Apparatus and methods are described including a blood pump that includes an axial shaft configured for insertion, over a guidewire, into a subject's body, and for rotation within the subject's body. The axial shaft is shaped to define a shaft lumen for passage of the guidewire therethrough. An impeller is coupled to the axial shaft such that, as the axial shaft rotates, the impeller pumps blood of the subject. A thrust bearing is disposed distally from the axial shaft so as to inhibit distal movement of the axial shaft beyond the thrust bearing. The thrust bearing is shaped to define a bearing lumen that is configured to be continuous with the shaft lumen. At least a portion of the bearing lumen is frustoconically-shaped, a wider end of the frustoconically-shaped portion of the bearing lumen facing distally. Other applications are also described.