The present invention relates to a system and method for positioning a sheath and guiderail catheter into the Coronary Sinus (CS) to introduce pacing therapy within a heart of a subject. The guiderail catheter can be customized into a shape compatible with the subjects anatomy and also provide for shapeability of the guiderail catheter. The method includes introducing the sheath into the heart of the subject, with the sheath positioned in the right atrium. The guiderail catheter is introduced into the heart of the subject through the distal end of the sheath and advanced past the distal end of the sheath into the right atrium of the heart to a position near the septum and further guiding the distal end of the guiderail catheter into the coronary sinus.
