Apparatus and methods are described for use with a venous system of a subject that includes one or more tributary vessels that flow into a vein at junctions. A blood-pump-catheter (70) includes a material (36) configured to be placed at a downstream location that is downstream of the junctions and to at least partially occlude blood flow through the vein. The material defines a blood-outlet opening (31). A blood pump (24) pumps blood from a region of the vein that is adjacent to the junctions, and through the blood-outlet opening (31). A blood-flow pathway (60) directs upstream venous blood flow from an upstream location that is upstream of the junctions, to downstream of the material (36), without the upstream venous blood flow being pumped by the pump (24). Other applications are also described.