Reduced diameter active fixation pacing lead using concentric interleaved coils

A body implantable flexible lead assembly adapted to transmit electrical pulses between a proximal end of the lead assembly and a distal end of the assembly to stimulate selected body tissue, the assembly including:

• a tubular, insulating housing connecting the proximal and distal ends of the assembly and having a central longitudinal axis;
• a pair of coiled, insulated conductors extending between the proximal and distal ends of the assembly for transmitting electrical signals, the coils of the pair of insulated conductors having substantially the same diameter, portions of the pair of coiled conductors being interleaved, one of the coiled conductors being rotatable about the longitudinal axis relative to the other coiled conductor and having a proximal end and a distal end;
• and
• a helix electrode electrically connected to the distal end of the one coiled conductor for piercing the tissue to be stimulated, the one coiled conductor being adapted to extend or retract the helix electrode relative to the distal end of the assembly through rotation of the proximal end of the one coiled conductor.