The index of motor current amplitude has feasibility in control for continuous flow pumps and evaluation of left ventricular function.

The index of motor current amplitude (ICA) has feasibility in continuous-flow ventricular assist device control. It can demonstrate the safe range of pump speed, which exists between the starting point of total assistance (t-point) and the starting point of sucking (s-point). The objective of this study was to investigate how the ICA characteristic curve changes with each condition of contractility, preload, and afterload changes. We changed preload, afterload, and contractility of closed-mock circulation and plotted the change of the ICA value against pump speed. Then the shift of ICA characteristic curve against the change of each condition was considered. When preload increased, ICA characteristic curves showed the expansion of a safe range. When afterload increased, ICA characteristic curves were shifted to the high rotation side, slightly narrowing a safe range. When contractility increased, ICA characteristic curves showed the shift of a convex above to narrowing of a safe range. As these shift patterns were observed even when the driving conditions of a circuit changed, reproducibility was checked. Understanding the feature of a shift pattern of ICA characteristic curves correctly, a possibility that change of the heart function could be predicted by change of ICA value and a possibility for a flexible control method based on ICA, according to hemodynamic state, were suggested.