Mechanical control of circulatory assist devices

Mechanical circulatory assist devices are grouped in two major classes depending on the manner in which they supply the pumping action: pulsatile or non-pulsatile. Electrohydraulic ventricular assist devices (EVADs) are inherently pulsatile. There is a tendency, in the design of such devices, to create an alternating non, by incorporating the alternation into the control system. This can create a reliability problem as it often requires that a mechanical component be made to reverse direction repetitively. One method to resolve this problem employs a rotary control valve constructed in a manner such that a pulsatile now is created in spite of a constant angular speed. The rotary valve is driven by the same electric motor used to drive the axial non pump that propels the working fluid.