Methods and devices for separating an implanted object, such as a pacemaker lead, from tissue surrounding such object in a patient's vasculature system. Specifically, the tissue separating device includes a handle, an elongate sheath and a circular cutting blade that may extend from the distal end of the sheath upon actuating the handle. The elongate sheath, particularly its distal end, includes a non-uniform wall thickness having one or more thicker portions in the outer sheath, particularly the outer cam member, and/or one or more thicker portions in an inner member disposed radially inward of the blade. Having an increased wall thickness for a portion of either or both of the outer cam member and circular inner member assists in shielding the vasculature from the blade during extension and guides the lead away from that portion of the inner cam member and towards the center of the lumen, thereby decreasing the likelihood that the cutting surface will cut the lead upon lead entry or upon contact the tissue upon blade extension.
