An electrode lead for implantation into a small heart vessel, especially into a coronary sinus, is provided with an elongated outer insulating lead body (1), having a proximal end (2), a distal end (3) and at least one electrode pole (4) at the distal end (3). At least one electrical conductor unit (6, 6') leads to said electrode pole (4), each of said electrical conductor units (6, 6') having a conductor core (7) and a separate insulating sheath (8) surrounding said conductor core (7). A lumen (9) is provided in said insulating lead body (1), being defined by a tubular envelope (10), to accommodate a guide wire means (11). The at least one electrical conductor unit (6, 6') and the envelope (10) of the lumen (9) are each slidable relative to each other along their longitudinal direction (L) and fixed relative to each other at least in the vicinity of the distal end (3) of the lead body (1).