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Asgari M, Latifi N, Giovanniello F, Espinosa HD, Amabili M. Revealing Layer‐Specific Ultrastructure and Nanomechanics of Fibrillar Collagen in Human Aorta via Atomic Force Microscopy Testing: Implications on Tissue Mechanics at Macroscopic Scale. ADVANCED NANOBIOMED RESEARCH 2022. [DOI: 10.1002/anbr.202100159] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- Meisam Asgari
- Department of Mechanical Engineering McGill University 817 Sherbrooke Street West Montreal QC H3A 0C3 Canada
- Theoretical and Applied Mechanics Program Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Neda Latifi
- Department of Mechanical and Industrial Engineering University of Toronto 5 King's College Road Toronto ON M5S 3G8 Canada
| | - Francesco Giovanniello
- Department of Mechanical Engineering McGill University 817 Sherbrooke Street West Montreal QC H3A 0C3 Canada
| | - Horacio D. Espinosa
- Theoretical and Applied Mechanics Program Northwestern University 2145 Sheridan Road Evanston IL 60208 USA
| | - Marco Amabili
- Department of Mechanical Engineering McGill University 817 Sherbrooke Street West Montreal QC H3A 0C3 Canada
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Jeon KH, Kim HL, Lim WH, Seo JB, Kim SH, Zo JH, Kim MA. Associations between measurements of central blood pressure and target organ damage in high-risk patients. Clin Hypertens 2021; 27:23. [PMID: 34847966 PMCID: PMC8638411 DOI: 10.1186/s40885-021-00179-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 09/09/2021] [Indexed: 11/17/2022] Open
Abstract
Background It is not well-known which components of central blood pressure (CBP) are more influential to target organ damage (TOD). This study aimed to determine the relationship between CBP measurements and various types of TOD in high-risk patients. Methods A total of 148 patients who had documented atherosclerotic cardiovascular disease or its multiple risk factors were prospectively enrolled. CBP was measured by using applanation tonometry of the radial artery. The following nine TOD parameters were evaluated: left ventricular mass index, relative wall thickness, septal e′ velocity, septal E/e′, brachial-ankle pulse wave velocity, ankle-brachial index, estimated glomerular filtration rate, urine protein and obstructive coronary artery disease. Results The mean age of the study population was 67.1 ± 9.0 years and 108 (73 %) were male. Among four CBP measurements (systolic, diastolic, mean, and pulse pressures), central pulse pressure (CPP) was associated with the largest number of TOD parameters. As CPP increased, the number of TOD increased (P = 0.010), but this association was not observed in other CBP measurements (P > 0.05 for each). Conclusions CPP had a stronger correlation with TOD than other CBP measurements. Non-invasive CPP could be a useful indicator for predicting TOD in patients at high coronary risk.
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Affiliation(s)
- Ki-Hyun Jeon
- Cardiovascular center, Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
| | - Hack-Lyoung Kim
- Division of Cardiology, Department of Internal Medicine, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea.
| | - Woo-Hyun Lim
- Division of Cardiology, Department of Internal Medicine, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea
| | - Jae-Bin Seo
- Division of Cardiology, Department of Internal Medicine, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea
| | - Sang-Hyun Kim
- Division of Cardiology, Department of Internal Medicine, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea
| | - Joo-Hee Zo
- Division of Cardiology, Department of Internal Medicine, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea
| | - Myung-A Kim
- Division of Cardiology, Department of Internal Medicine, SMG-SNU Boramae Medical Center, Seoul, Republic of Korea
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Raayai-Ardakani S, Chen Z, Earl DR, Cohen T. Volume-controlled cavity expansion for probing of local elastic properties in soft materials. SOFT MATTER 2019; 15:381-392. [PMID: 30534776 DOI: 10.1039/c8sm02142b] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Cavity expansion can be used to measure the local nonlinear elastic properties in soft materials, regardless of the specific damage or instability mechanism that it may ultimately induce. To that end, we introduce a volume-controlled cavity expansion procedure and an accompanying method that builds on the Cavitation Rheology technique [J. A. Zimberlin et al., Soft Matter, 2007, 3, 763-767], but without relying on the maximum recorded pressure. This is achieved by determining an effective radius of the cavity that is based on the volume measurements, and is further supported by numerical simulations. Applying this method to PDMS samples, we show that it consistently collapses the experimental curves to the theoretical prediction of cavity expansion prior to the occurrence of fracture or cavitation, thus resulting in high precision measurement with less than 5% of scatter and good agreement with results obtained via conventional techniques. Moreover, since it does not require visual tracking of the cavity, this technique can be applied to measure the nonlinear elastic response in opaque samples.
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Affiliation(s)
- Shabnam Raayai-Ardakani
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA.
| | - Zhantao Chen
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA
| | - Darla Rachelle Earl
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA.
| | - Tal Cohen
- Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA. and Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, USA
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Yaguchi T, Cong Y, Shimo K, Kurokawa T, Sugita S, Nagayama K, Masuda H, Matsumoto T. A Novel Apparatus for the Multifaceted Evaluation of Arterial Function Through Transmural Pressure Manipulation. Ann Biomed Eng 2017; 45:1487-1495. [PMID: 28194660 DOI: 10.1007/s10439-017-1810-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2016] [Accepted: 02/04/2017] [Indexed: 11/28/2022]
Abstract
A novel apparatus for the multifaceted evaluation of artery function was developed. It measures endothelial and smooth muscle functions and the pressure-strain elastic modulus (E p). A rigid airtight chamber with an ultrasound probe was attached to the upper arm to manipulate the transmural pressure of the brachial artery. Endothelial function was measured via a standard flow-mediated dilation (FMD) protocol. Smooth muscle function was evaluated via a myogenic contraction of the artery following the application of negative pressure to the chamber and was named pressure-mediated contraction (PMC). E p was obtained by measuring the instantaneous increase in the artery diameter following the negative pressure application. The PMC and FMD values had a significant negative correlation with age, indicating that the age-related decrease in FMD is caused by the decay of endothelial and smooth muscle function. A consideration of PMC may help improve the accuracy of artery function measurement. E p in subjects aged >40 years was found to be significantly higher in the supra-physiological pressure range than in the physiological one (p = 0.02); this did not occur in younger subjects. Artery stiffening may begin in the supra-physiological range, and this stiffness may also be used for the diagnosis of atherosclerosis.
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Affiliation(s)
- Toshiyuki Yaguchi
- Biomechanics Laboratory, Department of Mechanical Engineering, Nagoya Institute of Technology, Nagoya, 466-8555, Japan. .,Division of Electronic and Mechanical Engineering, Department of Science and Engineering, School of Science and Engineering, Tokyo Denki University, Hikigun, 350-0394, Japan.
| | - Yalin Cong
- Biomechanics Laboratory, Department of Mechanical Engineering, Nagoya Institute of Technology, Nagoya, 466-8555, Japan
| | - Kenji Shimo
- Biomechanics Laboratory, Department of Mechanical Engineering, Nagoya Institute of Technology, Nagoya, 466-8555, Japan
| | - Takahiro Kurokawa
- Biomechanics Laboratory, Department of Mechanical Engineering, Nagoya Institute of Technology, Nagoya, 466-8555, Japan
| | - Shukei Sugita
- Biomechanics Laboratory, Department of Mechanical Engineering, Nagoya Institute of Technology, Nagoya, 466-8555, Japan
| | - Kazuaki Nagayama
- Biomechanics Laboratory, Department of Mechanical Engineering, Nagoya Institute of Technology, Nagoya, 466-8555, Japan.,Department of Intelligent Systems Engineering, College of Engineering, Ibaraki University, Hitachi, 316-8511, Japan
| | | | - Takeo Matsumoto
- Biomechanics Laboratory, Department of Mechanical Engineering, Nagoya Institute of Technology, Nagoya, 466-8555, Japan. .,Biomechanics Laboratory, Department of Mechanical Science and Engineering, Graduate School of Engineering, Nagoya University, Nagoya, 464-8603, Japan.
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Hayashi K, Hirayama E. Age-related changes of wall composition and collagen cross-linking in the rat carotid artery – In relation with arterial mechanics. J Mech Behav Biomed Mater 2017; 65:881-889. [DOI: 10.1016/j.jmbbm.2016.10.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Revised: 10/12/2016] [Accepted: 10/17/2016] [Indexed: 01/20/2023]
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Hayashi K, Higaki M. Stiffness of Intact Endothelial Cells From Fresh Aortic Bifurcations of Atherosclerotic Rabbits-Atomic Force Microscopic Study. J Cell Physiol 2016; 232:7-13. [PMID: 26991605 DOI: 10.1002/jcp.25379] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 03/14/2016] [Indexed: 12/16/2022]
Abstract
Stiffness of intact endothelial cells (ECs) in the abdominal aorta (AA) and in the medial and lateral wall of the common iliac artery (CIA(Medial) and CIA(Lateral), respectively), which were freshly obtained from cholesterol-fed rabbits, were measured with an atomic force microscopic indentation method. In the areas away from atherosclerotic plaques (Off-plaque), ECs were significantly stiffer in CIA(Medial) than in the other two locations; this result was similar to that from normal diet-fed animals. On the other hand, there were no significant differences in the stiffness of ECs located on atherosclerotic plaques (On-plaque) among the three sites; the stiffness was equal to those in "Off-plaque" wall of CIA(Lateral) and AA. Moreover, the stiffness of ECs covering plaques decreased with the progression of atherosclerosis. The precise quantification of the stiffness of vascular ECs would provide a better understanding of cellular remodeling and adaptation in atherosclerosis. J. Cell. Physiol. 232: 7-13, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Kozaburo Hayashi
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan. .,Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan.
| | - Michitaka Higaki
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, Japan
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Wang X, Ye P, Cao R, Yang X, Xiao W, Zhang Y, Bai Y, Wu H. Triglycerides are a predictive factor for arterial stiffness: a community-based 4.8-year prospective study. Lipids Health Dis 2016; 15:97. [PMID: 27192979 PMCID: PMC4870778 DOI: 10.1186/s12944-016-0266-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 05/11/2016] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND Epidemiological studies have disclosed an independent effect of triglycerides on coronary heart disease despite achievement of low-density lipoprotein cholesterol goals with statin therapy. Arterial stiffness has been increasingly recognized as a strong predictor of cardiovascular disease and atherosclerotic disease. The association between triglycerides and arterial stiffness is not well characterized. We aimed to determine the relationship between triglycerides and arterial stiffness in a community-based longitudinal sample from Beijing, China. METHODS We related levels of plasma TGs to measures of arterial stiffness (carotid-femoral pulse wave velocity [PWV] and carotid-radial PWV) in 1447 subjects (mean age, 61.3 years) from a community-based population in Beijing, China. RESULTS After a median follow-up interval of 4.8 years, multiple linear regression analysis revealed that TGs were independently associated with carotid-femoral PWV (β = 0.747, P < 0.001) and carotid-radial PWV (β = 0.367, P = 0.001). In the group older than 65 years, the association between baseline TG levels and follow-up carotid-femoral PWV (β = 1.094, P = 0.001) and carotid-radial PWV (β = 0.524, P = 0.002) were strengthened. In forward stepwise multivariate logistic regression analysis, every SD increase in TGδ was associated with a 1.296-increased likelihood of the presence of carotid-femoral PWVδII (OR [per SD increase in TGδ]: 1.296; 95% CI: 1.064 ~ 1.580; P = 0.010) in Model 2, whereas the relationship between TGδ and carotid-radial PWVδII disappeared. In addition, the relationship was strengthened between TGδ and the presence of carotid-femoral PWVδII (OR 1.526, 95% CI: 1.088-2.141, P = 0.014) in the group older than 65 years but not carotid-radial PWVδII. No association was noted in subjects younger than 65 years. CONCLUSIONS Lower triglyceride levels were significantly associated with decreases in carotid-femoral PWV, indicating that achieving low TG levels may be an additional therapeutic consideration in subjects with atherosclerotic disease.
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Affiliation(s)
- Xiaona Wang
- Department of Geriatric Cardiology, Chinese PLA General Hospital, Fuxing Road #28, Beijing, 100853, China
| | - Ping Ye
- Department of Geriatric Cardiology, Chinese PLA General Hospital, Fuxing Road #28, Beijing, 100853, China.
| | - Ruihua Cao
- Department of Geriatric Cardiology, Chinese PLA General Hospital, Fuxing Road #28, Beijing, 100853, China
| | - Xu Yang
- Department of Geriatric Cardiology, Chinese PLA General Hospital, Fuxing Road #28, Beijing, 100853, China
| | - Wenkai Xiao
- Department of Geriatric Cardiology, Chinese PLA General Hospital, Fuxing Road #28, Beijing, 100853, China
| | - Yun Zhang
- Department of Geriatric Cardiology, Chinese PLA General Hospital, Fuxing Road #28, Beijing, 100853, China
| | - Yongyi Bai
- Department of Geriatric Cardiology, Chinese PLA General Hospital, Fuxing Road #28, Beijing, 100853, China
| | - Hongmei Wu
- Department of Geriatric Cardiology, Chinese PLA General Hospital, Fuxing Road #28, Beijing, 100853, China
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Clinical assessment of arterial stiffness with cardio-ankle vascular index: theory and applications. J Hypertens 2016; 33:1742-57; discussion 1757. [PMID: 26114836 DOI: 10.1097/hjh.0000000000000651] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Arterial stiffness is often assessed in clinical medicine, because it is not only an important factor in the pathophysiology of blood circulation but also a marker for the diagnosis and the prognosis of cardiovascular diseases. Many parameters have so far been proposed to quantitatively represent arterial stiffness and distensibility, such as pressure-strain elastic modulus (Ep), stiffness parameter (β), pulse wave velocity (PWV), and vascular compliance (Cv). Among these, PWV has been most frequently applied to clinical medicine. However, this is dependent on blood pressure at the time of measurement, and therefore it is not appropriate as a parameter for the clinical evaluation of arterial stiffness, especially for the studies on hypertension. On the contrary, stiffness parameter β is an index reflecting arterial stiffness without the influence of blood pressure. Recently, this parameter has been applied to develop a new arterial stiffness index called cardio-ankle vascular index (CAVI). Although this index is obtained from the PWV between the heart and the ankle, it is essentially similar to the stiffness parameter β, and therefore it does not depend on blood pressure changes during the measurements. CAVI is being extensively used in clinical medicine as a measure for the evaluation of cardiovascular diseases and risk factors related to arteriosclerosis. In the present article, we will explain the theoretical background of stiffness parameter β and the process to obtain CAVI. And then, the clinical utility of CAVI will be overviewed by reference to recent studies.
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Koniari I, Mavrilas D, Apostolakis E, Papadimitriou E, Papadaki H, Papalois A, Poimenidi E, Xanthopoulou I, Hahalis G, Alexopoulos D. Inhibition of Atherosclerosis Progression, Intimal Hyperplasia, and Oxidative Stress by Simvastatin and Ivabradine May Reduce Thoracic Aorta's Stiffness in Hypercholesterolemic Rabbits. J Cardiovasc Pharmacol Ther 2015; 21:412-22. [PMID: 26612090 DOI: 10.1177/1074248415617289] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 08/25/2015] [Indexed: 11/16/2022]
Abstract
AIMS This study aims to evaluate atherosclerosis, oxidative stress, and arterial stiffness attenuation by simvastatin and ivabradine in hyperlipidemic rabbits. METHODS AND RESULTS Forty rabbits were randomly divided into 4 groups: atherogenic diet (group C), atherogenic diet plus simvastatin (group S), atherogenic diet plus ivabradine (group I), and atherogenic diet plus simvastatin and ivabradine (group S + I). After 9 weeks, rabbits were euthanized and descending aortas excised for mechanical testing. Atherogenic diet induced the development of significant atherosclerotic lesions in group C animals but in none of groups S, I, and S + I. RAM-11 and HHF-35-positive cells were significantly reduced in groups S, I, and S + I compared with group C (P < .001). A significant neointimal hyperplasia and intima-media ratio reduction was demonstrated in groups S (P = .015 and P < .001), I (P = .021 and P < .001), and S + I (P = .019 and P < .001) compared with group C. Protein nitrotyrosine levels were significantly decreased in group S compared with group C (P = .009), and reactive oxygen species levels were decreased in group I compared with group C (P = .011). Aortic stiffness was significantly reduced in groups S, I, and S + I compared with group C (P = .003, P = .011, and P = .029). CONCLUSION Simvastatin and ivabradine significantly inhibited intimal hyperplasia and oxidative stress contributing to aortic stiffness reduction in hyperlipidemic rabbits.
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Affiliation(s)
- Ioanna Koniari
- Department of Cardiology, Patras University Hospital, Rion Patras, Greece
| | - Dimosthenis Mavrilas
- Laboratory of Biomechanics and Biomedical Engineering, Department of Mechanical Engineering & Aeronautics, University of Patras, Rion Patras, Greece
| | | | - Evangelia Papadimitriou
- Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, Patras, Greece
| | - Helen Papadaki
- Department of Anatomy, School of Medicine, University of Patras, Rion Patras, Greece
| | | | - Evangelia Poimenidi
- Laboratory of Molecular Pharmacology, Department of Pharmacy, University of Patras, Patras, Greece
| | | | - George Hahalis
- Department of Cardiology, Patras University Hospital, Rion Patras, Greece
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Next generation covered stents made from nanocomposite materials: A complete assessment of uniformity, integrity and biomechanical properties. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2015; 12:1-12. [PMID: 26238080 DOI: 10.1016/j.nano.2015.07.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Revised: 06/23/2015] [Accepted: 07/05/2015] [Indexed: 11/20/2022]
Abstract
Covered stents are stents wrapped with a thin polymeric membrane, and are typically used to treat vessel aneurysms and seal perforated arteries. Current covered stents suffer from restenosis due to limitations in material and fabrication methods which leaves metallic struts directly exposed to blood. We have developed a biocompatible and haemocompatible nanocomposite polymer, polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU). We devised a novel combination of ultrasonic spray atomisation system and dip-coating process to produce small calibre covered stents with metal struts fully embedded within the membrane, which also yields greater coating uniformity. Stent-polymer bonding was enhanced via silanisation and coating of reactive pre-polymer. Platelet studies supported the non-thrombogenicity of POSS-PCU. Biomechanical performances including diametrical compliance, bending strength, radial strength and recoil were evaluated and optimised. This proof-of-principle manufacturing technique could lead to the development of next-generation small calibre adult and paediatric covered stents. These stents are currently undergoing preclinical trial. From the Clinical Editor: The use of stents to treat vascular diseases is now the standard of care in the clinical setting. Nonetheless, a major problem of the current stents is the risk of restenosis and thrombosis. The authors developed a nanocomposite material using polyhedral oligomeric silsesquioxane and poly(carbonate-urea) urethane (POSS-PCU) and incorporated into metallic stents. Preliminary data have already shown promising results. It is envisaged that this would further lead to better stent technology in the future.
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Agianniotis A, Stergiopulos N. Wall properties of the apolipoprotein E-deficient mouse aorta. Atherosclerosis 2012; 223:314-20. [PMID: 22770991 DOI: 10.1016/j.atherosclerosis.2012.06.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2012] [Revised: 06/01/2012] [Accepted: 06/11/2012] [Indexed: 10/28/2022]
Abstract
OBJECTIVES We quantified the dysfunction of the aortic wall, determined structural and elastic properties, and provided histological data of the thoracic aortas of apolipoprotein E (apoE)-deficient mice which are used as model of atherosclerosis. METHODS Six young 10-12 week-old (apoE)-deficient mice of both sexes were studied and six age-matched C57BL/6J wild-type mice were used as control group. We performed extension-inflation mechanical tests at three different axial stretches (λ(z) = 1.6, 1.8, and 2.0), under maximally contracted or totally relaxed state of the vascular smooth muscle cells. Classical histology was performed to the arterial segments. RESULTS Control aortas were generally more distensible than the (apoE)-deficient mouse aortas under both relaxed and contracted smooth muscle. Also, aortas from (apoE)-deficient mice were stiffer (higher incremental elastic modulus) than control aortas. Control aortas exhibited a higher active diameter response compared to (apoE)-deficient mouse aortas, despite the fact that vascular smooth muscle cell density was increased by approximately 15% in the (apoE)-deficient mouse aortas. CONCLUSION We found substantial changes in the structural and elastic properties of the wall, in the active diameter response and in the histology of (apoE)-deficient mouse aortas compared to the control group. Our data can be used in the development of constituent-based models of the arterial wall and in studying the changes in arterial wall properties in presence of disease, such as atherosclerosis.
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Affiliation(s)
- Aristotelis Agianniotis
- Laboratory of Hemodynamics and Cardiovascular Technology, Institute of Bioengineering, Ecole Polytechnique Fédérale de Lausanne, BM 5128 (Bâtiment BM), Station 17, 1015 Lausanne, Switzerland.
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Koniari I, Mavrilas D, Papadaki H, Karanikolas M, Mandellou M, Papalois A, Koletsis E, Dougenis D, Apostolakis E. Structural and biomechanical alterations in rabbit thoracic aortas are associated with the progression of atherosclerosis. Lipids Health Dis 2011; 10:125. [PMID: 21791107 PMCID: PMC3160371 DOI: 10.1186/1476-511x-10-125] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2011] [Accepted: 07/26/2011] [Indexed: 11/19/2022] Open
Abstract
Background Atherosclerosis is a diffuse and highly variable disease of arteries that alters the mechanical properties of the vessel wall through highly variable changes in its cellular composition and histological structure. We have analyzed the effects of acute atherosclerotic changes on the mechanical properties of the descending thoracic aorta of rabbits fed a 4% cholesterol diet. Methods Two groups of eight male New Zealand White rabbits were randomly selected and fed for 8 weeks either an atherogenic diet (4% cholesterol plus regular rabbit chow), or regular chow. Animals were sacrificed after 8 weeks, and the descending thoracic aortas were excised for pressure-diameter tests and histological evaluation to examine the relationship between aortic elastic properties and atherosclerotic lesions. Results All rabbits fed the high-cholesterol diet developed either intermediate or advanced atherosclerotic lesions, particularly American Heart Association-type III and IV, which were fatty and contained abundant lipid-filled foam cells (RAM 11-positive cells) and fewer SMCs with solid-like actin staining (HHF-35-positive cells). In contrast, rabbits fed a normal diet had no visible atherosclerotic changes. The atherosclerotic lesions correlated with a statistically significant decrease in mean vessel wall stiffness in the cholesterol-fed rabbits (51.52 ± 8.76 kPa) compared to the control animals (68.98 ± 11.98 kPa), especially in rabbits with more progressive disease. Conclusions Notably, stiffness appears to decrease with the progression of atherosclerosis after the 8-week period.
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Affiliation(s)
- Ioanna Koniari
- Cardiothoracic Surgery Department, University Hospital of Patras, Patras, Greece.
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McKee CT, Last JA, Russell P, Murphy CJ. Indentation versus tensile measurements of Young's modulus for soft biological tissues. TISSUE ENGINEERING. PART B, REVIEWS 2011; 17:155-64. [PMID: 21303220 PMCID: PMC3099446 DOI: 10.1089/ten.teb.2010.0520] [Citation(s) in RCA: 393] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 02/07/2011] [Indexed: 12/21/2022]
Abstract
In this review, we compare the reported values of Young's modulus (YM) obtained from indentation and tensile deformations of soft biological tissues. When the method of deformation is ignored, YM values for any given tissue typically span several orders of magnitude. If the method of deformation is considered, then a consistent and less ambiguous result emerges. On average, YM values for soft tissues are consistently lower when obtained by indentation deformations. We discuss the implications and potential impact of this finding.
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Affiliation(s)
- Clayton T. McKee
- Department of Surgical and Radiological Science, School of Veterinary Medicine, University of California Davis, Davis, California
| | - Julie A. Last
- Department of Chemical and Biological Engineering, University of Wisconsin–Madison, Madison, Wisconsin
| | - Paul Russell
- Department of Surgical and Radiological Science, School of Veterinary Medicine, University of California Davis, Davis, California
| | - Christopher J. Murphy
- Department of Surgical and Radiological Science, School of Veterinary Medicine, University of California Davis, Davis, California
- Department of Ophthalmology and Vision Science, School of Medicine, University of California Davis, Davis, California
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Peloquin J, Huynh J, Williams RM, Reinhart-King CA. Indentation measurements of the subendothelial matrix in bovine carotid arteries. J Biomech 2011; 44:815-21. [PMID: 21288524 DOI: 10.1016/j.jbiomech.2010.12.018] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 12/16/2010] [Accepted: 12/17/2010] [Indexed: 10/18/2022]
Abstract
Artery biomechanics are an important factor in cardiovascular function and atherosclerosis development; as such, the macro-mechanics of whole arteries are well-characterized. However, much less is known about the mechanical properties of individual layers in the blood vessel wall. Since there is significant evidence to show that cells can sense the mechanical properties of their matrix, it is critical to characterize the mechanical properties of these individual layers at the scale sensed by cells. Here, we measured subendothelium mechanics in bovine carotid arteries using atomic force microscopy (AFM) indentation. To specifically indent the subendothelium, we evaluated three potential de-endothelialization methods: scraping, paper imprinting, and saponin incubation. Using scanning electron microscopy, histology stains, immunohistochemistry, and multiphoton microscopy, we found that scraping was the only effective de-endothelialization method capable of removing endothelial cells and leaving the subendothelial matrix largely intact. To determine the indentation modulus of the subendothelial matrix, both untreated and scraped (de-endothelialized) bovine carotid arteries were indented with a spherical AFM probe and the data were fit using the Hertz model. Both the endothelium on the untreated artery and the en face subendothelium had similar indentation moduli: E=2.5 ± 1.9 and 2.7 ± 1.1 kPa, respectively. These measurements are the first to quantify the micro-scale mechanics of the subendothelial layer, and constitute a critical step in understanding the relationship between altered subendothelial micromechanics and disease progression.
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Affiliation(s)
- John Peloquin
- Department of Biomedical Engineering, Cornell University, 302 Weill Hall, 526 Campus Road, Ithaca, NY 14853, USA
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Increases of Corporal Temperature as a Risk Factor of Atherosclerotic Plaque Instability. Ann Biomed Eng 2007; 36:66-76. [DOI: 10.1007/s10439-007-9397-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 10/19/2007] [Indexed: 11/26/2022]
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16
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Hamilton AJ, Kim H, Nagaraj A, Mun JH, Yan LL, Roth SI, McPherson DD, Chandran KB. Regional material property alterations in porcine femoral arteries with atheroma development. J Biomech 2005; 38:2354-64. [PMID: 16214483 DOI: 10.1016/j.jbiomech.2004.10.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2004] [Accepted: 10/13/2004] [Indexed: 10/25/2022]
Abstract
We have developed a novel methodology that permits assessment of regional vascular mechanical property alterations in the presence of atheroma in vivo employing a Yucatan miniswine model with induced lesions. Femoral arteries were imaged with intravascular ultrasound. Image data were segmented and, following three-dimensional reconstruction, underwent finite element and sensitivity analysis with optimization to identify regions with altered vascular mechanical properties. All regions were compared to histological analysis. In 12 animals with 8 weeks of endothelial cell denudation and high cholesterol diet (induced atherosclerosis), the elastic modulus initially decreased with early lesion development and then increased with increasing fibrosis-(elastic modulus-all values x10(4)Pa-mean+/-SEM) histologically normal (non-denuded control segment) elements 9.73+/-0.01, fatty elements 9.53+/-0.01, fibrofatty elements 9.41+/-0.03, and fibrous elements 9.68+/-0.02 (all p<0.001 vs. normal elements). Wall thickness, however, increased with atheroma formation. These data demonstrate decreasing vascular material properties with early lesions, followed by an increase as lesions progress. This methodology permits determination of areas with early atheroma development, follow atheroma progression, and potentially evaluate interventions aimed at decreasing atheroma load and normalizing vascular material properties.
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17
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Love M, Wray A, Worthington M, Ellis P. Failure of aneurysm sac shrinkage after endovascular repair; the effect of mural calcification. Clin Radiol 2005; 60:1290-4. [PMID: 16291310 DOI: 10.1016/j.crad.2005.05.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Revised: 05/23/2005] [Accepted: 05/25/2005] [Indexed: 10/25/2022]
Abstract
AIM To evaluate the effect of abdominal aortic aneurysm wall calcification on subsequent sac shrinkage after endovascular repair. MATERIALS AND METHODS Seventy-three patients underwent endovascular aneurysm repair. The degree of sac wall calcification on pre-procedural computed tomography (CT) examination was graded from 1 to 4 according to the degree of circumferential involvement. On follow-up CT imaging, the maximum transverse diameter (MTD) of the sac was recorded, as well as the presence or absence of endoleak. In those patients with a non-shrinking aneurysm, but no CT evidence of endoleak, contrast-enhanced ultrasound (USS) was performed. Any patient with an endoleak, however diagnosed, was excluded from the study. Kruskal-Wallis and Spearman's rank correlation coefficient testing was applied to compare the degree of calcification and change in MTD. RESULTS Sixty-three pre-procedural CT images were available for calcification grading. Six of this group had endoleaks resulting in 57 sets of data being available for the study. A reduction in MTD occurred in 68.25% of these patients by 1 year post-procedure. Our figures show aortic calcification is inversely associated with MTD reduction at 6 months (p = 0.01), 1 year (p = 0.05) and 2 years (p = 0.05). CONCLUSION This study indicates that the degree of aortic wall calcification is significant in predicting MTD reduction post-endovascular repair. The possible mechanisms and implications of this are discussed.
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Affiliation(s)
- M Love
- Department of Radiology, Royal Victoria Hospital, Belfast, UK.
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18
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Nagaraj A, Kim H, Hamilton AJ, Mun JH, Smulevitz B, Kane BJ, Yan LL, Roth SI, McPherson DD, Chandran KB. Porcine carotid arterial material property alterations with induced atheroma: an in vivo study. Med Eng Phys 2005; 27:147-56. [PMID: 15642510 DOI: 10.1016/j.medengphy.2004.09.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2004] [Revised: 09/01/2004] [Accepted: 09/29/2004] [Indexed: 10/26/2022]
Abstract
OBJECTIVE A novel methodology has been developed to evaluate regional alterations in arterial wall material properties with induced atheroma in an animal model. METHODS Atheromatous lesions (fatty, fibro-fatty, and fibrous) were induced in the carotid arteries of a Yucatan miniswine model by endothelial cell denudation and high cholesterol diet. The images at base line and 8 weeks after denudation were obtained using intravascular ultrasound (IVUS) imaging along with hemodynamic data. Finite element analysis (FEA) along with optimization was employed to assess regional alterations in elastic modulus in the presence of atheroma confirmed by histology. RESULTS In animals with 8 weeks of induced atherosclerosis, the elastic modulus increased-(elastic modulus-all values x 10(4) Pa, mean+/-S.D.) normal elements (9.34+/-0.36) compared to abnormal elements (9.52+/-0.36) (p<0.05 versus normal elements). Wall thickness increased with atheroma formation. These data demonstrate stiffening vascular wall elastic modulus with lesion progression. This is different from the behavior of femoral arteries, where the elastic modulus decreases with early stages of atheroma development followed by an increase as lesions progress. CONCLUSIONS This methodology permits determination of areas with early atheroma development, follow atheroma progression, and potentially evaluate interventions aimed at decreasing atheroma load and normalizing vascular material properties.
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Affiliation(s)
- Ashwin Nagaraj
- Department of Medicine, Northwestern University, Chicago, Illinois, USA
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19
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Ohashi T, Abe H, Matsumoto T, Sato M. Pipette aspiration technique for the measurement of nonlinear and anisotropic mechanical properties of blood vessel walls under biaxial stretch. J Biomech 2004; 38:2248-56. [PMID: 16154412 DOI: 10.1016/j.jbiomech.2004.09.019] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2002] [Accepted: 09/10/2004] [Indexed: 11/16/2022]
Abstract
A pipette aspiration technique was proposed for the measurement of nonlinear mechanical properties of arteries under biaxial stretching. A cross-shaped specimen of porcine thoracic aorta whose principal axes corresponded with the axial and circumferential directions of the aortic walls was excised. The intraluminal surface of the specimen was aspirated with a circular cross-sectioned glass pipette while the specimen was stretching in the axial and circumferential directions in 10% increments. The elastic modulus agreed with the incremental elastic modulus obtained through a conventional pressure-diameter test of the same specimen to within an error of 30% at a circumferential stretch ratio below 1.3 and an axial stretch ratio of 1.0, 1.1 or 1.2, which represent lower range of physiological stretch ratios for the porcine aorta. A rectangular cross-sectioned pipette was utilized to measure anisotropic properties of the specimen under biaxial stretching. When aspirated with such a pipette, the specimens' elastic properties along the length of the rectangular pipette cross section can be neglected. The elastic modulus was found to increase rapidly when the specimen was stretched in the direction of the pipette's width. Thus, pipette aspiration should have many advantages such as well measurement of the local nonlinear and anisotropic mechanical properties of blood vessel walls.
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Affiliation(s)
- Toshiro Ohashi
- Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Aramaki-Aoba-yama 6-6-01, Aoba-ku Sendai 980-8579, Japan.
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20
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Chandran KB, Mun JH, Choi KK, Chen JS, Hamilton A, Nagaraj A, McPherson DD. A method for in-vivo analysis for regional arterial wall material property alterations with atherosclerosis: preliminary results. Med Eng Phys 2003; 25:289-98. [PMID: 12649013 DOI: 10.1016/s1350-4533(02)00224-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Atherosclerosis is a diffuse arterial disease developing over many years and resulting in a complicated three-dimensional arterial morphology. The arterial wall material properties have been demonstrated to show regional alterations with atheroma development and growth. We present a mechanical analysis of diseased arterial segments reconstructed from intravascular ultrasound images in order to quantitatively identify regional alterations in the elastic constants with atherosclerotic lesions. We employ a finite element and a displacement sensitivity analysis to divide the arterial segment into regions with different material properties and use an optimization algorithm to identify the elastic constants in these regions. The results with regional variations identified with this method correlated qualitatively with the extent and location of atherosclerotic lesions identified by visual inspection of the affected arteries. The optimized elastic modulus in regions affected by early atherosclerotic lesions ranged from 90.9 to 93.0 kPa where as the corresponding magnitudes in normal arterial segments ranged from 97.9 to 101.0 kPa. This method can be potentially employed to identify the extent and location of atherosclerotic lesions in a systematic analysis and may potentially be used for the early detection of lesion growth.
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Affiliation(s)
- K B Chandran
- Department of Biomedical Engineering, University of Iowa, 1402 SC, Iowa City, Iowa, USA
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21
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Matsumoto T, Abe H, Ohashi T, Kato Y, Sato M. Local elastic modulus of atherosclerotic lesions of rabbit thoracic aortas measured by pipette aspiration method. Physiol Meas 2002; 23:635-48. [PMID: 12450265 DOI: 10.1088/0967-3334/23/4/304] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Changes in mechanical properties of arteries during atherogenesis remain controversial. One of the reasons could be that they have been evaluated with parameters measured in a whole vessel, although the lesions are localized. The local elastic modulus of atherosclerotic lesions was measured by the pipette aspiration method in thoracic aortas of rabbits fed a cholesterol diet for 8, 16, 24 and 28 weeks. The global elastic modulus of the whole aorta was measured by the pressure-diameter test. The local modulus decreased from that of the normal tissue in 8 weeks and then increased during the cholesterol feeding period. The global modulus did not change until 24 weeks and increased by 28 weeks. Histological observation revealed that the initial soft lesion was mainly composed of foam cells, and the stiffening accompanied first the appearance of smooth muscle cells in the top layer of the hyperplastic intima and then calcification in its bottom layer. The global elastic modulus did not change until marked calcification occurred in the tissue. These results suggest that change in mechanical properties of atherosclerotic lesion is not simple and has a close correlation with its histology. Assessment of local mechanical properties is important for studying mechanical properties of atherosclerotic arteries.
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Affiliation(s)
- Takeo Matsumoto
- Biomechanics Laboratory, Graduate School of Mechanical Engineering, Tohoku University, Aoba-yama 01, Sendai 980-8579, Japan.
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22
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Abstract
The goal of this study was to review the origin, clinical relevance and treatment of pulse pressure (PP). Elevated PP is increasingly being recognized as a risk factor for cardiovascular, particularly coronary, disease. Pulse pressure is discussed in terms of both Windkessel and distributive models of the arterial circulation. Pulse pressure arises from the interaction of cardiac ejection (stroke volume) and the properties of the arterial circulation. An increased stiffness of the aorta and large arteries leads to an increase in PP through a reduction in arterial compliance and effects on wave reflection. A number of factors are known to influence arterial wall behavior and, therefore, PP. In addition to the effects of aging and blood pressure on arterial wall elasticity, there is some evidence that atherosclerosis, per se, amplifies these effects. Thus, the relationship between PP and coronary disease may be bidirectional. A number of dietary and lifestyle interventions have been shown to modify large artery behavior. These include aerobic exercise training and consumption of n-3 fatty acids. Conversely, strength training is associated with an increase in arterial stiffness and a higher PP. The effects of antihypertensive medication have been extensively studied, but many studies are difficult to interpret because of concomitant change in blood pressure, and to a lesser degree, heart rate. However a number of studies do suggest direct arterial wall effects, particularly for angiotensin-converting enzyme inhibitors. A distributed compliance model of the arterial circulation provides a framework for understanding the causes, effects and potential treatment of elevations in PP.
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Affiliation(s)
- A M Dart
- Alfred Baker Medical Unit, Alfred Hospital and Baker Medical Research Institute, Melbourne, Australia.
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23
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Abstract
BACKGROUND Atherosclerosis causes over 40% of all deaths in the USA and Western Europe. Although several hypotheses have been proposed, the etiology and pathogenesis of the atherosclerosis remain unknown. OBJECTIVE To develop a model of selective coronary atherosclerosis in pigs. DESIGN An animal model of selective coronary atherosclerosis was developed by combining a guide-wire-induced endothelial injury and cholesterol-enriched diet. METHODS Twelve pigs were subjected to guide-wire-induced injury to endothelium of left anterior descending (LAD) coronary artery. Six animals (control group) were fed a standard pig food; the remaining six animals (cholesterol group) were fed a 6%-cholesterol-enriched diet. Three animals from the control group were killed immediately after the endothelial injury (acute control group). The other three animals in the control group (chronic control group) and all animals in the cholesterol-fed group were killed 4 weeks after the injury. RESULTS The endothelial surface and the media of the left circumflex coronary artery LCX in all animals were intact. Long eccentric areas of endothelial injury were found in the LAD coronary arteries of animals in the acute control group. Numerous fibrous atherosclerotic plaques in LAD coronary arteries were found in animals in the chronic control group as well as in animals in the cholesterol-fed group, but were highly pronounced in animals in the last group. No accumulation of lipids was found in the plaques of animals in both groups. CONCLUSIONS Administration of a 6%-cholesterol diet for 6 weeks is not sufficient to cause coronary atherosclerosis in pigs. Selective coronary atherosclerosis can be induced within 4 weeks with the same diet when the blood vessel has been injured with a guide wire.
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Affiliation(s)
- D Mihaylov
- Division of Artificial Organs, University of Groningen, The Netherlands.
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Hong MK, Vossoughi J, Mintz GS, Kauffman RD, Hoyt RF, Cornhill JF, Herderick EE, Leon MB, Hoeg JM. Altered compliance and residual strain precede angiographically detectable early atherosclerosis in low-density lipoprotein receptor deficiency. Arterioscler Thromb Vasc Biol 1997; 17:2209-17. [PMID: 9351391 DOI: 10.1161/01.atv.17.10.2209] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND This study was performed to detect changes in vascular biomechanical properties early in atherogenesis. METHODS AND RESULTS Age- and weight-matched LDL-receptor deficient Watanabe hypercholesterolemic male rabbits (Group I: n = 11) and normal rabbits (Group II: n = 11) were studied. Fasting plasma lipoprotein concentrations, aortic angiography and intravascular ultrasound, in vivo aortic compliance evaluation, ex vivo aortic residual strain measurements, aortic lipid content and histopathology were determined. Plasma cholesterol was increased 9.8 fold and aortic cholesterol content was increased from 20 to 43 fold in Group I compared to Group II, respectively (P < .00005). Angiography revealed no stenoses in either group, whereas intravascular ultrasound and histological studies of Group I showed small circumferential plaques with < 10% cross-sectional area involvement. The residual strain in Group I was significantly increased in the ascending thoracic aorta (22.1 +/- 6.9% versus 10.4 +/- 3.2% in Group II, P < .0001), descending thoracic aorta (15.7 +/- 7.2% versus 4.8 +/- 1.3% in Group II, P < .0001), and abdominal aorta (18.0 +/- 4.8% versus 8.3 +/- 6.3% in Group II, P < .005). Changes in residual strain were inversely correlated with the aortic cholesterol content in the ascending thoracic aorta (r = -.72; P = -.001), descending thoracic aorta (r = -.95; P < .001), and abdominal aorta (r = -.51; P = .019). CONCLUSIONS Early atherosclerosis in LDL-receptor deficient rabbits, undetectable by angiography yet observed by intravascular ultrasound imaging and histology, is associated with marked changes in ex vivo residual strain. Alterations in vascular biomechanical properties, associated with changes in cholesterol content, may have physiologic consequences and may be useful in detecting and quantitating early atherosclerosis.
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Affiliation(s)
- M K Hong
- Department of Internal Medicine (Cardiology Division), Washington Hospital Center, Washington, DC, USA
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25
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Hayashi K, Imai Y. Tensile property of atheromatous plaque and an analysis of stress in atherosclerotic wall. J Biomech 1997; 30:573-9. [PMID: 9165390 DOI: 10.1016/s0021-9290(96)00185-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
To know the contributions of blood pressure induced stress to the progression of atherosclerosis and the rupture of atheroma, cross-sectional distributions of stresses in atherosclerotic walls were calculated by finite element method, using stress-strain data of aortic walls and atherosclerotic plaques obtained from hypercholesterolemic rabbits. In the aortic wall attached by a local plaque, circumferential tensile stress was maximal in the wall near plaque edge, and the stress value was very high compared to the tensile strength of wall media. This local stress concentration may be a contributing factor to the progression of atherosclerotic disease. In the aortic wall uniformly lined with atheroma, circumferential stress was high in the innermost layer of atheroma, and its magnitude was comparable to the tensile strength of plaque. Stress gradient at the interface between atheroma and wall was also high. These results indicate a possibility of rupture of atheroma near the intraluminal surface of atheroma or at the junction of atheroma with wall intima.
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Affiliation(s)
- K Hayashi
- Department of Mechanical Engineering, Faculty of Engineering Science, Osaka University, Japan
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26
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Matsumoto T, Hayashi K, Ide K. Residual strain and local strain distributions in the rabbit atherosclerotic aorta. J Biomech 1995; 28:1207-17. [PMID: 8550639 DOI: 10.1016/0021-9290(94)00179-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Effect of atherosclerosis on the residual strain in the arterial wall was studied in the rabbit thoracic aorta. Atherosclerosis was induced by feeding a cholesterol diet or by combining denudation of aortic endothelial cells with the diet feeding. Diameter of each aorta in the physiological state was determined from a static pressure-diameter test. A ring specimen was obtained from the position where the diameter was measured. After the measurement of its no-load diameters, the ring was cut radially to measure the opening angle. Histological section was then obtained from the opened-up ring specimen. The section was divided into 32 subsections and local dimensions were measured for each subsection. Residual and in vivo strains referring to the opened-up configuration were calculated from the local dimensions and the diameters in the unloaded and physiological states. The opening angle significantly correlated with the area fraction of intimal hyperplasia until severe calcification occurred, while it had a negative correlation with the area fraction of calcified region. Histological observation of opened-up ring specimens indicated that the media adjacent to hyperplastic intima remained stretched, while that away from the intima relaxed. Analysis of local strains showed that, in the atherosclerotic aorta without calcification, higher residual strain (compressive), i.e., lower in vivo strain (tensile), appears in the thicker intima. These results suggest that: (a) intimal hyperplasia increases residual strain and thus reduces the in vivo strain exerted in the intima and (b) calcified tissue restrains the deformation of adjacent tissues. The intimal hyperplasia and the calcification may complicate strain fields in the atherosclerotic aorta.
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Affiliation(s)
- T Matsumoto
- Department of Mechatronics and Precision Engineering, Faculty of Engineering, Tohoku University, Sendai, Japan
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