Dynamic characteristic modeling of left ventricular assist devices based on hysteresis effects.

The purpose of this study is to develop a new model for the dynamic characteristics of left ventricular assist devices (LVADs) interacting with the cardiovascular system under constant-speed modes. A new hysteresis model is established on the basis of the hysteresis effect and turbomachinery principles. The simulation results from the hysteresis model were compared with the inertia model. The in-vitro experiment results of a centrifugal pump (from literature) and the unsteady computational fluid dynamics (CFD) simulation results of an axial pump were used as the benchmarks. Compared with the inertia model, at the partial support mode, the relative estimation error of the time to the maximum and minimum pump flow (Q) in the hysteresis model decreased at least 16.3% cardiac cycle (Tc) in the centrifugal pump and at least 1.9% Tc in the axial pump, indicating its ability to simulate more realistic Q fluctuations. Moreover, the hysteresis model could predict an accurate time distribution of different Q. The hysteresis model provides a general calculation method for simulating the dynamic characteristics of constant-speed LVADs under interaction with the cardiovascular system. It is more accurate than the inertia model. The hysteresis model is helpful for the rapid estimation of unsteady dynamic characteristics in absence of a physical pump prototype at the preliminary design stage.