A system for detecting the position of a catheter in a patient includes three sets of reference electrodes, with one set disposed on each of the mutually orthogonal X, Y and Z axes. A signal processor measures the differential voltage indicative of impedance between a detection electrode disposed on the catheter and each electrode of each of the three sets of reference electrodes in order to determine the X coordinate, Y coordinate and Z coordinate of the catheter. The detected position of the catheter is recorded and the detection of subsequent catheter positions is performed relative to the recorded catheter position. The difference between subsequent catheter positions and the recorded position relative to the X, Y and Z axes is displayed in order to facilitate re-positioning of the catheter at the recorded position. Optional EKG and/or respiratory sensors may be used to synchronize the catheter position detection in order to reduce detection inaccuracies due to EKG and/or respiratory artifacts.