A loop assembly for a catheter, the assembly including a primary frame member, a secondary frame member, and a sleeve disposed around least one of the primary and secondary frame members. The primary frame member can have at least a first cross-sectional area and can include a pair of proximal ends extending along a longitudinal axis to a closed distal end. The secondary frame member can have at least a second cross-sectional area different from the first cross-sectional area, can be disposed on at least a portion of the primary frame member between the proximal ends and the closed distal end, and can be configured to slide in at least a first dimension relative to the primary frame member.