Correlation of structure and viscoelastic properties in the pericardia of four mammalian species

Abstract

Although the pericardium is recognized as having important contributions to ventricular function, the relationship between its functional role and structural composition remains poorly understood. Conflicting evidence from low strain rate experiments has shown that differences exist between the mechanical properties of canine, human, and bovine pericardium but with no structural explanation for these differences. This paper examines the pericardia of calves, dogs, pigs, and sheep using a structural/mechanical approach with techniques novel to the pericardial literature. High strain rate mechanical testing for stress-strain response, stress relaxation, and forced vibration response has shown the pericardium to be much more viscoelastic than previously believed under large deformations, but to be quite elastic in small vibrations. The thinner canine and porcine pericardia were found to be significantly stiffer than the thicker bovine and ovine tissues, but equivalently viscoelastic. Biochemical analysis shows these thinner tissues to have significantly higher levels of type III collagen combined with a higher degree of cross-linking. This is the first structural explanation for differences in mechanical properties between the pericardia of different species.

HMDC crosslinking of bovine pericardial tissue: a potential role of the solvent environment in the design of bioprosthetic materials

“…By contrast, the increased strain at fracture for the HMDC group may be explained by increased collagen crimp after crosslinking which subsequently collapses under high stress levels [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. This observation is consistent with the dimensional shrinkage seen in glutaraldehyde crosslinking by Trowbridge and co-workers and calculated by Lee et al [31,18].…”

“…Initially, there is a decrease in load due to stress relaxation. Eventually, the temperature of the bath provides enough energy to break hydrogen bonds which stabilize the highly ordered helical structure of this predominantly collagenous material [18]. This results in a conformational change into a random coil configuration which would produce observable shrinkage of the tissue were it unconstrained; however, since the tissue is held at a fixed extension (isometric constraint), the point at which the tissue denatures is registered as a sharp increase in the force exerted on the tissue strip.…”

Time-dependent biaxial mechanical behavior of the aortic heart valve leaflet

“…Similarly, Naimark et al (Naimark et al, 1992) showed no significant strain rate dependence in the stress-strain relationship of mammalian pericardia for strain rates between 1 and 100%/s. The authors speculated strain rate insensitivity may be attributed to the stabilizing effects of glycosaminoglycans that surround the pericardial collagen fibers.…”

Hydration of glutaraldehyde‐fixed pericardium tissue: Raman spectroscopic study

“…The contribution of collagen type I can be estimated as 71.8 š 2.1% (dry weight). 21 Three 15 ð 10 mm rectangles were excised from each pericardium.…”