Abstract: A lead for use with a pacemaker in a pacing system, the lead having at least one electrode placed at its distal tip and a helical fixation member at the lead distal tip for screwing the lead into a patient's heart wall. The helical member is composed of shape-memory metal and until use is encapsulated in a shrunken state with a diameter less than the diameter of the lead casing. The encapsulation material is preferably mannitol or a like material which dissolves when placed in the human heart. The shape-memory helix when released from the encapsulation material assumes an expanded diameter, greater than electrode diameter and preferably greater, so that when it is screwed into the heart wall, the helical coils are displaced radially away from the outer edge of the tip electrode. By this design, the damage to the heart tissue caused by the helix does not affect the heart wall immediately proximate to the tip electrode.