An elongated guide sheath for delivering at least one medical instrument to a body lumen. For reliable and cost effective implantation of an electrode at the AV septum the inventive guide sheath forms a first guiding sleeve and a second guiding sleeve at least partly separated by a shared wall section, wherein the longitudinal axis of the first guiding sleeve and the longitudinal axis of the second guiding sleeve run parallel to a longitudinal guide sheath axis, wherein the wall of the first guiding sleeve and/or of the second guiding sleeve each comprises a slit which runs along at least part of the length of the respective guiding sleeve. Further, a system including the above guide sheath, a first catheter and/or guide wire and a second catheter or electrode is proposed.
