Positional variations in fracture toughness, stiffness and strength of descending thoracic pig aorta (original) (raw)
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Mechanical Properties of Porcine Aorta – Influence of Specimen Taken Orientation
Advances in Intelligent Systems and Computing, 2019
The aim of the work was a characteristic of anisotropic mechanical properties of a pig's aorta. The isolated ascending, descending and thoracic aortas were taken. The longitudinal and transversal orientations of specimens taken were considered. Tissue strips were cut in the longitudinal orientation and in the transversal orientation as rings. Part of the rings was cut and indicated as the transversal strip samples, the second part in the form of rings was indicated as the transversal ring samples. The prepared samples were tested in an uniaxial tensile test. The values of the maximal force, the elongation, the ultimate tensile strength and strain at the UTS, Young's moduli and energy of destruction were estimated. The influence of orientation of samples taking was estimated. The highest values of the maximal force and the UTS were determined for the transversal ring samples and the lowest for the longitudinal strip samples.
Journal of the mechanical behavior of biomedical materials, 2015
Determination of correlations between transmural mechanical and morphological properties of aorta would provide a quantitative baseline for assessment of preventive and therapeutic strategies for aortic injuries and diseases. A multimodal and multidisciplinary approach was adopted to characterize the transmural morphological properties of descending porcine aorta. Histology and multi-photon microscopy were used for describing the media layer micro-architecture in the circumferential-radial plane, and Fourier Transform infrared imaging spectroscopy was utilized for determining structural protein, and total protein content. The distributions of these quantified properties across the media thickness were characterized and their relationship with the mechanical properties from a previous study was determined. Our findings indicate that there is an increasing trend in the instantaneous Young׳s modulus (E), elastic lamella density (ELD), structural protein (SPR), total protein (TPR), and ...
Mechanical properties of rat thoracic and abdominal aortas
Journal of Biomechanics, 2008
Mechanical properties of abdominal and thoracic arteries of 2 mm in diameter were determined from adults Wistar rats. A tensile testing instrument was used to obtain stress/strain curves with arteries immersed in physiological buffer at 37 1C. A displacement was applied on all arteries with various frequencies (1-7.5 Hz) and strains (5-60%). From each curve a Young modulus was obtained using a mathematical model based on a nonlinear soft tissue model. No influence of frequency on modulus was evidenced in the tested range. Abdominal aortas, which were found slightly thicker than thoracic aortas, were characterized by a higher modulus. Due to the interest of decellularized biological materials, we also used SDS/Triton treated arteries, and found that the chemical treatment increased modulus of thoracic arteries. Tensile tests were also performed on thoracic aortas in the longitudinal and transversal directions. Longitudinal moduli were found higher than transversal moduli and the difference could be related to the longitudinal orientation of collagen fibers. These data and mathematical model seem useful in the design of new vascular synthetic or biological prostheses for the field of tissue engineering. r
Assessing the Homogeneity of the Elastic Properties and Composition of the Pig Aortic Media
Journal of Vascular Research, 2001
Most previous studies of arterial wall elasticity and rheology have assumed that the properties of the wall are uniform across the thickness of the media and, therefore, that the relationship between stress and strain may be described by a constitutive equation based on a single strain energy function. The few studies where this assumption has been questioned, focussed on differences between the adventitia and the media rather than on differences within the media itself. Here, we report in vitro elasticity and residual strain measurements performed separately on the inner and outer half of the pig aortic media, together with a histomorphometric assessment of the radial distribution of elastin, collagen and smooth muscle cell numbers. Although we found that the pressure-diameter relationships of the two halves were dissimilar, when allowance was made for their different unloaded dimensions, their material properties agreed closely, a result in keeping with the observed uniform radial...
The importance of collagen composition and biomechanics for the porcine aortic root
Journal of biomechanics, 2020
A thorough understanding of the aortic root structure and biomechanics is necessary when performing aortic valve-sparing procedures in patients with aortic root aneurysms. This study aimed to evaluate the amount of collagen and biomechanics at different levels and segments of the aortic root. Ten aortic roots from healthy pigs were excised including the aortic annulus, the sinuses of Valsalva, and the sinotubular junction (STJ). Specimens were further divided into three circumferential segments; left coronary (LC)-, right coronary (RC)-, and non-coronary (NC) sinus. Collagen was determined using hydroxyproline analysis and specimens were tested biomechanically for stress-strain relations. The annulus showed significantly larger average maximum stiffness (9.6 ± 4.5 N/mm) compared with the sinus (4.5 ± 2.0 N/mm) and STJ (4.8 ± 1.8 N/mm). The average collagen content was likewise higher in the annulus (4.0 ± 1.0 mg/ml) compared with the sinus (2.4 ± 0.6 mg/ml) and STJ (2.2 ± 0.5 mg/ml)...
Segmental Variations in the Peel Characteristics of the Porcine Thoracic Aorta
Annals of Biomedical Engineering, 2020
Aortic dissection occurs predominantly in the thoracic aorta and the mechanisms for the initiation and propagation of the tear in aortic dissection are not well understood. We study the tearing characteristics of the porcine thoracic aorta using a peeling test and we estimate the peeling energy per unit area in the ascending and the descending segments. The stretch and the peel force per unit width undergone by the peeled halves of a rectangular specimen are measured. We find that there can be significant variation in the stretch within the specimen and the stretch between the markers in the specimen varies with the dynamics of peeling. We found that in our experiment the stretch achieved in the peeled halves was such that it was in the range of the stretch at which the stress-stretch curve for the uniaxial experiment starts deviating from linearity. Higher peeling energy per unit area is required in the ascending aorta compared to the descending aorta. Longitudinal specimens required higher peeling energy per unit area when compared to the circumferential specimens.
Journal of applied biomaterials & biomechanics (JABB)
Surgical interventions on the arterial wall can produce modifications to its tissue characteristics, and the addition of synthetic materials of different types can have implications on hemodynamics and blood vessel wall behavior. This work studies the midterm effects of end-to-end anastomosis (E/E), Gore-tex graft interposition (GGI) and Gore-tex patch graft aortoplasty (GPGA) in aortic arch reconstruction. The study comprised of two groups of healthy Danish sows. The sows in the first group (short term (ST)) weighed about 40 kg, underwent a surgical operation and were sacrificed on the same day. The sows in the second group (midterm (MT)) weighed 5-10 kg, underwent a surgical operation and were then allowed to grow to a weight of about 30-40 kg, before being sacrificed. One sow in each group was scheduled for E/E and one sow for GGI. One sow in ST and two sows in MT received GPGA. The overall average wall thickness was 1.93 mm. Relaxation constant values were significantly higher f...
Comparative Analysis of Porcine and Human Thoracic Aortic Stiffness
European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery, 2018
To compare porcine and human thoracic aortic stiffness using the available literature. The available literature was searched for studies reporting data on porcine or human thoracic aortic mechanical behaviour. A four fibre constitutive model was used to transform the data from included studies. Thus, equi-biaxial stress stretch curves were generated to calculate circumferential and longitudinal aortic stiffness. Analysis was performed separately for the ascending and descending thoracic aorta. Data on human aortic stiffness were divided by age <60 or ≥60 years. Porcine and human aortic stiffness were compared. Eleven studies were included, six reported on young porcine aortas, four on human aortas of various ages, and one reported on both. In the ascending aorta, circumferential and longitudinal stiffness were 0.42±0.08 MPa and 0.37±0.06 MPa for porcine aortas (4-9 months) versus 0.55±0.15 MPa and 0.45±0.08 MPa for humans <60 years, and 1.02±0.59 MPa and 1.03±0.54 MPa for huma...
Artery Research
Aortic diseases are a significant cardiovascular health problem and occur in different ways across the vascular tree. Investigation of the mechanical properties of the aorta is important for better understanding of aortic diseases. In this study, the biomechanical and biochemical properties of the ovine aorta have been comprehensively mapped across different regions from the ascending to the abdominal aorta. We have determined the mechanical properties at the macro-(via tensile testing) and at the micro-scale (via oscillatory nanoindentation). Uniaxial tensile testing was conducted on circumferential strips for the ascending, upper thoracic region and upper abdominal region to determine physiological elastic modulus, tangent modulus at 0.5 strain, and the maximum elastic modulus. Nanoindentation was conducted on the medial layer (tissue cross-section) and intimal and adventitial face (longitudinal orientation) to determine the shear storage (G′) and shear loss modulus (G″). All of the measured mechanical properties increased with distance from the heart. For example, G′ increased by 237.1% and 275.3% for the intimal face and adventitial face, respectively. In parallel, collagen, glycosaminoglycans (GAG) and elastin levels were also measured across the entire length of the ovine aorta. The mechanical properties correlated with increasing collagen, and decreasing GAG and elastin. Collagen increased by 147.2% whereas GAG (−120.3%) and elastin decreased (−78.2%). These findings have relevance for developing mechanistic insight into aortic aneurysms and dissections.
2013
Knowledge of the structural organization of the aortic tunica media is important in understanding the physicomechanical properties and alterations which underpin aortic aging and pathologies such as atherosclerosis, aneurysms and aortitis. Recent studies have cast doubt on the exclusivity of the medial lamella unit and musculoelastic fascicle concepts of the aortic structure. The goat is a suitable model for studying cardiovascular disease. Therefore the structure of tunica media of its aorta was studied by transmission electron microscopy. Materials were obtained from 6 healthy adult male goats [age range 12 – 24 months]. Specimens from the mid thoracic aortic segment were fixed in 3% phosphate buffered glutaraldehyde and processed for durcupan embedding and sectioning. Ultrathin sections were stained with uranyl acetate, counterstained in lead citrate and examined by Philips 210 transmission electron microscope. Besides medial lamella units and musculoelastic fascicles in the tuni...