A catheter system (400, 450) for a catheter pump, comprising: an elongate catheter body having a distal portion including an expandable cannula having an inlet and an outlet, the expandable cannula having a delivery profile and an operational profile larger than the delivery profile; an impeller assembly disposed in the cannula and including an impeller shaft and an impeller body including one or more impeller blades, the impeller blade(s) drawing fluid into the cannula when rotated in the fluid; and a sheath assembly (404, 454) configured to be advanced through a vasculature of a patient while containing the cannula and the impeller assembly therein, to deliver the cannula to a target location within the vasculature where it is advanced distally out of the sheath assembly (404, 454), the sheath assembly (404, 454) comprising: a distal cannula retention zone disposed over the expandable cannula and the impeller assembly, the distal cannula retention zone having a first configuration adapted to retain the expandable cannula in the delivery profile and having a first resistance to separation, and an elongate proximal separation zone adjacent the distal cannula retention zone and disposed over the elongate catheter body, the proximal separation zone having a second resistance to a separation force, the second resistance being less than the first resistance, wherein upon advancing the cannula distally out of the sheath assembly (404, 454), the proximal separation zone is configured to separate, under the separation force, into a first portion and a second portion disposed across a gap, the gap enabling the elongate catheter body to pass between the first and second portions (472A, 472B) to enable removal of the sheath assembly (404, 454) from the elongate catheter body for operation of the impeller assembly. an elongate catheter body having a distal portion including an expandable cannula having an inlet and an outlet, the expandable cannula having a delivery profile and an operational profile larger than the delivery profile; an impeller assembly disposed in the cannula and including an impeller shaft and an impeller body including one or more impeller blades, the impeller blade(s) drawing fluid into the cannula when rotated in the fluid; and a sheath assembly (404, 454) configured to be advanced through a vasculature of a patient while containing the cannula and the impeller assembly therein, to deliver the cannula to a target location within the vasculature where it is advanced distally out of the sheath assembly (404, 454), the sheath assembly (404, 454) comprising: a distal cannula retention zone disposed over the expandable cannula and the impeller assembly, the distal cannula retention zone having a first configuration adapted to retain the expandable cannula in the delivery profile and having a first resistance to separation, and an elongate proximal separation zone adjacent the distal cannula retention zone and disposed over the elongate catheter body, the proximal separation zone having a second resistance to a separation force, the second resistance being less than the first resistance, wherein upon advancing the cannula distally out of the sheath assembly (404, 454), the proximal separation zone is configured to separate, under the separation force, into a first portion and a second portion disposed across a gap, the gap enabling the elongate catheter body to pass between the first and second portions (472A, 472B) to enable removal of the sheath assembly (404, 454) from the elongate catheter body for operation of the impeller assembly. a distal cannula retention zone disposed over the expandable cannula and the impeller assembly, the distal cannula retention zone having a first configuration adapted to retain the expandable cannula in the delivery profile and having a first resistance to separation, and an elongate proximal separation zone adjacent the distal cannula retention zone and disposed over the elongate catheter body, the proximal separation zone having a second resistance to a separation force, the second resistance being less than the first resistance, wherein upon advancing the cannula distally out of the sheath assembly (404, 454), the proximal separation zone is configured to separate, under the separation force, into a first portion and a second portion disposed across a gap, the gap enabling the elongate catheter body to pass between the first and second portions (472A, 472B) to enable removal of the sheath assembly (404, 454) from the elongate catheter body for operation of the impeller assembly.