Numerical And Experimental Studies On The Hemodynamic Effect Of Blood Pulsatility On Aorta Under The Ventricalar Assist Device Support

Heart failure is a common clinical syndrome. It’s also the end stage performanceof many cardiovascular diseases. Heart transplantation is the only effective way tocure this disease. However, due to the limitation of heart donation, high cost, hinderof patients’ health condition, it is hard to popularize the heart transplantationworldwide. Hence, the artificial heart becomes an important way to solve this problem.Artificial heart, which is also called ventricle assist device, indicates the artificialdevice can partially or totally replace the pump function of natural heart. The devicecan ensure the blood purfusion of tissues and organs. As an essential part of artificialheart, the blood pump can be divided into pulsatile flow and continuous flow pump.The first generation is pulsatile blood pump. Until now, it cannot be solved due to thehuge size and heavy noise. The second generation pump is becoming hot in presentresearches. The traditional operation mode of blood pump is the Bypass, which meansthe blood pump is parallel with the natural heart, transfer blood flow from the apex ofheart to the ascending aorta. The left ventricular and blood pump transfer the blood toaorta respectively. Intra-aorta pump, a innovation mode, is researched independentlyby our group. Different from the traditional operation mode, the pump is implantedinto the aorta root and in series with left ventrical, which means it adopts cascadeoperation mode.The blood pump may exert an influence on the original blood flow, especially thepulsatility of it. So, a hearted debate arises from scholar to scholar focusing onwhether the pulsatile or continuous flow generates the same influence on patients ornot. Scholars mainly aim at the two extreme situations: total assistance and noneassistance, but the conditions between the two situations are ignored. In addition,there has been no related research carried out about cascade operation. This paperresearches the blood pulsatility changing laws of the two operation modes by themeans of mathematics model, and discusses the hemodynamic influence on aorta bynumerical simulation and experimental research. Firstly, the lumped parameter modelis carried out to get the changing laws of pulsatile index such as PI, PPI, EEP andSHE. Then, the numerical simulation of fluid-solid coupling is conducted underdifferent blood pulsatility donditions. At last, the in vitro and animal experiments aredeveloped to have a further exploration of the blood pulsatility changing laws during ventricular assist device support.The result shows that the pulsatile index PI is negatively related to the bloodassist index (BAI). The relationship between PI and BAI in cascade and paralleloperation modes can be expresses by four times and tcubic polynomial respectively.Second, the numerical simulation result shows that lower pulsatility of blood flowreduces the flow variation in axial and flow rotation in radial. The average wall shearstress and pressure gradient are also positively related to BAI, which reach the normallevel before the blood pulsatility reduces to the lowest value. At last, it is found thatthe blood perfusion and ventricle unloading going higher with the increasement ofblood assist index, while the blood pulsatility going lower persistently. All in all, thisresearch gets the quantitative relationship between blood pulsatility and blood assistindex of the two operation modes.This paper also achieves the hemodynamicinfluences of blood pulsatility on aorta such as flow variation, rotation, distributary,wall shear stress and pressure gradient.This study originally finds the quantitative relationship between blood pulsatilityand blood assist index of cascade operation of ventrical assist device using themathematical model, which gives an analytical solution for detecting the pulsatileindex of the control system. This study also firstly achieves the hemodynamic effectsof various levels of blood pulsatility on aorta with the closed-loop method combinedwith mathematical model, numerical simulation and experimental study. Thenumerical result and experimental data possess important significance on thelong-term research about the interaction between artificial heart and human body.