Various embodiments concern an implantable lead having a coil electrode, configured to deliver defibrillation therapy, made from filars wound in a helical pattern to have a pitch. An end of the coil electrode can be received within a lumen of a tubular fitting, the lumen having threading that corresponds to the pitch of the filars. A wall of a polymer sleeve extending over the coil electrode can be pinched between the threading of the lumen and the filars to mechanically couple the polymer sleeve to the tubular fitting. The polymer sleeve can be porous to permit delivery of the defibrillation through the wall to tissue. Reception of the polymer sleeve within the lumen of the tubular fitting can allow the entire coil electrode to be within the polymer sleeve to prevent direct contact between tissue and the coil electrode.
