Patent ID: 8676350

Claim:
An implantable medical electrical lead comprising: a flexible insulative body having a proximal end and an opposite distal end, the body defining a longitudinal axis of the lead; a connector coupled to the proximal end of the lead body configured for operatively coupling the lead to an implantable pulse generator; a first conductor extending within the lead body from the connector toward the distal end of the lead body; a first electrode coupled to the body and to the first conductor; and a distal tip assembly coupled to the distal end of the lead body including: a shell having an outer wall defining a shell proximal end, an opposite shell distal end, and an internal cavity between the shell proximal and distal ends, the shell further including a helix guide member extending at least partially across the cavity at or near the shell distal end and defining an axial surface and a distal opening bounded by an inner wall defined by the helix guide member and the outer wall of the shell; a coupler rotatably disposed within the cavity including a proximal shaft portion and a distal shaft portion having a distal end, the coupler further including a distal rotation stop member protruding axially from the distal end of the distal shaft portion, the distal rotation stop member defining an axial surface parallel with the longitudinal axis of the lead and being sized to be received within the distal opening so that a portion of the coupler extends beyond the inner wall; a fixation helix fixedly coupled to the distal shaft portion of the coupler and including a distal portion extending at least partially through the distal opening of the shell, wherein the fixation helix and the helix guide member are configured so that the fixation helix slidably contacts a portion of the helix guide member so that rotation of the coupler and the fixation helix causes axial translation of the coupler and the fixation helix relative to the shell between fully retracted and fully extended positions, and wherein the distal rotation stop member is configured to abut the axial surface of the helix guide member in the fully extended position so as to delimit further rotation and axial extension of the coupler and the fixation helix.