A multi-conductor cable for use in a catheter is described. The conductor-cable is isotropically flexible to allow catheter steering, but is also longitudinally stiff enough to push and pull the entire cable through the catheter lumen. In one implementation, the multi-conductor cable is bundled for most of its length, to provide longitudinal stiffness and support pushing and pulling the cable through a catheter lumen. However, in one such implementation, the portion of the cable within a steerable section of the catheter is unbundled and divided into individual conductors or groups that are flexible enough that they do not bias or otherwise interfere with the steering of the catheter. In one such approach, a spring wire or other stiffening element is added to the cable at that location to preserve or enhance longitudinal stiffness (tension and compression) of the cable through the unbundled flexible section.
