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Salmasi MY, Sasidharan S, Frattolin J, Edgar L, Stock U, Athanasiou T, Moore Jr J. Regional variation in biomechanical properties of ascending thoracic aortic aneurysms. Eur J Cardiothorac Surg 2022; 62:6650693. [PMID: 35894942 PMCID: PMC9731372 DOI: 10.1093/ejcts/ezac392] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 06/30/2022] [Accepted: 07/22/2022] [Indexed: 12/15/2022] Open
Abstract
OBJECTIVES This study aims to characterize the material properties of ascending thoracic aortic aneurysmal tissue, using regional biomechanical assessment of both tensile and dissection propagation peel strength. METHODS Thirty-four aneurysm specimens (proximal thoracic aorta) were harvested en-bloc from patients undergoing surgery for aneurysm replacement. Specimens were processed into regional samples of similar shapes covering the whole aneurysm isosurface, according to a structured protocol, in both orientations (longitudinal and circumferential). Thickness mapping, uniaxial tensile and peel tests were conducted, enabling calculation of the following parameters: true stress/strain, tangential modulus, tensile strength, peeling force and dissection energy. Two constitutive material models were used (hyperelastic models of Delfino and Ogden) to fit the data. A circumferential strip of tissue was also obtained for computational histology [regional quantification of (i) elastin, (ii) collagen and (iii) smooth muscle cells]. RESULTS The aortic wall was thinner on the outer curve (2.21, standard deviation (SD) 0.4 mm vs inner curve 2.50, SD 0.12 mm). Advanced patient age and higher pulse wave velocity (externally measured) were predictors of increased aortic wall thickness. Tensile strength was higher in the circumferential versus longitudinal direction when analysed according to anatomical regions. Both peel force (35.5, 22 N/m) and dissection energy (88.5, 69 J/m2) were on average lowest at the outer curve of the aneurysm in the longitudinal orientation. Delfino and Ogden model constants varied throughout anatomical regions, with the outer curve being associated a higher ɑ constant (Delfino) and lower µ1 constant (Ogden) (P < 0.05) indicating increased stiffness. Histologically, collagen abundance was significantly related to circumferential and longitudinal strength (P= 0.010), whilst smooth muscle cell count had no relation with any mechanical property (P > 0.05). CONCLUSIONS Our results suggest that the outer aortic curve is more prone to dissection propagation and perhaps less prone to rupture than the inner aortic curve. This strengthens the notion of disease heterogeneity in ascending thoracic aortic aneurysms and has implications for the pathogenesis of aortic dissection.
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Affiliation(s)
- M Yousuf Salmasi
- Corresponding author. Imperial College London, 10th Floor, QEQM Building, St Mary’s Campus, South Wharf Road, London W2 1NY, UK. e-mail: (M.Y. Salmasi)
| | | | - Jennifer Frattolin
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London, UK
| | - Lowell Edgar
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London, UK
| | - Ulrich Stock
- Department of Cardiac Surgery and Transplantation, Royal Brompton and Harefield Foundation Trust, London, UK
| | - Thanos Athanasiou
- Department of Surgery and Cancer, Imperial College London, London, UK
| | - James Moore Jr
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London, UK
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Salmasi MY, Pirola S, Sasidharan S, Fisichella SM, Redaelli A, Jarral OA, O'Regan DP, Oo AY, Moore JE, Xu XY, Athanasiou T. High Wall Shear Stress can Predict Wall Degradation in Ascending Aortic Aneurysms: An Integrated Biomechanics Study. Front Bioeng Biotechnol 2021; 9:750656. [PMID: 34733832 PMCID: PMC8558434 DOI: 10.3389/fbioe.2021.750656] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 09/24/2021] [Indexed: 01/16/2023] Open
Abstract
Background: Blood flow patterns can alter material properties of ascending thoracic aortic aneurysms (ATAA) via vascular wall remodeling. This study examines the relationship between wall shear stress (WSS) obtained from image-based computational modelling with tissue-derived mechanical and microstructural properties of the ATAA wall using segmental analysis. Methods: Ten patients undergoing surgery for ATAA were recruited. Exclusions: bicuspid aortopathy, connective tissue disease. All patients had pre-operative 4-dimensional flow magnetic resonance imaging (4D-MRI), allowing for patient-specific computational fluid dynamics (CFD) analysis and anatomically precise WSS mapping of ATAA regions (6-12 segments per patient). ATAA samples were obtained from surgery and subjected to region-specific tensile and peel testing (matched to WSS segments). Computational pathology was used to characterize elastin/collagen abundance and smooth muscle cell (SMC) count. Results: Elevated values of WSS were predictive of: reduced wall thickness [coef -0.0489, 95% CI (-0.0905, -0.00727), p = 0.022] and dissection energy function (longitudinal) [-15,0, 95% CI (-33.00, -2.98), p = 0.048]. High WSS values also predicted higher ultimate tensile strength [coef 0.136, 95% CI (0 0.001, 0.270), p = 0.048]. Additionally, elevated WSS also predicted a reduction in elastin levels [coef -0.276, 95% (CI -0.531, -0.020), p = 0.035] and lower SMC count ([oef -6.19, 95% CI (-11.41, -0.98), p = 0.021]. WSS was found to have no effect on collagen abundance or circumferential mechanical properties. Conclusions: Our study suggests an association between elevated WSS values and aortic wall degradation in ATAA disease. Further studies might help identify threshold values to predict acute aortic events.
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Affiliation(s)
- M Yousuf Salmasi
- Department of Surgery and Cancer, Imperial College London, London, United Kingdom
| | - Selene Pirola
- Department of Chemical Engineering, Imperial College London, London, United Kingdom
| | - Sumesh Sasidharan
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Serena M Fisichella
- Department of Chemical Engineering, Imperial College London, London, United Kingdom.,Politecnico di Milano, Milan, Italy
| | | | - Omar A Jarral
- Department of Surgery and Cancer, Imperial College London, London, United Kingdom
| | - Declan P O'Regan
- MRC London Institute of Medical Sciences, Imperial College London, London, United Kingdom
| | - Aung Ye Oo
- Barts Heart Centre, London, United Kingdom
| | - James E Moore
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Xiao Yun Xu
- Department of Chemical Engineering, Imperial College London, London, United Kingdom
| | - Thanos Athanasiou
- Department of Surgery and Cancer, Imperial College London, London, United Kingdom
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Campobasso R, Condemi F, Viallon M, Croisille P, Campisi S, Avril S. Evaluation of Peak Wall Stress in an Ascending Thoracic Aortic Aneurysm Using FSI Simulations: Effects of Aortic Stiffness and Peripheral Resistance. Cardiovasc Eng Technol 2018; 9:707-722. [DOI: 10.1007/s13239-018-00385-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2018] [Accepted: 10/08/2018] [Indexed: 12/25/2022]
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Niestrawska JA, Ch Haspinger D, Holzapfel GA. The influence of fiber dispersion on the mechanical response of aortic tissues in health and disease: a computational study. Comput Methods Biomech Biomed Engin 2018; 21:99-112. [PMID: 29436874 DOI: 10.1080/10255842.2017.1418862] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Changes in the structural components of aortic tissues have been shown to play a significant role in the pathogenesis of aortic degeneration. Therefore, reliable stress analyses require a suitable and meaningful constitutive model that captures micro-structural changes. As recent data show, in-plane and out-of-plane collagen fiber dispersions vary significantly between healthy and aneurysmatic aortic walls. The aim of this study is to computationally investigate the influence of fiber dispersion on the mechanical response of aortic tissues in health and disease. In particular, the influence of three different fiber dispersions is studied: (i) non-rotationally symmetric dispersion, the most realistic assumption for aortic tissues; (ii) transversely isotropic dispersion, a special case; (iii) perfectly aligned fibers (no dispersion in either plane), another special case. Explicit expressions for the stress and elasticity tensors as needed for the implementation in a finite element code are provided. Three representative numerical examples are studied: planar biaxial extension, inflation of residually stressed and pre-stretched aortic segments and inflation of an idealized abdominal aortic aneurysm (AAA) geometry. For the AAA geometry the case of isotropic dispersion is additionally analyzed. Documented structural and mechanical parameters are taken from human aortas (healthy media/adventitia and AAA). The influence of fiber dispersions upon magnitudes and distributions of stresses and deformations are presented and analyzed. Stresses vary significantly, especially in the AAA case, where material stiffening is significantly influenced by fiber dispersion. The results highlight the need to incorporate the structural differences into finite element simulations to obtain more accurate stress predictions. Additionally, results show the capability of one constitutive model to represent different scenarios of aortic micro-structures allowing future studies of collagen reorientation during disease progression.
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Affiliation(s)
| | - Daniel Ch Haspinger
- a Institute of Biomechanics , Graz University of Technology , Graz , Austria
| | - Gerhard A Holzapfel
- a Institute of Biomechanics , Graz University of Technology , Graz , Austria .,b Faculty of Engineering Science and Technology , Norwegian University of Science and Technology (NTNU) , Trondheim , Norway
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Modelling and numerical simulation of the in vivo mechanical response of the ascending aortic aneurysm in Marfan syndrome. Med Biol Eng Comput 2016; 55:419-428. [DOI: 10.1007/s11517-016-1524-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Accepted: 05/11/2016] [Indexed: 12/25/2022]
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Blose KJ, Ennis TL, Arif B, Weinbaum JS, Curci JA, Vorp DA. Periadventitial adipose-derived stem cell treatment halts elastase-induced abdominal aortic aneurysm progression. Regen Med 2015; 9:733-41. [PMID: 25431910 DOI: 10.2217/rme.14.61] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
AIM Demonstrate that periadventitial delivery of adipose-derived mesenchymal stem cells (ADMSCs) slows aneurysm progression in an established murine elastase-perfusion model of abdominal aortic aneurysm (AAA). MATERIALS & METHODS AAAs were induced in C57BL/6 mice using porcine elastase. During elastase perfusion, a delivery device consisting of a subcutaneous port, tubing and porous scaffold was implanted. Five days after elastase perfusion, 100,000 ADMSCs were delivered through the port to the aorta. After sacrifice at day 14, analyzed metrics included aortic diameter and structure of aortic elastin. RESULTS ADMSC treated aneurysms had a smaller diameter and less fragmented elastin versus saline controls. CONCLUSION Periadventitial stem cell delivery prevented the expansion of an established aneurysm between days 5 and 14 after elastase perfusion.
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Affiliation(s)
- Kory J Blose
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
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Avanzini A, Battini D, Bagozzi L, Bisleri G. Biomechanical evaluation of ascending aortic aneurysms. BIOMED RESEARCH INTERNATIONAL 2014; 2014:820385. [PMID: 24991568 PMCID: PMC4065659 DOI: 10.1155/2014/820385] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 04/21/2014] [Indexed: 11/27/2022]
Abstract
The biomechanical properties of ascending aortic aneurysms were investigated only in the last decade in a limited number of studies. Indeed, in recent years, there has been a growing interest in this field in order to identify new predictive parameters of risk of dissection, which may have clinical relevance. The researches performed so far have been conducted according to the methods used in the study of abdominal aortic aneurysms. In most cases, uniaxial or biaxial tensile tests were used, while in a smaller number of studies other methods, such as opening angle, bulge inflation, and inflation-extension tests, were used. However, parameters and protocols of these tests are at present very heterogeneous in the studies reported in the literature, and, therefore, the results are not comparable and are sometimes conflicting. The purpose of this review then thence to provide a comprehensive analysis of the experimental methodology for determination of biomechanical properties in the specific field of aneurysms of the ascending aorta to allow for better comparison and understanding of the results.
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Affiliation(s)
- Andrea Avanzini
- Department of Industrial and Mechanical Engineering, University of Brescia, Via Branze 38, 25123 Brescia, Italy
| | - Davide Battini
- Department of Industrial and Mechanical Engineering, University of Brescia, Via Branze 38, 25123 Brescia, Italy
| | - Lorenzo Bagozzi
- Division of Cardiac Surgery, University of Brescia, P.le Spedali Civili 1, 25123 Brescia, Italy
| | - Gianluigi Bisleri
- Division of Cardiac Surgery, University of Brescia, P.le Spedali Civili 1, 25123 Brescia, Italy
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Effect of layer heterogeneity on the biomechanical properties of ascending thoracic aortic aneurysms. Med Biol Eng Comput 2012; 50:1227-37. [DOI: 10.1007/s11517-012-0949-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Accepted: 08/08/2012] [Indexed: 11/25/2022]
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