Implantable electrode lead

An implantable electrode lead comprising:

• a lead body having a proximal end and a distal end;
• an implantable device;
• connecting means arranged at the proximal end of the lead body and mechanically and electrically connected to the implantable device;
• at least one electrode arranged at the distal end of said lead body to transmit an electrical signal between said implantable device and said electrode when implanted in a predetermined portion to perform one or both of transmission of electrical stimulation to body tissue and sensing of an electrical signal from the body tissue;
• said lead body comprising
• a conductive coil obtained by helically winding a plurality of conductive wires each formed with an insulating coating layer and having a diameter (d), each said conductive wire is formed of a first metal material having low electric resistivity and a second metal material having excellent corrosion resistance and mechanical characteristics to form a cladding, the conductive coil being a multi-filar structure having an outer surface and a coil pitch diameter (D), and
• a sheath made of a bio-compatible electrically insulating material covering the outer surface of said conductive coil, the sheath having an inner surface;
• and
• said lead body having an outer diameter of not more than 2 mm, said electrically insulating material of said sheath is formed of a soft material having a Shore hardness of less than 80A, said conductive coil has a spring index (D/d) greater than 7.8, and a clearance between the outer surface of the conductive coil and the inner surface of the sheath is not less than 50 μm to provide a number of times of flexure of more than 108.