An advancer system is described for moving an elongate medical device within a body. The system includes a drive unit having a motor. The drive unit is configured to translate movement of the motor to the device so as to alternately advance and retract the device relative to the body. The advancer system also includes a user-operable control system configured to control the drive unit. The control system can interface with a magnetic navigation system. The above-described system allows an operating physician to control catheter advancement and retraction while remaining outside an x-ray imaging field. Thus the physician is freed from repeated x-ray exposure.