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Journal of Cardiovascular Translational... Oct 2022Aortic surgeries in congenital conditions, such as hypoplastic left heart syndrome (HLHS), aim to restore and maintain the conduit and reservoir functions of the aorta....
Aortic surgeries in congenital conditions, such as hypoplastic left heart syndrome (HLHS), aim to restore and maintain the conduit and reservoir functions of the aorta. We proposed a method to assess these two functions based on 4D flow MRI, and we applied it to study the aorta in pre-Fontan HLHS. Ten pre-Fontan HLHS patients and six age-matched controls were studied to derive the advective pressure difference and viscous dissipation for conduit function, and pulse wave velocity and elastic modulus for reservoir function. The reconstructed neo-aorta in HLHS subjects achieved a good conduit function at a cost of an impaired reservoir function (69.7% increase of elastic modulus). The native descending HLHS aorta displayed enhanced reservoir (elastic modulus being 18.4% smaller) but impaired conduit function (three-fold increase in peak advection). A non-invasive and comprehensive assessment of aortic conduit and reservoir functions is feasible and has potentially clinical relevance in congenital vascular conditions.
Topics: Humans; Aorta, Thoracic; Pulse Wave Analysis; Hypoplastic Left Heart Syndrome; Aorta
PubMed: 35199256
DOI: 10.1007/s12265-022-10221-4 -
Frontiers in Bioscience (Landmark... Jan 2012Vacuum freeze-dried blood is a good material for vascular grafts. However, studies on this technology are few, particularly on physical performance change of... (Review)
Review
Vacuum freeze-dried blood is a good material for vascular grafts. However, studies on this technology are few, particularly on physical performance change of freeze-dried blood vessel at different pre-freezing rate. In our study, pig aortas were non-invasively scanned by micro-CT in each stage of freeze-drying at different pre-freezing rates, then comparing the porosity ratio and grey level under different conditions with each other to analysis the influence of different methods on the aorta. The mechanical properties of rehydrated pig aorta and fresh one were compared by texture profile analyzer to investigate the influence of different pre-freezing rates on mechanical properties in pig aorta. Our results showed that the proper pre-freezing rate for freeze-drying were 1 C/min. The changing rates of porosity rate and the average gray scale value were 16.6% and 3.64% respectively after freeze-dried. The puncture tolerance (PT) and circumferential tensile stress were increased about 20% and 30% respectively, and the axial tensile stress (ATS) were decreased about 20% in rehydrated aorta compared with fresh aorta. We otherwise conclude that under optimized process conditions, freeze-dried aorta with proper porosity rate and mechanical properties approximate fresh aorta could be preparation.
Topics: Animals; Aorta, Thoracic; Biomechanical Phenomena; Bioprosthesis; Blood Vessel Prosthesis; Freeze Drying; In Vitro Techniques; Porosity; Tensile Strength; Tissue Preservation; Vacuum; X-Ray Microtomography
PubMed: 22201762
DOI: 10.2741/3945 -
The Journal of Thoracic and... Nov 2021
Topics: Aorta, Thoracic; Humans
PubMed: 32171484
DOI: 10.1016/j.jtcvs.2020.02.061 -
European Journal of Vascular and... Apr 2018To compare porcine and human thoracic aortic stiffness using the available literature. (Comparative Study)
Comparative Study
OBJECTIVES
To compare porcine and human thoracic aortic stiffness using the available literature.
METHODS
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.
RESULTS
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 humans ≥60 years. In the descending aorta, circumferential and longitudinal stiffness were 0.46±0.03 MPa and 0.44±0.01 MPa for porcine aortas (4-10 months) versus 1.04±0.70 MPa and 1.24±0.76 MPa for humans <60 years, and 3.15±3.31 MPa and 1.17±0.31 MPa for humans ≥60 years.
CONCLUSIONS
The stiffness of young porcine aortic tissue shows good correspondence with human tissue aged <60 years, especially in the ascending aorta. Young porcine aortic tissue is less stiff than human aortic tissue aged ≥60 years.
Topics: Aging; Animals; Aorta, Thoracic; Humans; Models, Statistical; Swine; Vascular Stiffness
PubMed: 29402669
DOI: 10.1016/j.ejvs.2017.12.014 -
Medical Engineering & Physics Oct 2023Cardiovascular disease is widespread in girls and women living with Turner syndrome (TS). Despite this prevalence, cardiovascular risk evaluation using the current...
Cardiovascular disease is widespread in girls and women living with Turner syndrome (TS). Despite this prevalence, cardiovascular risk evaluation using the current guidelines has seen life-threatening aortic events occurring at dimensions classified within the normal threshold. In this study, we characterized the three-dimensional aortic geometries of Turner syndrome children and their age-matched healthy counterparts to evaluate various morphological parameters. Turner syndrome girls had overall greater values in ten out of fifteen parameters examined (p > 0.05), when compared to healthy children: the aortic arch height and width; the ascending aorta, aortic arch (2 locations), and descending aorta diameters; the ratio of the ascending to descending aorta diameter; average curvature; average torsion; and average curvature-torsion score. Additionally, significant associations were found in the TS group: body surface area and both arch height (p = 0.03) and arch height to width ratio (p = 0.05), and aortic arch diameter and both body surface area (p = 0.04) and weight (p = 0.04). The new information resulting from this small cohort study contributes to an improved understanding of the morphological parameters affecting the hemodynamic environment in TS, and the clinical assessment of the increased cardiovascular risk in this population.
Topics: Child; Humans; Female; Turner Syndrome; Cohort Studies; Magnetic Resonance Imaging; Aorta; Aorta, Thoracic
PubMed: 37838399
DOI: 10.1016/j.medengphy.2023.104045 -
Annals of Biomedical Engineering Apr 2023Thoracic aortic aneurysm (TAA) is characterized by dilation of the aorta that can lead to dissection or rupture. Degradation of elastic fibers is a consistent...
Thoracic aortic aneurysm (TAA) is characterized by dilation of the aorta that can lead to dissection or rupture. Degradation of elastic fibers is a consistent histopathological feature of TAA that likely contributes to disease progression. Pentagalloyl glucose (PGG) shows promise for stabilizing elastic fibers in abdominal aortic aneurysms, but its efficacy and mechanical effects in the thoracic aorta are unknown. We simulated TAAs using elastase (ELA) to degrade elastic fibers in the mouse ascending aorta and determined the preventative and restorative potential of PGG. Biaxial mechanical tests, constitutive model fitting, and multiphoton imaging were performed on untreated (UNT), PGG, ELA, PGG + ELA, and ELA + PGG treated aortas. PGG treatment alone does not significantly alter mechanical properties or wall structure compared to UNT. ELA treatment alone causes an increase in the unloaded diameter and length, decreased compliance, significant changes in the material constants, and separation of the outer layers of the aortic wall compared to UNT. PGG treatment before or after ELA ameliorates the mechanical and structural changes associated with elastic fiber degradation, with preventative PGG treatment being most effective. These results suggest that PGG is a potential pharmaceutical option to stabilize elastic fibers in TAA.
Topics: Mice; Animals; Elastic Tissue; Aorta; Aortic Aneurysm, Thoracic; Pancreatic Elastase; Pharmaceutical Preparations; Glucose
PubMed: 36203118
DOI: 10.1007/s10439-022-03093-x -
Journal of Visualized Experiments : JoVE Sep 2017The aorta is the largest artery in the body. The aortic wall is composed of an inner layer of endothelial cells, a middle layer of alternating elastic lamellae and...
The aorta is the largest artery in the body. The aortic wall is composed of an inner layer of endothelial cells, a middle layer of alternating elastic lamellae and smooth muscle cells (SMCs), and an outer layer of fibroblasts and extracellular matrix. In contrast to the widespread study of pathological models (e.g., atherosclerosis) in the adult aorta, much less is known about the embryonic and perinatal aorta. Here, we focus on SMCs and provide protocols for the analysis of the morphogenesis and pathogenesis of embryonic and perinatal aortic SMCs in normal development and disease. Specifically, the four protocols included are: i) in vivo embryonic fate mapping and clonal analysis; ii) explant embryonic aorta culture; iii) SMC isolation from the perinatal aorta; and iv) subcutaneous osmotic mini-pump placement in pregnant (or non-pregnant) mice. Thus, these approaches facilitate the investigation of the origin(s), fate, and clonal architecture of SMCs in the aorta in vivo. They allow for modulating embryonic aorta morphogenesis in utero by continuous exposure to pharmacological agents. In addition, isolated aortic tissue explants or aortic SMCs can be used to gain insights into the role of specific gene targets during fundamental processes such as muscularization, proliferation, and migration. These hypothesis-generating experiments on isolated SMCs and the explanted aorta can then be assessed in the in vivo context through pharmacological and genetic approaches.
Topics: Animals; Aorta; Cells, Cultured; Mice; Morphogenesis; Muscle, Smooth, Vascular
PubMed: 28930997
DOI: 10.3791/56039 -
American Journal of Physiology. Heart... Jul 2020Protection against increased vascular stiffness in young women is lost after menopause. However, little is known about vascular stiffness in older, premenopausal...
Protection against increased vascular stiffness in young women is lost after menopause. However, little is known about vascular stiffness in older, premenopausal females, because most of the prior work has been conducted in rodents, which live for only 1-3 yr and do not go through menopause. The goal of the current investigation was to quantitate differences in stiffness down the aortic tree and the mechanisms mediating those differences in older, premenopausal (24 ± 0.7 yr) versus young adult (7 ± 0.7 yr) female nonhuman primates. Aortic stiffness (β), calculated from direct and continuous measurements of aortic diameter and pressure in chronically instrumented, conscious macaque monkeys, increased 2.5-fold in the thoracic aorta and fivefold in the abdominal aorta in old premenopausal monkeys. The aortic histological mechanisms mediating increased vascular stiffness, i.e., collagen/elastin ratio, elastin, and collagen disarray, and the number of breaks in elastin and collagen fibers were greater in the old premenopausal versus young monkeys and greater in the abdominal versus the thoracic aorta and greatest in the iliac artery. In addition, more immature and less cross-linked fibers of collagen were found in the aortas of young females. Aortic stiffness increased in old premenopausal female monkeys, more so in the abdominal aorta than in the thoracic aorta. Histological mechanisms mediating the increased aortic stiffness were augmented in the old premenopausal females, greater in the abdominal versus the thoracic aorta, and greatest in the iliac artery. This is the first study to examine vascular stiffness down the aortic tree in aging premenopausal females (24 ± 0.7 yr old), whereas prior work studied mainly rodents, which are short-lived and do not undergo menopause. Histological mechanisms mediating vascular stiffness in older premenopausal females increased progressively down the aortic tree, with greater increases in the abdominal aorta compared with the thoracic aorta and with the greatest increases and differences observed in the iliac artery.
Topics: Aging; Animals; Aorta; Collagen; Elastin; Female; Macaca fascicularis; Macaca mulatta; Vascular Stiffness
PubMed: 32530752
DOI: 10.1152/ajpheart.00153.2020 -
Interactive Cardiovascular and Thoracic... Apr 2021Transcatheter aortic root repair (TARR) consists of the simultaneous endovascular replacement of the aortic valve, the root and the proximal ascending aorta. The aim of...
OBJECTIVES
Transcatheter aortic root repair (TARR) consists of the simultaneous endovascular replacement of the aortic valve, the root and the proximal ascending aorta. The aim of the study is to set-up a computational model of TARR to explore the impact of the endovascular procedure on the coronary circulation supported by chimney grafts.
METHODS
Computed tomography of a patient with dilated ascending aorta was segmented to obtain a 3-dimensional representation of the proximal thoracic aorta, including aortic root and supra-aortic branches. Computed assisted design tools were used to modify the geometry to create the post-procedural TARR configuration featuring the main aortic endograft integrated with 2 chimney grafts for coronary circulation. Computational Fluid Dynamics simulations were run in both pre- and post-procedural configurations using a pulsatile inflow and lumped parameter models at the outflows to simulate peripheral aortic and coronary circulation. Differences in coronary flow and pressure along the cardiac cycle were evaluated.
RESULTS
After the virtual implant of the TARR device with coronary grafts, the flow became more organized and less recirculation was seen in the ascending aorta. Coronary perfusion was guaranteed with negligible flow differences between pre- and post-procedural configurations. However, despite being well perfused by chimney grafts, the procedure induces an increase of the pressure drop between the coronary ostia and the ascending aorta of 8 mmHg.
CONCLUSIONS
The proposed numerical simulations, in the specific case under investigation, suggest that the TARR technique maintains coronary perfusion through the chimney grafts. This study calls for experimental validation and further analyses of the impact of TARR on cardiac afterload, decrease of aortic compliance and local pressure drop induced by the coronary chimney grafts.
Topics: Aorta; Blood Vessel Prosthesis; Computer Simulation; Coronary Circulation; Humans; Hydrodynamics; Imaging, Three-Dimensional; Pressure; Prosthesis Design; Tomography, X-Ray Computed; Transcatheter Aortic Valve Replacement
PubMed: 33351896
DOI: 10.1093/icvts/ivaa288 -
Annals of Biomedical Engineering Feb 2022Computational models of aortic dissection can examine mechanisms by which this potentially lethal condition develops and propagates. We present results from phase-field...
Computational models of aortic dissection can examine mechanisms by which this potentially lethal condition develops and propagates. We present results from phase-field finite element simulations that are motivated by a classical but seldom repeated experiment. Initial simulations agreed qualitatively and quantitatively with data, yet because of the complexity of the problem it was difficult to discern trends. Simplified analytical models were used to gain further insight. Together, simplified and phase-field models reveal power-law-based relationships between the pressure that initiates an intramural tear and key geometric and mechanical factors-insult surface area, wall stiffness, and tearing energy. The degree of axial stretch and luminal pressure similarly influence the pressure of tearing, which was ~88 kPa for healthy and diseased human aortas having sub-millimeter-sized initial insults, but lower for larger tear sizes. Finally, simulations show that the direction a tear propagates is influenced by focal regions of weakening or strengthening, which can drive the tear towards the lumen (dissection) or adventitia (rupture). Additional data on human aortas having different predisposing disease conditions will be needed to extend these results further, but the present findings show that physiologic pressures can propagate initial medial defects into delaminations that can serve as precursors to dissection.
Topics: Aortic Dissection; Aorta; Computer Simulation; Humans; Models, Cardiovascular; Pressure
PubMed: 35044571
DOI: 10.1007/s10439-022-02906-3