An implantable lead conductor comprises at least one helical coil formed from at least one electrical cable. Each cable is formed from several wires twisted in a ropelike configuration with at least some of the wires being helically wound around a central axis of the cable. Each wire is a composite comprising a core of a first material and a coveting of a second material, with all adjacent wires belonging to the same cable in uninsulated contact with each other. Preferably, the core material is highly conductive, and the covering material is strong and biocompatible. The helical coil has a lumen for insertion of a stylet to facilitate insertion through a vein.