Investigation into early stage fatigue-damage accumulation in glutaraldehyde-fixed bovine pericardium using a novel equibiaxial bulge inflation system

A primary cause of bioprosthetic heart valve failure is premature degeneration of the pericardial leaflets, owing specifically to mechanical fatigue. There remains a paucity of experimental data and understanding of the fatigue-damage behaviour of this collagenous tissue under complex loading regimes. To meet this knowledge gap, a novel pressure inflation system was designed and built, to cyclically load circular samples of glutaraldehyde fixed bovine pericardium, under equibiaxial bulge conditions. A study up to 60 million cycles revealed new insights into the fatigue behaviour of pericardial tissue, where a statistically significantly higher level of permanent set was found in samples with high collagen fibre dispersion, in comparison to those with highly aligned fibres. Whilst permanent set is known to occur in the non-collagenous matrix of pericardium, this study demonstrates that at physiological loads, which elicit a matrix dominant mechanical response, permanent set and thus tissue-level damage, is still mediated by the underlying collagen fibres.