Abstract: In some variations, a circulatory assist system may include a pump body comprising a conduit having an inflow region and an outflow region, and a volume displacement member arranged in the conduit and operable between an expansion phase and a contraction phase. The circulatory assist system may also include an inlet valve arranged in the inflow region and comprising a plurality of leaflets. The inlet valve may receive blood into the conduit and the pump body may convey the received blood through the outflow region via cyclical operation of the volume displacement member between the expansion phase and the contraction phase. In some variations, the inlet valve may operate between open and closed states at high frequencies while withstanding a high pressure differential when the circulatory assist system is in use.