In-vivo heterogeneous functional and residual strains in human aortic valve leaflets

Aggarwal, Ankush; Pouch, Alison M.; Lai, Eric; Lesicko, John; Yushkevich, Paul A.; Gorman, Joseph H.; Gorman, Robert C.; Sacks, Michael S.

doi:10.1016/j.jbiomech.2016.04.038

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In-vivo heterogeneous functional and residual strains in human aortic valve leaflets

Ankush Aggarwal

, Alison M. Pouch, Eric Lai, John Lesicko, Paul A. Yushkevich, Joseph H. Gorman III, Robert C. Gorman, Michael S. Sacks

Journal of Biomechanics, Volume: 49, Issue: 12, Pages: 2481 - 2490

Swansea University Author: Ankush Aggarwal

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DOI (Published version): 10.1016/j.jbiomech.2016.04.038

Abstract

Residual and physiological functional strains in soft tissues are known to play an important role in modulating organ stress distributions. Yet, no known comprehensive information on residual strains exist, or non-invasive techniques to quantify in-vivo deformations for the aortic valve (AV) leaflet...

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Published in:	Journal of Biomechanics
ISSN:	0021-9290
Published:	2016
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URI:	https://cronfa.swan.ac.uk/Record/cronfa27790
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Herein we present a completely non-invasive approach for determining heterogeneous strains – both functional and residual – in semilunar valves and apply it to normal human AV leaflets. Transesophageal 3D echocardiographic (3DE) images of the AV were acquired from open-heart transplant patients, with each AV leaflet excised after heart explant and then imaged in a flattened configuration ex-vivo. Using an established spline parameterization of both 3DE segmentations and digitized ex-vivo images (Aggarwal et al., 2014), surface strains were calculated for deformation between the ex-vivo and three in-vivo configurations: fully open, just-coapted, and fully-loaded. Results indicated that leaflet area increased by an average of 20% from the ex-vivo to in-vivo open states, with a highly heterogeneous strain field. The increase in area from open to just-coapted state was the highest at an average of 25%, while that from just-coapted to fully-loaded remained almost unaltered. Going from the ex-vivo to in-vivo mid-systole configurations, the leaflet area near the basal attachment shrank slightly, whereas the free edge expanded by ~10%. This was accompanied by a 10° −20° shear along the circumferential-radial direction. Moreover, the principal stretches aligned approximately with the circumferential and radial directions for all cases, with the highest stretch being along the radial direction. Collectively, these results indicated that even though the AV did not support any measurable pressure gradient in the just-coapted state, the leaflets were significantly pre-strained with respect to the excised state. Furthermore, the collagen fibers of the leaflet were almost fully recruited in the just-coapted state, making the leaflet very stiff with marginal deformation under full pressure. Lastly, the deformation was always higher in the radial direction and lower along the circumferential one, the latter direction made stiffer by the preferential alignment of collagen fibers. 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spelling	2020-07-20T11:44:21.4219795 v2 27790 2016-05-10 In-vivo heterogeneous functional and residual strains in human aortic valve leaflets 33985d0c2586398180c197dc170d7d19 0000-0002-1755-8807 Ankush Aggarwal Ankush Aggarwal true false 2016-05-10 EEN Residual and physiological functional strains in soft tissues are known to play an important role in modulating organ stress distributions. Yet, no known comprehensive information on residual strains exist, or non-invasive techniques to quantify in-vivo deformations for the aortic valve (AV) leaflets. Herein we present a completely non-invasive approach for determining heterogeneous strains – both functional and residual – in semilunar valves and apply it to normal human AV leaflets. Transesophageal 3D echocardiographic (3DE) images of the AV were acquired from open-heart transplant patients, with each AV leaflet excised after heart explant and then imaged in a flattened configuration ex-vivo. Using an established spline parameterization of both 3DE segmentations and digitized ex-vivo images (Aggarwal et al., 2014), surface strains were calculated for deformation between the ex-vivo and three in-vivo configurations: fully open, just-coapted, and fully-loaded. Results indicated that leaflet area increased by an average of 20% from the ex-vivo to in-vivo open states, with a highly heterogeneous strain field. The increase in area from open to just-coapted state was the highest at an average of 25%, while that from just-coapted to fully-loaded remained almost unaltered. Going from the ex-vivo to in-vivo mid-systole configurations, the leaflet area near the basal attachment shrank slightly, whereas the free edge expanded by ~10%. This was accompanied by a 10° −20° shear along the circumferential-radial direction. Moreover, the principal stretches aligned approximately with the circumferential and radial directions for all cases, with the highest stretch being along the radial direction. Collectively, these results indicated that even though the AV did not support any measurable pressure gradient in the just-coapted state, the leaflets were significantly pre-strained with respect to the excised state. Furthermore, the collagen fibers of the leaflet were almost fully recruited in the just-coapted state, making the leaflet very stiff with marginal deformation under full pressure. Lastly, the deformation was always higher in the radial direction and lower along the circumferential one, the latter direction made stiffer by the preferential alignment of collagen fibers. These results provide significant insight into the distribution of residual strains and the in-vivo strains encountered during valve opening and closing in AV leaflets, and will form an important component of the tool that can evaluate valve׳s functional properties in a non-invasive manner. Journal Article Journal of Biomechanics 49 12 2481 2490 0021-9290 Heart valves; Aortic valve; Valve mechanics; Residual strains; In-vivo analysis 16 8 2016 2016-08-16 10.1016/j.jbiomech.2016.04.038 COLLEGE NANME Engineering COLLEGE CODE EEN Swansea University 2020-07-20T11:44:21.4219795 2016-05-10T13:34:00.5620353 Faculty of Science and Engineering School of Engineering and Applied Sciences - Uncategorised Ankush Aggarwal 0000-0002-1755-8807 1 Alison M. Pouch 2 Eric Lai 3 John Lesicko 4 Paul A. Yushkevich 5 Joseph H. Gorman III 6 Robert C. Gorman 7 Michael S. Sacks 8 0027790-10052016133503.pdf JB-pre-strain-AV-revised.pdf 2016-05-10T13:35:03.6970000 Output 1529768 application/pdf Accepted Manuscript true 2017-05-06T00:00:00.0000000 true
title	In-vivo heterogeneous functional and residual strains in human aortic valve leaflets
spellingShingle	In-vivo heterogeneous functional and residual strains in human aortic valve leaflets Ankush Aggarwal
title_short	In-vivo heterogeneous functional and residual strains in human aortic valve leaflets
title_full	In-vivo heterogeneous functional and residual strains in human aortic valve leaflets
title_fullStr	In-vivo heterogeneous functional and residual strains in human aortic valve leaflets
title_full_unstemmed	In-vivo heterogeneous functional and residual strains in human aortic valve leaflets
title_sort	In-vivo heterogeneous functional and residual strains in human aortic valve leaflets
author_id_str_mv	33985d0c2586398180c197dc170d7d19
author_id_fullname_str_mv	33985d0c2586398180c197dc170d7d19_***_Ankush Aggarwal
author	Ankush Aggarwal
author2	Ankush Aggarwal Alison M. Pouch Eric Lai John Lesicko Paul A. Yushkevich Joseph H. Gorman III Robert C. Gorman Michael S. Sacks
format	Journal article
container_title	Journal of Biomechanics
container_volume	49
container_issue	12
container_start_page	2481
publishDate	2016
institution	Swansea University
issn	0021-9290
doi_str_mv	10.1016/j.jbiomech.2016.04.038
college_str	Faculty of Science and Engineering
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hierarchy_top_id	facultyofscienceandengineering
hierarchy_top_title	Faculty of Science and Engineering
hierarchy_parent_id	facultyofscienceandengineering
hierarchy_parent_title	Faculty of Science and Engineering
department_str	School of Engineering and Applied Sciences - Uncategorised{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Engineering and Applied Sciences - Uncategorised
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description	Residual and physiological functional strains in soft tissues are known to play an important role in modulating organ stress distributions. Yet, no known comprehensive information on residual strains exist, or non-invasive techniques to quantify in-vivo deformations for the aortic valve (AV) leaflets. Herein we present a completely non-invasive approach for determining heterogeneous strains – both functional and residual – in semilunar valves and apply it to normal human AV leaflets. Transesophageal 3D echocardiographic (3DE) images of the AV were acquired from open-heart transplant patients, with each AV leaflet excised after heart explant and then imaged in a flattened configuration ex-vivo. Using an established spline parameterization of both 3DE segmentations and digitized ex-vivo images (Aggarwal et al., 2014), surface strains were calculated for deformation between the ex-vivo and three in-vivo configurations: fully open, just-coapted, and fully-loaded. Results indicated that leaflet area increased by an average of 20% from the ex-vivo to in-vivo open states, with a highly heterogeneous strain field. The increase in area from open to just-coapted state was the highest at an average of 25%, while that from just-coapted to fully-loaded remained almost unaltered. Going from the ex-vivo to in-vivo mid-systole configurations, the leaflet area near the basal attachment shrank slightly, whereas the free edge expanded by ~10%. This was accompanied by a 10° −20° shear along the circumferential-radial direction. Moreover, the principal stretches aligned approximately with the circumferential and radial directions for all cases, with the highest stretch being along the radial direction. Collectively, these results indicated that even though the AV did not support any measurable pressure gradient in the just-coapted state, the leaflets were significantly pre-strained with respect to the excised state. Furthermore, the collagen fibers of the leaflet were almost fully recruited in the just-coapted state, making the leaflet very stiff with marginal deformation under full pressure. Lastly, the deformation was always higher in the radial direction and lower along the circumferential one, the latter direction made stiffer by the preferential alignment of collagen fibers. These results provide significant insight into the distribution of residual strains and the in-vivo strains encountered during valve opening and closing in AV leaflets, and will form an important component of the tool that can evaluate valve׳s functional properties in a non-invasive manner.
published_date	2016-08-16T03:33:46Z
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score	11.013148

In-vivo heterogeneous functional and residual strains in human aortic valve leaflets

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