An Experimental and Computational Investigation to Establish the Mechanical Behaviour of Paediatric Aortic Coarctation Tissue.

Abstract

Purpose: The tissue mechanics resulting in coarctation of the aorta (CoA) remain poorly understood, limiting treatment options, particularly in paediatric patients. Endovascular stenting is the standard of care in adolescents and adults; however current devices are largely used off-label and do not account for the biomechanics or microstructure of the coarcted tissue. This study addresses this knowledge gap by combining uniaxial ring testing, histological assessment and finite element modelling of paediatric aortic coarctation samples to quantify its mechanical behaviour and layer-specific material parameters.

Methods: Aortic coarctation samples were obtained from paediatric patients and analysed using uniaxial ring testing and histology to characterise the tissue's mechanical response and the influence of microstructure. Finite element models were then developed to represent the ductal and aortic layers, and uniaxial ring tests were simulated with material parameters fitted to the experimental data.

Results: Uniaxial ring testing of paediatric aortic coarctation samples revealed marked variability in mechanical behaviour. Histological analysis identified two distinct tissue components-ductal and vessel tissue-with qualitative microstructural differences in collagen and elastin, as well as cellular density and morphology. For the first time, material parameters for the individual tissue components were quantified, with first-order Ogden models shown to best capture the experimental and computational behaviour.

Conclusion: Uniaxial ring testing and histological analysis were used to assess paediatric aortic coarctation samples and to establish fitted material parameters to the experimental data. Quantifying both the combined mechanical response provides preliminary biomechanical data that may be useful for future computational modelling studies investigating aortic coarctation tissue behaviour.