| The cardiovascular circulatory system is the basic systems of the human,the valve is the most important functional unit in the cardiovascular system.Due to the complexity of the valve anatomy,heart valve disease is a common disease in cardiovascular disease,such as mitral regurgitation,aortic valve calcification.Valve replacement surgery is effective to treat valve disease in clinical practice,that is,the artificial valve is implanted into the lesion to replace the natural valve.It plays an important role for valve replacement surgery to study hemodynamics with healthy and diseased heart valves.Based on the physiological characteristics of the cardiovascular system,the equivalent circuit model was used to simulate the cardiovascular dynamics with healthy and diseased valves.Firstly,the paper introduced the theoretical knowledge of the cardiovascular system,the anatomical structure and pathophysiology of the heart valve,the basic modeling methods and tools of physiological systems.Secondly,a leaflet motion resistance model was put forward for the mechanical valve,the model was used in the 0-D lumped parameter model of left heart circulation system and the results were discussed.Then valve orifice model with controllable closing volume was established,based on the characteristics of the biological native valve.Based on the model,the numerical model of the cardiovascular system was established and used with healthy and diseased heart valves,the simulation results agree well with results illustrated in cardiology textbooks.The research contents and innovations of the paper are as follows.1.This model had a variable resistance based on mitral valve leaflet opening angle θand involves the dynamic control equation of the mitral valve movement and main factors affecting the movement of the leaflets:transvalvular pressure and the blood flow force when it was applied in the 0-D lumped parameter model of left heart circulation system,the hemodynamics were derived.The results of this model,step-function model with instant valve closure and empirically specified time-varying resistance model were compared under the same cardiac output and regurgitation in left ventricular blood circulation.The leaflet motion resistance model reflects the hemodynamics of the closing process,such as the delayed blood flow behind pressure and closing volume,in addition,The model allows adjustment of the time required for valve opening and closing by changing the impact coefficients of moment of inertial of the leaflet,transvalvular pressure and blood flow-rate,the time of valve opening and closing are 50.0 ms and 40.2 ms in this paper.The model eliminates the shortcomings of ignoring leaflet motion of the step-function resistance model,as well as avoids use of the irrational starting time of valve closing in the time-varying resistance model.The model simulates the mitral valve dynamics accurately and is easy to be controlled.2.A valve orifice model with controllable closing volume was established in which the blood flow is divided into two parts: the flow through the valve orifice and the blood of pushing out by leaflet during the movement of the heart vale.The left heart circulatory simulation system was established using the valve model,the parameters of the valve were studied by Matlab and obtained the relationship between the closing volume,closing time and valve motion characteristics.Then the hemodynamics the left heart circulation system were simulated using the closing volume and closing time measured by the experiment.It is found that the simulation results are in agreement with the experimental results.3.A concentrated parameter model for the human cardiovascular system was established based on the valve model.The valve motion,pressure and heart valve blood flow were simulated in a healthy condition,the hemodynamic characteristics of the system were analyzed.Then,the hemodynamics of cardiovascular system were simulated with mitral regurgitation and aortic valve calcification by changing the parameters of vavle model,and compared with the results of healthy heart valves,the hemodynamic changes of diseased heart valves were analyzed.This research provides technical support in clinical pathology treatment for diseased heart valve. |
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