Frequency and diameter dependent viscoelastic properties of mitral valve chordae tendineae

Abstract

This study aimed to characterise viscoelastic properties of different categories of chordae tendineae over a range of frequencies. Dynamic Mechanical Analysis (DMA) was performed using a materials testing machine. Chordae (n=51) were dissected from seven porcine hearts and categorised as basal, marginal, strut or commissural. Chordae were loaded under a sinusoidally varying tensile load at a range of frequencies between 0.5 and 5Hz, both at a standardised load (i.e. same mean load of 4N for all chordae) and under chordal specific loading (i.e. based on in vivo loads for different chordae). Storage modulus and stiffness were frequency-dependent. Loss modulus and stiffness were frequency-independent. Storage and loss moduli, but not stiffness, decreased with chordal diameter. Therefore, strut chordae have the lowest moduli and marginal chordae the highest moduli. The hierarchy of dynamic storage and loss moduli is: marginal, commissural, basal and strut. In conclusion, viscoelastic properties of chordae are dependent on both frequency and chordal type. Future/novel replacement chordal materials should account for frequency and diameter dependent viscoelastic properties of chordae tendineae.

Viscoelastic properties of human periodontal ligament: Effects of the loading frequency and location

“…16 In terms of simulating occlusal load under physiological or traumatic conditions, the present study used DMA to interpret the dynamic tensile properties of the human PDL in a frequency range of 0.1 and 10 Hz. The results of the present study were consistent with those reported before, 10,11 in which the measured storage and loss moduli increased as a function of frequency, but tand showed small variation with the frequency. In comparison to the dynamic shear properties of porcine PDL, 17 the dynamic modulus in the present study was higher at comparable frequencies.…”

“…Since the 1990s, dynamic mechanical analysis (DMA) has been used to investigate the viscoelastic properties of biological tissue, such as lens, 8 articular cartilage, 9 cardiovascular tissue, 10 bladder tissue, 11 and so on. The frequency dependency of the storage (E 0 ) and loss (E 00 ) moduli of various biomaterials was obtained from DMA testing.…”

Towards viscoelastic characterisation of the human ulnar nerve: An early assessment using embalmed cadavers

“…While much of this range of frequencies may not appear physiological, characterisation of natural tissues should consider not only physiological rates of loading, but also loading associated with exercise, other daily activities, pathophysiology and/or trauma [23,24,35]. However, loading rates and equivalent frequencies associated with loading of the upper-limb/elbow, and of potential relevance to the ulnar nerve are less well understood than, say, for natural tissues such as for heart valves [35][36][37] or lower limbs [23,38,39]. However, there are upper-limb studies which suggest that frequencies of 20 repeats/min (0.33 Hz) are associated with discomfort levels within a physiological loading range [40], providing a lower range for an experimental loading frequency.…”

Modelling mitral valvular dynamics–current trend and future directions

“…68 It is challenging to model the mechanical behaviour of the MV accounting for all the anisotropic and nonlinear behaviour; the coupling between different directions, the differences of in vivo and ex vivo, and the residual strain and strain-path dependence. The MV material properties are mainly derived from animal heart valvular experiments 17,[69][70][71][72][73][74][75][76] . In uniaxial studies of excised leaflets, Kunzelman and Cochran 17 measured the stress-strain behaviour of MV within distinct pretransitional and posttransitional regions.…”