIC-based technique: …”

Structure and Rheological Properties of Bovine Aortic Heart Valve and Pericardium Tissue: Implications in Bioprosthetic and Tissue-Engineered Heart Valves

“…As Paola et al report in his recent study that the bovine and porcine pericardium tissues are most preferable for their availability and traceability. On comparison with porcine pericardial tissue, bovine pericardium tissue is extensively studied due to its optimal mechanical strength for the development of bioprosthetic and TEHV [42]. e complex viscosities of all the samples have decreased with the increase of shear rate, which confirms the shear thinning behavior of the tissues.…”