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Journal of the Mechanical Behavior of... Jun 2022Healthy human descending thoracic aortas, obtained during organ donation for transplant and research, were tested in a mock circulatory loop to measure the mechanical...
Healthy human descending thoracic aortas, obtained during organ donation for transplant and research, were tested in a mock circulatory loop to measure the mechanical response to physiological pulsatile pressure and flow. The viscoelastic properties of the aortic segments were investigated at three different pulse rates. The same aortic segments were also subjected to quasi-static pressure tests in order to identify the aortic dynamic stiffness ratio, which is defined as the ratio between the stiffness in case of pulsatile pressure and the stiffness measured for static pressurization, both at the same value of pressure. The loss factor was also identified. The shape of the deformed aorta under static and dynamic pressure was measured by image processing to verify the compatibility of the end supports with the natural deformation of the aorta in the human body. In addition, layer-specific experiments on 10 human descending thoracic aortas allowed to precisely identify the mass density of the aortic tissue, which is an important parameter in cardiovascular dynamic models.
Topics: Aorta; Aorta, Thoracic; Humans; Models, Cardiovascular; Vascular Stiffness; Viscosity
PubMed: 35390678
DOI: 10.1016/j.jmbbm.2022.105205 -
Science (New York, N.Y.) Oct 2009
Topics: Animals; Aorta; Arteries; Blood Circulation; Cell Movement; Endothelial Cells; Ephrin-B2; Lymphatic Vessels; Mice; Morphogenesis; Neovascularization, Physiologic; Receptor, EphB4; Signal Transduction; Stem Cells; Veins; Zebrafish; Zebrafish Proteins
PubMed: 19815764
DOI: 10.1126/science.1181033 -
Journal of Comparative Physiology. B,... Jan 2020Cardiovascular diseases (CVD) are one of the most common causes of mortality likely genetically linked to the variation in basal metabolic rate (BMR). A robust test of...
Cardiovascular diseases (CVD) are one of the most common causes of mortality likely genetically linked to the variation in basal metabolic rate (BMR). A robust test of the significance of such association may be provided by artificial selection experiments on animals selected for diversification of BMR. Here we asked whether genetically determined differences in BMR correlate with anatomical shift in endothelium structure and if so, the relaxation and contraction responses of the aorta in mice from two lines of Swiss-Webster laboratory mice (Mus musculus) divergently selected for high or low BMR (HBMR and LBMR lines, respectively). Functional and structural study of aorta showed that a selection for divergent BMR resulted in the between-line difference in diastolic aortic capacity. The relaxation was stronger in aorta of the HBMR mice, which may stem from greater flexibility of aorta mediated by higher activity of Ca-activated K channels. Structural examination also indicated that HBMR mice had significantly thicker aorta's middle layer compared to LBMR animals. Such changes may promote arterial stiffness predisposing to cardiovascular diseases. BMR-related differences in the structure and relaxation ability of aortas in studied animals may be reminiscent of potential risk factors in the development of CVD in humans.
Topics: Animals; Aorta; Basal Metabolism; Body Weight; Endothelium; Male; Mice; Potassium Channels, Calcium-Activated
PubMed: 31873784
DOI: 10.1007/s00360-019-01252-6 -
The Annals of Thoracic Surgery Nov 2020Conflicting data exist regarding the impact of ascending aorta size on outcomes after the Norwood procedure. Results from multi-institutional studies have largely relied...
BACKGROUND
Conflicting data exist regarding the impact of ascending aorta size on outcomes after the Norwood procedure. Results from multi-institutional studies have largely relied on heterogeneous populations undergoing this surgery for different anatomic defects. Using data from the Single Ventricle Reconstruction Trial, we analyzed the impact of preoperative ascending aortic diameter on Norwood outcomes for patients with aortic atresia variants of hypoplastic left heart syndrome.
METHODS
Neonates with aortic atresia and no ventricular septal defect were included and classified into four groups, based on their baseline ascending aorta echocardiographic measurements: less than or equal to 1.5 mm, 1.6 to 1.9 mm, 2.0 to 3.9 mm, and greater than or equal to 4.0 mm. Outcomes included 14-day mortality, transplant-free survival at 1 and 14 months, need for extracorporeal membrane oxygenation, length of ventilation, intensive care, and hospital stay, intensive care unit (ICU)-free days, right ventricular function, and incidence of recoarctation by 14 months.
RESULTS
Overall, 292 patients were analyzed. Median length of ICU stay was significantly longer for infants with small aortas, and ICU-free days were significantly lower. There was no difference in length of mechanical ventilation or hospitalization between groups. Long-term right ventricular function and tricuspid regurgitation did not differ. Aortic arch recoarctation incidence was higher in patients with small aortic diameters. Patients with aortas less than or equal to 1.5 mm had decreased 30-day transplant-free survival.
CONCLUSIONS
Infants with aortic atresia variants of hypoplastic left heart syndrome and baseline ascending aortic diameter less than or equal to 1.5 mm appear to suffer the greatest morbidity and mortality early after Norwood procedure. These infants also experienced longer stays in the ICU and higher rates of recoarctation. Ascending aortic diameter does not appear to affect long-term ventricular function.
Topics: Aorta; Aortic Coarctation; Child; Child, Preschool; Echocardiography; Extracorporeal Membrane Oxygenation; Female; Humans; Hypoplastic Left Heart Syndrome; Intensive Care Units; Length of Stay; Male; Norwood Procedures; Respiration, Artificial
PubMed: 32213312
DOI: 10.1016/j.athoracsur.2020.02.037 -
Rheumatology (Oxford, England) Nov 2022To validate in a large cohort with right-sided aorta the theory that thoracic right-sided flowing osteophytes in DISH results from a 'protective' effect of the pulsating...
OBJECTIVES
To validate in a large cohort with right-sided aorta the theory that thoracic right-sided flowing osteophytes in DISH results from a 'protective' effect of the pulsating descending left-sided thoracic aorta.
METHODS
Chest CTs of patients with DISH and right-sided aorta and controls with DISH and left-sided aorta were evaluated and compared on each intervertebral space (IS) for the location of the aorta (right, left, centre) and the location of the osteophyte relative to the aorta (contralateral, ipsilateral, bilateral).
RESULTS
The study and control cohorts included 31 and 35 subjects, respectively (male 22/9 and female 27/8; median age 64.8/65.3 years; P = 0.86). Osteophytes contralateral to the aorta's location were recorded in the majority of ISs in both the study and control groups (47% and 60%, respectively; P > 0.05), while ipsilateral osteophytes were recorded in 6.9% and 7.7%, respectively (P = 0.002). Bilateral osteophytes located to the right and the left of the aorta were significantly more prevalent in the study group compared with the controls (17.2% and 5.4%, respectively; P = 0.04).
CONCLUSIONS
Aortic pulsation plays an important role in inhibiting the development of osteophytes and results in the majority of contralateral osteophytes on both right-sided and left-sided aortas. However, since both ipsilateral and bilateral osteophytes were not at all rare in both groups, other parameters, which are yet to be established, probably contribute to the location of osteophytes.
Topics: Humans; Male; Female; Middle Aged; Osteophyte; Hyperostosis, Diffuse Idiopathic Skeletal; Spine; Aorta; Aorta, Thoracic
PubMed: 35353143
DOI: 10.1093/rheumatology/keac183 -
Biomechanics and Modeling in... Feb 2021The compliance of the proximal aortic wall is a major determinant of cardiac afterload. Aortic compliance is often estimated based on cross-sectional area changes over...
The compliance of the proximal aortic wall is a major determinant of cardiac afterload. Aortic compliance is often estimated based on cross-sectional area changes over the pulse pressure, under the assumption of a negligible longitudinal stretch during the pulse. However, the proximal aorta is subjected to significant axial stretch during cardiac contraction. In the present study, we sought to evaluate the importance of axial stretch on compliance estimation by undertaking both an in silico and an in vivo approach. In the computational analysis, we developed a 3-D finite element model of the proximal aorta and investigated the discrepancy between the actual wall compliance to the value estimated after neglecting the longitudinal stretch of the aorta. A parameter sensitivity analysis was further conducted to show how increased material stiffness and increased aortic root motion might amplify the estimation errors (discrepancies between actual and estimated distensibility ranging from - 20 to - 62%). Axial and circumferential aortic deformation during ventricular contraction was also evaluated in vivo based on MR images of the aorta of 3 healthy young volunteers. The in vivo results were in good qualitative agreement with the computational analysis (underestimation errors ranging from - 26 to - 44%, with increased errors reflecting higher aortic root displacement). Both the in silico and in vivo findings suggest that neglecting the longitudinal strain during contraction might lead to severe underestimation of local aortic compliance, particularly in the case of women who tend to have higher aortic root motion or in subjects with stiff aortas.
Topics: Adolescent; Adult; Aorta; Biomechanical Phenomena; Compliance; Computer Simulation; Female; Humans; Magnetic Resonance Angiography; Magnetic Resonance Imaging; Male; Models, Cardiovascular; Motion; Pressure
PubMed: 32737630
DOI: 10.1007/s10237-020-01371-y -
European Spine Journal : Official... Mar 2019Detailed knowledge of the anatomy of the thoracic aorta is crucial for thoracolumbar spinal surgery. The purpose of the present study is to describe the relative...
PURPOSE
Detailed knowledge of the anatomy of the thoracic aorta is crucial for thoracolumbar spinal surgery. The purpose of the present study is to describe the relative displacement of the aorta to the spine in supine, prone and prone position with padding. Improved understanding of the magnitude and direction of this often-overlooked change could benefit preoperative planning and decision-making.
METHODS
A total of 200 patients underwent CT scan of the thoracic spine in the standard supine, prone and prone position with padding. Axial CT images from T4 to T12, in all three different positions, were selected and the following parameters were measured: (a) distance B connecting left pedicle entry point to the edge of the aortic wall and (b) projections Bx and By, representing the minimum AP depth and horizontal displacement of the aortic wall relative to the left pedicle entry point O.
RESULTS
There was a significant difference in the distance B between the three different positions across all thoracic vertebrae levels, confirming that positioning significantly affects aorta's relative position. Moreover, in the prone position with padding at the level of T6, the aortic wall lies at a minimum distance from the left pedicular axis and thus from the typical screw trajectory.
CONCLUSION
The results of this study show that prone positioning for posterior thoracolumbar approach affects significantly the anatomic relationship of the aorta to the spine. Surgeons should be aware that standard supine CT evaluation represents a static technique, which can differ considerably from surgical reality. These slides can be retrieved from electronic supplementary material.
Topics: Aorta; Humans; Patient Positioning; Prone Position; Supine Position; Thoracic Vertebrae; Tomography, X-Ray Computed
PubMed: 30430251
DOI: 10.1007/s00586-018-5812-9 -
Tissue Engineering. Part C, Methods Jan 2017Decellularization of tissues and organs has high potential to obtain unique conformation and composition as native tissue structure but may result in weakened tissue...
Decellularization of tissues and organs has high potential to obtain unique conformation and composition as native tissue structure but may result in weakened tissue mechanical strength. In this study, poly(glycerol-sebacate) (PGS) elastomers were combined with decellularized aorta fragments to investigate the changes in mechanical properties. PGS prepolymer was synthesized via microwave irradiation and then in situ crosslinked within the decellularized aorta extracellular matrix (ECM). Tensile strength (σ) values were found comparable as 0.44 ± 0.10 MPa and 0.57 ± 0.18 MPa for native and hybrid aorta samples, respectively, while elongation at break (ɛ) values were 261% ± 17%, 7.5% ± 0.57%, and 22.18% ± 2.48% for wet control (native), decellularized dried aortae, and hybrid matrices, showing elastic contribution. Young's modulus data indicate that there was a threefold decrease in stiffness compared to decellularized samples once PGS is introduced into the ECM structure. Scanning electron microscopy (SEM) analysis of hybrid grafts revealed that the construct preserves porosity in medial layer of the vessel. Biocompatibility analyses showed no cytotoxic effects on human abdominal aorta smooth muscle cells. Cell studies showed 98% activity in hybrid graft extracts. As a control, collagen coating of the hybrid grafts was performed in the recellularization stage. SEM analysis of recellularized hybrid grafts revealed that cells were attached to the surface of the hybrid graft and proliferated during the 14 days of culture in both groups. This study shows that introducing an elastomer into the native ECM structure following decellularization process can be a useful approach for the preparation of mechanically enhanced composites for soft tissues.
Topics: Animals; Aorta; Cells, Cultured; Cross-Linking Reagents; Decanoates; Elastomers; Extracellular Matrix; Glycerol; Humans; Materials Testing; Microscopy, Electron, Scanning; Myocytes, Smooth Muscle; Polymers; Porosity; Sheep; Tensile Strength; Tissue Engineering
PubMed: 27875930
DOI: 10.1089/ten.TEC.2016.0375 -
IEEE Transactions on Bio-medical... Mar 2023The need for distilling the hemodynamic complexity of aortic flows into clinically relevant quantities resulted in a loss of the information hidden in 4D aortic fluid...
OBJECTIVE
The need for distilling the hemodynamic complexity of aortic flows into clinically relevant quantities resulted in a loss of the information hidden in 4D aortic fluid structures. To reduce information loss, this study proposes a network-based approach to identify and characterize in vivo the large-scale coherent motion of blood in the healthy human aorta.
METHODS
The quantitative paradigm of the aortic flow as a "social network" was applied on 4D flow MRI acquisitions performed on forty-one healthy volunteers. Correlations between the aortic blood flow rate waveform at the proximal ascending aorta (AAo), assumed as one of the drivers of aortic hemodynamics, and the waveforms of the axial velocity in the whole aorta were used to build "one-to-all" networks. The impact of the driving flow rate waveform and of aortic geometric attributes on the transport of large-scale coherent fluid structures was investigated.
RESULTS
The anatomical length of persistence of large-scale coherent motion was the 29.6% of the healthy thoracic aorta length (median value, IQR 23.1%-33.9%). Such length is significantly influenced by the average and peak-to-peak AAo blood flow rate values, suggesting a remarkable inertial effect of the AAo flow rate on the transport of large-scale fluid structures in the distal aorta. Aortic geometric attributes such as curvature, torsion and arch shape did not influence the anatomical length of persistence.
CONCLUSION
The proposed in vivo approach allowed to quantitatively characterize the transport of large-scale fluid structures in the healthy aorta, strengthening the definition of coherent hemodynamic structures and identifying flow inertia rather than geometry as one of its main determinants.
SIGNIFICANCE
The findings on healthy aortas may be used as reference values to investigate the impact of aortic disease or implanted devices in disrupting/restoring the physiological spatiotemporal coherence of large-scale aortic flow.
Topics: Humans; Aortic Valve; Blood Flow Velocity; Aorta; Magnetic Resonance Imaging; Aorta, Thoracic
PubMed: 36155431
DOI: 10.1109/TBME.2022.3209736 -
Clinical and Investigative Medicine.... Aug 1994Dissecting aneurysms split the wall of the aorta and other large arteries to create a false lumen in parallel with the true lumen. Experiments were designed to determine...
Dissecting aneurysms split the wall of the aorta and other large arteries to create a false lumen in parallel with the true lumen. Experiments were designed to determine the pressure required to tear the media and the work required per unit area to propagate the dissection once it started. India ink was injected into the media of 17 opened porcine aortas through a needle inserted parallel to the lumen of opened aortas placed in a saline bath. The ink was infused at 0.9 ml/min with a constant infusion pump as the pressure was monitored with a pressure transducer. The size of the bleb formed by the ink in the media was recorded with a video camera mounted perpendicular to the lumenal surface. All data were recorded on a computer. The pressure-volume curve was used to obtain the distensibility of the media (the upslope), the peak pressure, the tearing pressure, and the work of dissection (the area under the P-V curve once tearing occurred). The projected area of the bleb was calculated from the video images, and the work/area was calculated. The peak pressures were always extremely high, and ranged from 634 +/- 204 (SD) mmHg for the lower abdominal aorta to 816 +/- 145 mmHg for the lower thoracic aorta. The work/area ranged from 1.88 +/- 0.89 mJ/cm2 for the upper abdominal aorta to 11.34 +/- 4.05 mJ/cm2 for the lower abdominal aorta. An ANOVA showed that the lower abdominal aorta tore at lower pressures initially, but required much more energy to propagate the dissection. We believe that this is because of structural differences in the elastin pattern in the abdominal aorta.
Topics: Animals; Aorta; Aorta, Abdominal; Aorta, Thoracic; Elastin; Microscopy, Electron, Scanning; Pressure; Swine; Tensile Strength
PubMed: 7982294
DOI: No ID Found