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An adolescent patient,in the peak of growth and development,with severe skeletal Class Ⅲ malocclusion and maxillary impacted canines was treated by removable and fixed appliances in the upper and lower dental arches.After treatment,the crossbite was relieved,the facial contour was improved,the integrity of the denture was kept and the Class Ⅰ molar relationship was achieved.
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Objective To study the two-phase flow dynamics distribution and red blood cell distribution under the fluid-solid coupling interaction in left coronary artery at the typical time point within one cardiac cycle,and to investigate the formation and development mechanisms of left coronary artery atherosclerotic plaque Methods The blood was regarded as a two-phase fluid.Based on fluid-solid interaction between blood and vascular wall,the computational fluid dynamics method was used to make the transient numerical simulation of two-phase flow in the left coronary artery under fluid-solid interaction;the distribution of blood flow in the left coronary artery at the typical time point within one cardiac cycle was studied,the relationship between hemodynamic parameters and the formation of atherosclerotic plaque was analyzed.Results A lowspeed eddy zone existed in an area between the distal segment of circumferential branch and the proximal outside of blunt-edge branch of the left coronary artery,where both internal wall shear stress and red blood cell volume fraction were very small and the blood flow pattern was very complicated.Conclusion At the lowspeed eddy zone that carries small wall shear stress,the lipid concentration polarization and macromolecular material deposition are easy to be produced.The area that has less red blood cells is liable to develop hypoxia,resulting in increased vascular wall permeability and intimal injury,which will activate the immune system,causing lipid accumulation in vascular wall and intimal hyperplasia and,thus,to induce the formation of atherosclerotic plaque.(J Intervent Radiol,2017,26:253-257)
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Pulse waves contain abundant physiological and pathological information of human body. Research of the relationship between pulse wave and human cardiovascular physiological parameters can not only help clinical diagnosis and treatment of cardiovascular diseases, but also contribute to develop many new medical instruments. Based on the traditional double elastic cavity model, the human cardiovascular system was established by using the electric network model in this paper. The change of wall pressure and blood flow in artery was simulated. And the influence of the peripheral resistance and vessel compliance to the distribution of blood flow in artery was analyzed. The simulation results were compared with the clinical monitoring results to predict the physiological and pathological state of human body. The result showed that the simulation waveform of arterial wall pressure and blood flow was stabile after the second cardiac cycle. With the increasing of peripheral resistance, the systolic blood pressure of artery increased, the diastolic blood pressure had no significant change, and the pulse pressure of artery increased gradually. With the decreasing of vessel compliance, the vasoactivity became worse and the pulse pressure increased correspondingly. The simulation results were consistent with the clinical monitoring results. The increasing of peripheral resistance and decreasing of vascular compliance indicated that the incidence of hypertension and atherosclerosis was increased.
Assuntos
Humanos , Aorta , Artérias , Fisiologia , Aterosclerose , Pressão Sanguínea , Doenças Cardiovasculares , Eletricidade , Coração , Fisiologia , Hemodinâmica , Hipertensão , Modelos Cardiovasculares , Resistência VascularRESUMO
Objective To study the distribution of hemodynamics in carotid artery under the fluid-solid interaction at the typical point of time during a single cardiac cycle, and to explore the mechanism of the formation and development of carotid atherosclerotic plaque. Methods Numerical analysis the blood flow characteristics within a cardiac cycle in carotid artery was analyzed by using computational method of fluid dynamics. Based on the hemodynamic parameters, the influences of the cardiac systole and diastole on the blood flow distribution were analyzed. Results The distribution of blood flow in the carotid artery within a typical cardiac cycle was obtained. Compared with the findings in cardiac diastole, a larger area of blood stasis at the entrance of external carotid artery was observed. In this area, the flow velocity, the wall pressure and the wall shear stress were all lower, while the arterial wall deformation and von Mises equivalent stress were larger. Conclusion Under fluid-solid interaction, the low blood flow in carotid artery causes blood reflux, resulting in the deposition of lipid, fiber and other large molecular materials. The low wall pressure produced“negative pressure” effect, thus the normal blood flow is changed, the flow velocity becomes slow, and the blood supply of the brain becomes insufficient. The low wall shear stress destroys the blood flow near the wall, causing the increase of platelet activity and intimal hyperplasia. The larger arterial wall deformation variable and von Mises equivalent stress can cause stress concentration and increase vascular rupture risk.