A method for modifying a pump of a ventricular assist device includes the step of modifying pressure-flow characteristics of a pump of a ventricular assist device to simulate different pressure-flow characteristics or to make the flow rate of the pump more responsive to changes in the pressure differential of the pump. The step of modifying the pressure-flow characteristics of the pump may includes one or both of the steps of (1) estimating a flow rate of the pump from the speed of an electric motor of the ventricular assist device and from the current or power consumption of the electric motor, wherein the electric motor drives the pump, and (2) adjusting the speed of the electric motor as a function of the estimated flow rate of the pump and a set speed of the electric motor to simulate the different pressure-flow characteristics or to make the flow rate of the pump more responsive to changes in the pressure differential of the pump.
