An impeller (605) includes a hub (610) and at least one blade (612) supported by the hub. The impeller has a stored configuration in which the blade is compressed so that its distal end moves towards the hub, and a deployed configuration in which the blade extends away from the hub. The impeller may be part of a pump for pumping fluids, such as pumping blood within a patient. A blood pump (600) may include a cannula (625) having a proximal portion (623) with a fixed diameter, and a distal portion (626) with an expandable diameter. The impeller may reside in the expandable portion of the cannula. The cannula may have a compressed diameter which allows it to be inserted percutaneously into a patient. Once at a desired location, the expandable portion of the cannula may be expanded and the impeller expanded to the deployed configuration. A flexible drive shaft (630) may extend through the cannula for rotationally driving the impeller within the patient's body.
