A blood pump is implantable within the vasculature, such as within the pulmonary artery. The pump may project through a native valve such as the pulmonary valve. In use, the pump opposes retrograde flow and thus acts as a replacement for the native valve. The pump may be an axial flow pump having a generally tubular housing adapted to fit within the space proximal to the bifurcation of the pulmonary artery while projecting only slightly proximally of the annulus of the native pulmonary valve.
