The Experts below are selected from a list of 3453 Experts worldwide ranked by ideXlab platform
Kunihiko Tanaka - One of the best experts on this subject based on the ideXlab platform.
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relationship between Transmural Pressure and aortic diameter during free drop induced microgravity in anesthetized rats
Japanese Journal of Physiology, 2003Co-Authors: Hironobu Morita, Nobuhiro Fujiki, Taro M Gotoh, Tomoko Matsuda, Gao Shuang, Kunihiko TanakaAbstract:To test the hypothesis that the aortic wall is stretched without increasing aortic Pressure (AP) during microgravity (microG), the AP, intrathoracic Pressure (ITP), and aortic diameter (AD) were measured in anesthetized Sprague-Dawley rats during 4.5 s of microG produced by freefall. A smooth and immediate reduction in gravity (G) occurred during freefall, microG being achieved 100 ms after the start of the drop. Acute microG elicited an immediate increase in AD, which was not accompanied by an increase in AP. However, the ITP decreased during microG resulted in an increase in the calculated Transmural Pressure (TP = AP-ITP) of the aortic wall. A simple linear regression analysis showed that the slopes of the plot of AP vs. AD differed at 1 G and microG, whereas those for the plot of TP vs. AD did not. Thus, the increase in AD during microG was accounted for by the increase in TP. These results suggest that a decrease in ITP, resulting in an increase in TP of the aorta, is a key issue in understanding cardiovascular responses to microG.
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acute response of aortic nerve activity to free drop induced microgravity in anesthetized rats
Neuroscience Letters, 2001Co-Authors: Hironobu Morita, You Tsuchiya, Taro Miyahara, Kunihiko Tanaka, Nobuhiro FujikiAbstract:To test the hypothesis that arterial baroreflex was stimulated during microgravity (μG), arterial Pressure (AP), intrathoracic Pressure (ITP), and aortic nerve activity (ANA) were measured in anesthetized rats during 4.5 s of μG produced by free drop. A smooth and immediate reduction in G occurred during free drop, μG being achieved 100 ms after the start of the drop. Acute μG elicited an immediate and striking, but transient, increase in ANA, with no significant change in the AP, but a significant decrease in the end-expiratory ITP. The calculated Transmural Pressure of the aorta increased by 6.9 mmHg 2 s after the start of the drop. The increase in ANA lasted 2 s, then ANA returned to the control level, despite the calculated end-expiratory Transmural Pressure still being high. These results suggest that μG conditions stimulate the aortic baroreceptor by increasing Transmural Pressure by reducing the ITP. However, this effect is only transient, probably due to the high-pass property of the baroreceptors.
David A. Vorp - One of the best experts on this subject based on the ideXlab platform.
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Computer modeling for the prediction of thoracic aortic stent graft collapse.
2018Co-Authors: Salvatore Pasta, Jae-sung Cho, Onur Dur, Kerem Pekkan, David A. VorpAbstract:OBJECTIVE: To assess the biomechanical implications of excessive stent protrusion into the aortic arch in relation to thoracic aortic stent graft (TASG) collapse by simulating the structural load and quantifying the fluid dynamics on the TASG wall protrusion extended into a model arch. METHODS: One-way coupled fluid-solid interaction analyses were performed to investigate the flow-induced hemodynamic and structural loads exerted on the proximal protrusion of the TASG and aortic wall reconstructed from a patient who underwent traumatic thoracic aortic injury repair. Mechanical properties of a Gore TAG thoracic endoprosthesis (W. L. Gore and Assoc, Flagstaff, Ariz) were assessed via experimental radial compression testing and incorporated into the computational modeling. The TASG wall protrusion geometry was characterized by the protrusion extension (PE) and by the angle (θ) between the TASG and the lesser curvature of the aorta. The effect of θ was explored with the following four models with PE fixed at 1.1 cm: θ = 10 degrees, 20 degrees, 30 degrees, and 40 degrees. The effect of PE was evaluated with the following four models with θ fixed at 10 degrees: PE = 1.1 cm, 1.4 cm, 1.7 cm and 2.0 cm. RESULTS: The presence of TASG wall protrusion into the aortic arch resulted in the formation of swirling, complex flow regions in the proximal luminal surface of the endograft. High PE values (PE = 2.0 cm) led to a markedly reduced left subclavian flow rate (0.27 L/min), low systolic perfusion Pressure (98 mm Hg), and peak systolic TASG diameter reduction (2 mm). The Transmural Pressure load across the TASG was maximum for the model with the highest PE and θ, 15.2 mm Hg for the model with PE = 2.0 cm and θ = 10 degrees, and 11.6 mm Hg for PE = 1.1 cm and θ = 40 degrees. CONCLUSIONS: The findings of this study suggest that increased PE imparts an apparent risk of distal end-organ malperfusion and proximal hypertension and that both increased PE and θ lead to a markedly increased Transmural Pressure across the TASG wall, a load that would portend TASG collapse. Patient-specific computational modeling may allow for identification of patients with high risk of TASG collapse and guide preventive intervention. CLINICAL RELEVANCE: A potentially devastating complication that may occur after endovascular repair of traumatic thoracicaortic injuries is stent graft collapse. Although usually asymptomatic, stent graft collapse may be accompanied by adverse hemodynamic consequences. Numerous anatomic and device-related factors contribute to the development of collapse, but predictive factors have not yet been clearly defined. In the present study, we assessed the relevant hemodynamics and solid mechanics underlying stent graft collapse using a computational fluid-structure interaction framework of stent graft malapposition. Our findings suggest that both increased stent graft angle and extension into the aortic arch lead to a markedly increased Transmural Pressure across the stent graft wall, portending collapse. Patient-specific computational modeling may allow for identification of patients at high risk for collapse and aid in planning for an additional, prophylactic intervention to avert its occurrence.
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computer modeling for the prediction of thoracic aortic stent graft collapse
Journal of Vascular Surgery, 2011Co-Authors: Salvatore Pasta, Jae-sung Cho, Onur Dur, Kerem Pekkan, David A. VorpAbstract:Objective To assess the biomechanical implications of excessive stent protrusion into the aortic arch in relation to thoracic aortic stent graft (TASG) collapse by simulating the structural load and quantifying the fluid dynamics on the TASG wall protrusion extended into a model arch. Methods One-way coupled fluid-solid interaction analyses were performed to investigate the flow-induced hemodynamic and structural loads exerted on the proximal protrusion of the TASG and aortic wall reconstructed from a patient who underwent traumatic thoracic aortic injury repair. Mechanical properties of a Gore TAG thoracic endoprosthesis (W. L. Gore and Assoc, Flagstaff, Ariz) were assessed via experimental radial compression testing and incorporated into the computational modeling. The TASG wall protrusion geometry was characterized by the protrusion extension (PE) and by the angle (θ) between the TASG and the lesser curvature of the aorta. The effect of θ was explored with the following four models with PE fixed at 1.1 cm: θ = 10 degrees, 20 degrees, 30 degrees, and 40 degrees. The effect of PE was evaluated with the following four models with θ fixed at 10 degrees: PE = 1.1 cm, 1.4 cm, 1.7 cm and 2.0 cm. Results The presence of TASG wall protrusion into the aortic arch resulted in the formation of swirling, complex flow regions in the proximal luminal surface of the endograft. High PE values (PE = 2.0 cm) led to a markedly reduced left subclavian flow rate (0.27 L/min), low systolic perfusion Pressure (98 mm Hg), and peak systolic TASG diameter reduction (2 mm). The Transmural Pressure load across the TASG was maximum for the model with the highest PE and θ, 15.2 mm Hg for the model with PE = 2.0 cm and θ = 10 degrees, and 11.6 mm Hg for PE = 1.1 cm and θ = 40 degrees. Conclusions The findings of this study suggest that increased PE imparts an apparent risk of distal end-organ malperfusion and proximal hypertension and that both increased PE and θ lead to a markedly increased Transmural Pressure across the TASG wall, a load that would portend TASG collapse. Patient-specific computational modeling may allow for identification of patients with high risk of TASG collapse and guide preventive intervention.
Nobuhiro Fujiki - One of the best experts on this subject based on the ideXlab platform.
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relationship between Transmural Pressure and aortic diameter during free drop induced microgravity in anesthetized rats
Japanese Journal of Physiology, 2003Co-Authors: Hironobu Morita, Nobuhiro Fujiki, Taro M Gotoh, Tomoko Matsuda, Gao Shuang, Kunihiko TanakaAbstract:To test the hypothesis that the aortic wall is stretched without increasing aortic Pressure (AP) during microgravity (microG), the AP, intrathoracic Pressure (ITP), and aortic diameter (AD) were measured in anesthetized Sprague-Dawley rats during 4.5 s of microG produced by freefall. A smooth and immediate reduction in gravity (G) occurred during freefall, microG being achieved 100 ms after the start of the drop. Acute microG elicited an immediate increase in AD, which was not accompanied by an increase in AP. However, the ITP decreased during microG resulted in an increase in the calculated Transmural Pressure (TP = AP-ITP) of the aortic wall. A simple linear regression analysis showed that the slopes of the plot of AP vs. AD differed at 1 G and microG, whereas those for the plot of TP vs. AD did not. Thus, the increase in AD during microG was accounted for by the increase in TP. These results suggest that a decrease in ITP, resulting in an increase in TP of the aorta, is a key issue in understanding cardiovascular responses to microG.
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acute response of aortic nerve activity to free drop induced microgravity in anesthetized rats
Neuroscience Letters, 2001Co-Authors: Hironobu Morita, You Tsuchiya, Taro Miyahara, Kunihiko Tanaka, Nobuhiro FujikiAbstract:To test the hypothesis that arterial baroreflex was stimulated during microgravity (μG), arterial Pressure (AP), intrathoracic Pressure (ITP), and aortic nerve activity (ANA) were measured in anesthetized rats during 4.5 s of μG produced by free drop. A smooth and immediate reduction in G occurred during free drop, μG being achieved 100 ms after the start of the drop. Acute μG elicited an immediate and striking, but transient, increase in ANA, with no significant change in the AP, but a significant decrease in the end-expiratory ITP. The calculated Transmural Pressure of the aorta increased by 6.9 mmHg 2 s after the start of the drop. The increase in ANA lasted 2 s, then ANA returned to the control level, despite the calculated end-expiratory Transmural Pressure still being high. These results suggest that μG conditions stimulate the aortic baroreceptor by increasing Transmural Pressure by reducing the ITP. However, this effect is only transient, probably due to the high-pass property of the baroreceptors.
Hironobu Morita - One of the best experts on this subject based on the ideXlab platform.
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relationship between Transmural Pressure and aortic diameter during free drop induced microgravity in anesthetized rats
Japanese Journal of Physiology, 2003Co-Authors: Hironobu Morita, Nobuhiro Fujiki, Taro M Gotoh, Tomoko Matsuda, Gao Shuang, Kunihiko TanakaAbstract:To test the hypothesis that the aortic wall is stretched without increasing aortic Pressure (AP) during microgravity (microG), the AP, intrathoracic Pressure (ITP), and aortic diameter (AD) were measured in anesthetized Sprague-Dawley rats during 4.5 s of microG produced by freefall. A smooth and immediate reduction in gravity (G) occurred during freefall, microG being achieved 100 ms after the start of the drop. Acute microG elicited an immediate increase in AD, which was not accompanied by an increase in AP. However, the ITP decreased during microG resulted in an increase in the calculated Transmural Pressure (TP = AP-ITP) of the aortic wall. A simple linear regression analysis showed that the slopes of the plot of AP vs. AD differed at 1 G and microG, whereas those for the plot of TP vs. AD did not. Thus, the increase in AD during microG was accounted for by the increase in TP. These results suggest that a decrease in ITP, resulting in an increase in TP of the aorta, is a key issue in understanding cardiovascular responses to microG.
-
acute response of aortic nerve activity to free drop induced microgravity in anesthetized rats
Neuroscience Letters, 2001Co-Authors: Hironobu Morita, You Tsuchiya, Taro Miyahara, Kunihiko Tanaka, Nobuhiro FujikiAbstract:To test the hypothesis that arterial baroreflex was stimulated during microgravity (μG), arterial Pressure (AP), intrathoracic Pressure (ITP), and aortic nerve activity (ANA) were measured in anesthetized rats during 4.5 s of μG produced by free drop. A smooth and immediate reduction in G occurred during free drop, μG being achieved 100 ms after the start of the drop. Acute μG elicited an immediate and striking, but transient, increase in ANA, with no significant change in the AP, but a significant decrease in the end-expiratory ITP. The calculated Transmural Pressure of the aorta increased by 6.9 mmHg 2 s after the start of the drop. The increase in ANA lasted 2 s, then ANA returned to the control level, despite the calculated end-expiratory Transmural Pressure still being high. These results suggest that μG conditions stimulate the aortic baroreceptor by increasing Transmural Pressure by reducing the ITP. However, this effect is only transient, probably due to the high-pass property of the baroreceptors.
Kerem Pekkan - One of the best experts on this subject based on the ideXlab platform.
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Computer modeling for the prediction of thoracic aortic stent graft collapse.
2018Co-Authors: Salvatore Pasta, Jae-sung Cho, Onur Dur, Kerem Pekkan, David A. VorpAbstract:OBJECTIVE: To assess the biomechanical implications of excessive stent protrusion into the aortic arch in relation to thoracic aortic stent graft (TASG) collapse by simulating the structural load and quantifying the fluid dynamics on the TASG wall protrusion extended into a model arch. METHODS: One-way coupled fluid-solid interaction analyses were performed to investigate the flow-induced hemodynamic and structural loads exerted on the proximal protrusion of the TASG and aortic wall reconstructed from a patient who underwent traumatic thoracic aortic injury repair. Mechanical properties of a Gore TAG thoracic endoprosthesis (W. L. Gore and Assoc, Flagstaff, Ariz) were assessed via experimental radial compression testing and incorporated into the computational modeling. The TASG wall protrusion geometry was characterized by the protrusion extension (PE) and by the angle (θ) between the TASG and the lesser curvature of the aorta. The effect of θ was explored with the following four models with PE fixed at 1.1 cm: θ = 10 degrees, 20 degrees, 30 degrees, and 40 degrees. The effect of PE was evaluated with the following four models with θ fixed at 10 degrees: PE = 1.1 cm, 1.4 cm, 1.7 cm and 2.0 cm. RESULTS: The presence of TASG wall protrusion into the aortic arch resulted in the formation of swirling, complex flow regions in the proximal luminal surface of the endograft. High PE values (PE = 2.0 cm) led to a markedly reduced left subclavian flow rate (0.27 L/min), low systolic perfusion Pressure (98 mm Hg), and peak systolic TASG diameter reduction (2 mm). The Transmural Pressure load across the TASG was maximum for the model with the highest PE and θ, 15.2 mm Hg for the model with PE = 2.0 cm and θ = 10 degrees, and 11.6 mm Hg for PE = 1.1 cm and θ = 40 degrees. CONCLUSIONS: The findings of this study suggest that increased PE imparts an apparent risk of distal end-organ malperfusion and proximal hypertension and that both increased PE and θ lead to a markedly increased Transmural Pressure across the TASG wall, a load that would portend TASG collapse. Patient-specific computational modeling may allow for identification of patients with high risk of TASG collapse and guide preventive intervention. CLINICAL RELEVANCE: A potentially devastating complication that may occur after endovascular repair of traumatic thoracicaortic injuries is stent graft collapse. Although usually asymptomatic, stent graft collapse may be accompanied by adverse hemodynamic consequences. Numerous anatomic and device-related factors contribute to the development of collapse, but predictive factors have not yet been clearly defined. In the present study, we assessed the relevant hemodynamics and solid mechanics underlying stent graft collapse using a computational fluid-structure interaction framework of stent graft malapposition. Our findings suggest that both increased stent graft angle and extension into the aortic arch lead to a markedly increased Transmural Pressure across the stent graft wall, portending collapse. Patient-specific computational modeling may allow for identification of patients at high risk for collapse and aid in planning for an additional, prophylactic intervention to avert its occurrence.
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computer modeling for the prediction of thoracic aortic stent graft collapse
Journal of Vascular Surgery, 2011Co-Authors: Salvatore Pasta, Jae-sung Cho, Onur Dur, Kerem Pekkan, David A. VorpAbstract:Objective To assess the biomechanical implications of excessive stent protrusion into the aortic arch in relation to thoracic aortic stent graft (TASG) collapse by simulating the structural load and quantifying the fluid dynamics on the TASG wall protrusion extended into a model arch. Methods One-way coupled fluid-solid interaction analyses were performed to investigate the flow-induced hemodynamic and structural loads exerted on the proximal protrusion of the TASG and aortic wall reconstructed from a patient who underwent traumatic thoracic aortic injury repair. Mechanical properties of a Gore TAG thoracic endoprosthesis (W. L. Gore and Assoc, Flagstaff, Ariz) were assessed via experimental radial compression testing and incorporated into the computational modeling. The TASG wall protrusion geometry was characterized by the protrusion extension (PE) and by the angle (θ) between the TASG and the lesser curvature of the aorta. The effect of θ was explored with the following four models with PE fixed at 1.1 cm: θ = 10 degrees, 20 degrees, 30 degrees, and 40 degrees. The effect of PE was evaluated with the following four models with θ fixed at 10 degrees: PE = 1.1 cm, 1.4 cm, 1.7 cm and 2.0 cm. Results The presence of TASG wall protrusion into the aortic arch resulted in the formation of swirling, complex flow regions in the proximal luminal surface of the endograft. High PE values (PE = 2.0 cm) led to a markedly reduced left subclavian flow rate (0.27 L/min), low systolic perfusion Pressure (98 mm Hg), and peak systolic TASG diameter reduction (2 mm). The Transmural Pressure load across the TASG was maximum for the model with the highest PE and θ, 15.2 mm Hg for the model with PE = 2.0 cm and θ = 10 degrees, and 11.6 mm Hg for PE = 1.1 cm and θ = 40 degrees. Conclusions The findings of this study suggest that increased PE imparts an apparent risk of distal end-organ malperfusion and proximal hypertension and that both increased PE and θ lead to a markedly increased Transmural Pressure across the TASG wall, a load that would portend TASG collapse. Patient-specific computational modeling may allow for identification of patients with high risk of TASG collapse and guide preventive intervention.
