Investigations into the Potential of Using Open Source CFD to Analyze the Differences in Hemodynamic Parameters for Aortic Dissections (Healthy versus Stanford Type A and B)
Ryo TakedaFumiya SatoH YokoyamaKatsuhiko SASAKINobuyuki OshimaAkiyoshi KurodaHideyoshi TakashimaChenyu LiShinya HondaHiroyuki Kamiya
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Pulsatile flow
Cardiac cycle
Lumen (anatomy)
The objective of this study is to investigate the hemodynamics in patient-specific internal carotid aneurysm and discuss the reason for rupture of aneurysm. A 3-Dimensional pulsatile blood flow in internal carotid with a sidewall aneurysm was studied numerically with the average Reynolds number of 704. Patient-specific model whose parent artery has a large "S" bending and a sidewall aneurysm was constructed from CT data. Unsteady, incompressible, 3-Dimensional Navier-Stokes equations were employed to solve the flow field. The temporal distributions of hemodynamic variables during the cardiac cycle such as streamlines, wall pressure and wall shear stress (WSS) in the arteries and aneurysm were analyzed. From streamlines it can be found that there is an obvious vortex flow in aneurismal cavity in a cardiac cycle. The type of this vortex flow is not changed in a cardiac cycle. As far as Wall Shear Stress, there is a region in aneurismal neck where the value of WSS is relatively high. Growth and rupture mechanism of internal carotid aneurysm in patient can be analyzed based on patient-specific model and hemodynamics simulation.
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Objective To explore the hemodynamic characteristics in an artery with asymmetric stenosis in a physiological pulsating state.Methods Based on animal experiment,the principle and method of fluid dynamics method was applied.The blood flow seemed to be an incompressible Bingham fluid,with a pulsating movement in arteries in a cardiac cycle.Navier-Stokes equation was the governing equation for blood flow,and was solved by finite element method(FEM).Results Some important hemodynamic factors such as flow field,velocity field,wall shear stress(WSS) distribution and the like were obtained in a cardiac cycle.Conclusion The geometrical factors may play the most important role in arterial hemodynamics,and the pulsatile character has the definite influence too.
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Aortic dissection is a severe pathological condition in which blood penetrates between layers of the aortic wall and creates a duplicate channel – the false lumen. This considerable change on the aortic morphology alters hemodynamic features dramatically and, in the case of rupture, induces markedly high rates of morbidity and mortality. In this study, we establish a patient-specific computational model and simulate the pulsatile blood flow within the dissected aorta. The k-ω SST turbulence model is employed to represent the flow and finite volume method is applied for numerical solutions. Our emphasis is on flow exchange between true and false lumen during the cardiac cycle and on quantifying the flow across specific passages. Loading distributions including pressure and wall shear stress have also been investigated and results of direct simulations are compared with solutions employing appropriate turbulence models. Our results indicate that (i) high velocities occur at the periphery of the entries; (ii) for the case studied, approximately 40% of the blood flow passes the false lumen during a heartbeat cycle; (iii) higher pressures are found at the outer wall of the dissection, which may induce further dilation of the pseudo-lumen; (iv) highest wall shear stresses occur around the entries, perhaps indicating the vulnerability of this region to further splitting; and (v) laminar simulations with adequately fine mesh resolutions, especially refined near the walls, can capture similar flow patterns to the (coarser mesh) turbulent results, although the absolute magnitudes computed are in general smaller. The patient-specific model of aortic dissection provides detailed flow information of blood transport within the true and false lumen and quantifies the loading distributions over the aorta and dissection walls. This contributes to evaluating potential thrombotic behavior in the false lumen and is pivotal in guiding endovascular intervention. Moreover, as a computational study, mesh requirements to successfully evaluate the hemodynamic parameters have been proposed.
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Lumen (anatomy)
Cardiac cycle
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Lumen (anatomy)
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To discuss the relationship between the development of thoracic aortic dissection(TVD) and hemodynamics,three-dimensional simulation of blood flow in human DeBakey Ⅲ type of TVD is investigated in normal and hypertension blood pressure using computational fluid dynamics.The pathline distributions on longitudinal section and cross-section of true and false lumens,wall pressure and wall shear stress for the blood flow of the TVD of DeBakey type Ⅲ are obtained in a cardiac cycle.Numerical results show that the hemodynamic behaviors are closely related to the blood pressure,while the blood pressure has slight influence on the shear stress distribution.The blood pressure in true lumen is also larger than that in false lumen in systole,which suggests that the lumen may expand along the origin lumen.
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Systole
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Abdominal aorta
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Abstract It is hypothesized that the beneficial effect of exercise in retarding the progression of cardiovascular disease is due, at least in part, to the elimination of adverse hemodynamic conditions including high particle residence time and low wall shear stress [1]. In-vitro and in-vivo investigations have provided limited qualitative information on flow patterns in the abdominal aorta and the effect of exercise on eliminating adverse hemodynamic conditions [2]. A computer model of a normal human abdominal aorta was created to simulate aortic blood flow under rest and graded exercise, pulsatile, flow conditions. Flow patterns, wall shear stress and particle residence time were computed in the lesion-prone infrarenal aorta and the effect of exercise determined.
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Abdominal aorta
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Arterial wall biomechanics are thought to be important in aneurysm development and atherosclerotic plaque localization. Vessel wall dilation occurs because of pulsatile blood flow during the cardiac cycle. Until recently, it was commonly assumed that this dilation occurred concentrically about the center of the lumen. However, dynamic MR, CT, and ultrasound imaging techniques have now shown that aortic wall motion undergoes unequal circumferential deformation during the cardiac cycle. This phenomenon has been observed in both humans and pigs [1, 2]. The purpose of our study was to determine whether variations in circumferential aortic wall dilation persist across mammalian species.
Cardiac cycle
Pulsatile flow
Dilation (metric space)
Lumen (anatomy)
Abdominal aorta
Biomechanics
Arterial wall
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The objective of this study is to investigate the hemodynamics in patient-specific thoracic aortic aneurysm and discuss the reason for formation of aortic plaque. A 3-Dimensional pulsatile blood flow in thoracic aorta with a fusiform aneurysm and 3 main branched vessels was studied numerically with the average Reynolds number of 1399 and the Womersley number of 19.2. Based on the clinical 2-Dimensional CT slice data, the patient-specific geometry model was constructed using medical image process software. Unsteady, incompressible, 3-Dimensional Navier-Stokes equations were employed to solve the flow field. The temporal distributions of hemodynamic variables during the cardiac cycle such as streamlines, wall shear stresses in the arteries and aneurysm were analyzed. Growth and rupture mechanisms of thoracic aortic aneurysm in the patient can be analyzed based on patient-specific model and hemodynamics simulation.
Pulsatile flow
Cardiac cycle
Thoracic aortic aneurysm
Thoracic aorta
Fusiform Aneurysm
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