In one aspect, an implantable pump system for assisting blood flow in a patient includes a blood flow path comprising a flexible conduit, at least one valve in fluid connection with the flexible conduit, a drive system in operative connection with the valve to move the valve in a reciprocating manner, an implantable control system and at least one sensor in communicative connection with the control system. The sensor is adapted to measure at least one property of blood. The control system is adapted to control movement of the valve on the basis of data regarding position of the valve with respect to time or a derivative thereof (that is, position, velocity, acceleration or a derivative thereof) in combination with data of the measured at least one property of blood from the sensor.