Active fixation lead with helix securement mechanism

An implantable lead comprising:

• a flexible body extending between a proximal end and a distal end;
• a connector assembly secured to the proximal end for coupling the lead to an implantable medical device, the connector assembly including a terminal pin rotatable relative to the body;
• a conductor member disposed longitudinally within the body and coupled to the terminal pin, the conductor member rotatable relative to the body;
• and
• a distal assembly coupled to the distal end of the body and including:
• a housing having a distal region and a proximal region, the proximal region fixedly coupled to the distal end of the body;
• a helical electrode including a fixation portion and an attachment portion, the helical electrode formed of a filar having a circular cross-sectional profile;
• a coupler rotatably disposed within the housing, the coupler having a proximal region and a distal region, the proximal region connected to the conductor member, the distal region of the coupler including an outer surface defining a helical groove complementary to the attachment portion of the helical electrode such that the attachment portion of the helical electrode can be threaded onto the distal region of the coupler;
• and
• a weld further securing the attachment portion of the helical electrode to the distal region of the coupler;
• wherein the terminal pin is rotatably engaged with the coupler via the conductor member such that rotation of the terminal pin causes the coupler and the helical electrode to rotate and therefore translate relative to the housing.