A device for promoting patency of a fistula includes an annular body and a plurality of vanes formed integrally with the annular body, and projecting inwardly from an inner radial surface thereof. The vanes are oriented so as to impart circumferential velocity components to blood passed through a lumen of the device, and such that an unobstructed line of sight parallel to a central axis of the annular body extends between adjacent ones of the vanes.
