Patent ID: 8233994

Claim:
A medical electrical lead comprising: an elongated body having a proximal end and a distal end; a helical fixation member extending from the distal end of the elongated body, the helical fixation member having a distal tip for fixedly engaging the distal end of the elongated body at an implant site, and a tracking member extending from the distal end of the elongated body and extending through the helical fixation member and outward from the distal tip of the helical fixation member, wherein the tracking member having a proximal portion extending out from the elongated body distal end having an outer diameter, and the helical fixation member having a corresponding proximal portion extending out from the elongated body distal end; and wherein the helical fixation member includes a first winding diameter along a proximal portion of the helical fixation member extending from the elongated body distal end and a second winding diameter, greater than the first winding diameter, along a distal portion of the helical fixation member, a tissue engaging gap extending along the second winding diameter of the distal portion of the helical fixation member, the helical fixation member proximal portion having the first winding diameter forming a mechanical stop for resisting further advancement of the helical fixation member into the tissue.