A rotary blood pump (10) comprising a housing defining a pumping chamber (3) with upper and lower interior surfaces and having a blood inlet (7) and a tangential blood outlet (13), and a rotatable impeller (22) within the pumping chamber (3) and adapted to increase blood pressure within the pumping chamber (3) to cause blood to move to the blood outlet (13), the impeller (22) having at least one raised surface area adjacent the upper interior surface of the pumping chamber (3). The rotary blood pump further comprises a first tapered region (34) of the raised surface area having a leading portion (36) and a trailing portion (37) and a gap between the first tapered region (34) and the upper interior surface of the housing decreases from the leading portion (36) to the trailing portion (37) creating a hydrodynamic thrust load acting to bias the impeller (22) axially away from the upper interior surface of the housing when the impeller (22) is rotating, each of the first tapered regions having a shroud (43, 44) extending from the leading portion to the trailing portion along each of its inner (43) and outer (44) boundaries.
