A lead having an extendable and retractable fixation mechanism has a
rotating terminal pin at the terminal end which rotates the fixation
mechanism at the distal end. As the terminal pin is rotated, the fixation
mechanism is extended or retracted from the distal end of the lead. A
threaded collar allows for the fixation mechanism to smoothly extend and
retract from the lead, and allows for a 1:1 turn ratio between the
terminal pin and the fixation mechanism. A fluoroscopic ring disposed at
the distal end of the lead provides information during the implantation
process.