Mechanical testing of glutaraldehyde cross-linked mitral valves. Part one: In vitro mechanical behaviour

Abstract

The aim of this study was to perform an initial assessment, in vitro, of the feasibility of using a glutaraldehyde cross-linked porcine mitral valve to retain acute functionality, focusing on assessing mitral regurgitation. Six porcine hearts were tested using an in vitro simulator. Testing was repeated following cross-linking of mitral valves; where cross-linking was achieved by placing them in a glutaraldehyde solution. The simulator enabled systolic pressure on the ventricular side of the valve to be mimicked. Following testing, mitral valve leaflets underwent Scanning Electron Microscopy of the ventricular surface of both the anterior and posterior leaflets (1 cm2 samples). The peak pressure withstood by cross-linked valves was significantly lower than for untreated valves (108 mmHg cf. 128 mmHg for untreated valves; p < 0.05). The peak pressure was typically reached 0.5 s later than for the untreated valve. While both cross-linked and untreated valves exhibited endothelium denudation, the unfixed valve had less endothelial loss. Glutaraldehyde cross-linking of porcine mitral valves may be of potential value in assessing improved bioprosthetic mitral valve replacements. However, a more immobile valve exhibiting endothelial denudation (i.e. sclerosis) was a possible concerns identified following in vitro acute assessment.

Mechanical testing of glutaraldehyde cross-linked mitral valves. Part two: Elastic and viscoelastic properties of chordae tendineae

“…cross-linked under tension). 22 Chordae from the former study were used as a measure of chordae cross-linked in the absence of loading; their dynamic viscoelastic properties are available in literature 28 and are hereby referred to as ‘cross-linked unloaded’; that study includes control data. Chordae from this current study, instead, were cross-linked under tension.…”

“…19 Studies into heart valve bioprosthetics have largely been oriented around aortic valve replacements where tissues are treated with glutaraldehyde as a fixative. 20,21 Studies assessing the feasibility of performing mitral valve replacement with a mitral valve bioprosthesis 22 would ideally include the mitral subvalvular apparatus, leading to glutaraldehyde cross-linked chordae.…”

“…19 A recent study of ours on dynamic viscoelasticity found that glutaraldehyde treatment decreased both storage and loss moduli of chordae 28 ; paradoxically, our in vitro observations of glutaraldehyde-treated mitral valves identified limited (not increased) mobility. 22 Although the mechanical properties of natural mitral valve chordae are well documented, 6,29–33 there are inconsistencies in findings from studies of chordae which focus on glutaraldehyde treatment.…”

“…Chordae in tension were cross-linked in situ within an intact mitral valve. 22 Chordae cross-linked in the absence of loading were cross-linked following excision from the mitral valve. Material properties have been evaluated using a uniaxial ramp based elastic characterisation test, 34 and through dynamic mechanical analysis (DMA).…”

“…In this study, data recently published 28 on the viscoelastic properties of basal chordae following glutaraldehyde fixation are compared to the mechanical behaviour of equivalent basal chordae from porcine mitral valves in Part-1 of this study. 22…”