Design Of A New Direct Assist Blood Pump Based On Mechanical Analysis

A direct-assist blood pump is a pump that does not contact with blood directly and wraps around the outside of the heart to pump blood like a surgeon’s hand.It can significantly reduce the risk of complications,such as hemolysis,bleeding and embolism,caused by damage to blood cells,compared to a rotary blood pump.Moreover,long-term use of it helps to reduce myocardial fibrosis and decrease the probability of ventricular remodeling,thus helping restore the normal physiological function of the failing heart gradually.This article refers to the principles of biomimetic design,taking into account the distribution of myocardial fiber arrangement and the natural contraction of the heart,and proposes an efficient assist strategy that combines pressure application to the main and secondary assist areas.Then,a new direct-assist blood pump is designed,and the assist effect of the blood pump is verified through mechanic simulation analysis and hydraulic experiments.The main research contents are as follows.The material parameters of the heart are determined using constitutive and hyperelastic models,and a finite element model of the heart has been developed.Firstly,the H-O constitutive model is chosen to describe the mechanical properties of cardiac anisotropy,incompressibility,and large deformations based on mechanical knowledge.A hyperelastic model is used for the solution of the large deformation character of the heart.Then,the H-O constitutive model and the hyperelastic model are decoupled respectively and fitted to acquire the initial parameters of each part of the heart.Finally,according to the distribution of myocardial fibers and the structure of the heart,parameters are assigned to a certain part of heart to establish a global anisotropy cardiac finite element model.The finite element model of the heart is used to study the efficiency assist strategy.Firstly,the mechanical properties of the heart are analyzed by applying the conventional assist strategy of the direct-assist pump that squeezes the whole heart.Based on the analysis of stress-strain relations and MSE decision equations,this study proposes an efficiency assist strategy applying pressure in a combination of primary and secondary assist regions.Furthermore,numerical research is conducted on the efficient assist strategy,and stress distribution cloud maps and efficiency evaluation equation are used to assess the effectiveness and rationality of the strategy.Simulation is conducted to analyze the performance of this direct-assist blood pump using the efficient assist strategy,and the device is optimized based on the numerical results.Firstly,use the finite element model to evaluate the effects of different assist strategies on the assist efficiency of the blood pump and the ventricular physiological status.Secondly,based on the simulation results,a direct-assist blood pump design scheme using the efficient assist strategy is proposed and verified its effectiveness and feasibility.Finally,a prototype of the direct-assist heart pump is fabricated,and an optimized scheme is proposed as a control group to investigate the effect of the shape of the flexible support bars on the performance and efficiency of the direct-assist heart pump.Develops an experimental platform to carry out the hydraulic experiments of the direct-assist blood pump.The experiments include a static hydraulic experiment to verify the feasibility of the assist strategy and a dynamic hydraulic experiment to evaluate the performance of the blood pump.The results show that the direct-assist heart pump with an efficient assist strategy can effectively increase the cardiac output and pressure per beat,and enhance ventricular contraction function.Furthermore,it has been noted that taking into account the arrangement of myocardial fibers in the optimization design approach can contribute to enhancing the efficiency of the assistance strategy.