[Effect of a delay mode of a ventricular assist device on hemodynamics of the cardiovascular system].

The implantation of biventricular assist device (BiVAD) is more challenging than that of left ventricular assist device for the interaction in the process of multiple input and output. Besides, ventricular assist device (VAD) often runs in constant speed (CS) mode in clinical use and thus BiVAD also faces the problems of low pulsation and imbalance of blood volume between systemic circulation and pulmonary circulation. In this paper, a delay assist mode for a VAD by shortening the support time of VAD was put forward. Then, the effect of the delay mode on cardiac output, pulsation and the function of the aortic valve was observed by numerical method and the rules of hemodynamics were revealed. The research showed that compared with VAD supported in CS mode, the VAD using delay mode in systolic and diastolic period proposed in this paper could meet the demand of cardiac output perfusion and restore the function of the arterial valves. The open ratio of aortic valve (AV) and pulmonary valve (PV) increased with the time set in delay mode, and the blood through the AV/PV helped to balance the left and the right cardiac volume. Besides, delay mode also improved the pulsation index of arterial blood flow, which is conducive to the recovery of the ventricular pulse function of patients.双心室辅助装置（BiVAD）因多输入输出过程的相互作用，其植入相比左心室辅助装置更具挑战性。同时，因心室辅助装置（VAD）在临床上常工作于定转速（CS）模式，BiVAD面临由此引起的系统搏动性低及体循环与肺循环血容量不平衡等问题。本文提出一种缩短VAD支持时间的延时辅助方案，应用数值方法观察延时模式对心输出量、血流搏动性以及动脉瓣生理状态的影响，揭示系统的血液动力学变化规律。研究表明：与CS模式相比，本文提出的辅助方案通过延时设置可满足收缩期和舒张期内的最低灌注量要求，并能使保持关闭的动脉瓣恢复正常功能。主动脉瓣（AV）和肺动脉瓣（PV）开放比例随延时增长而上升，且流经AV/PV的血流量有助于左、右心血容量的平衡。此外，延时模式还可以提高动脉血流的搏动指数，有助于患者心室搏动功能的恢复。.