Described embodiments include an apparatus, including adisplay and a processor. The processor is configured tonavigate a catheter to a particular location within a body of asubject, using each one of a plurality of electrodes coupled tothe body of the subject. The processor is further configured toidentify, subsequently, from a signal that represents animpedance between a given pair of the electrodes, that a phrenicnerve of the subject was stimulated by a pacing current passedfrom the catheter into tissue of the subject at the particularlocation, and to generate an output on the display, in responseto the identifying. Other embodiments are also described.
