An introducer system (10) is used for implantation of pacemaker leads into the venous system of the human heart through the coronary sinus. The system is comprised of three telescopic components, an inner telescoping core (12), a precurved inner telescoping sheath (14), and an outer telescoping sheath (16), introducer, guide or catheter (10). A core (12) is used it is torsionally stiff. In an embodiment where no core is used, the inner sheath (14) is torsionally stiff. In either case, the member which is torsionally stiff is torqueable. In general, the inner sheath (14) and outer guide (16) will be both laterally and torsionally flexible, while the core (12) will be torsionally stiff. The core (12) and the inner sheath (14), when curved together in the venous system and proximally coupled will be sufficiently bound to each other that proximal rotation of the core will be coupled to and cause distal rotation of the inner sheath (14).