3d electrical activity representation

In one embodiment, a medical system includes a catheter including electrodes, and configured to be inserted into a chamber of a heart and maneuvered among sampling sites to sample electrical activity, a display, and processing circuitry to receive signals provided by the catheter, and compute, for each sampling site, a sampling position of the catheter and respective electrode positions of the catheter electrodes, render to the display a 3D representation of the chamber including respective sampling-site markers indicating the computed sampling position of the catheter at respective ones of the sampling sites, receive a user input selecting one sampling-site marker, and update the 3D representation to include electrode markers indicating the respective electrode positions of the respective catheter electrodes while the catheter was sampling the electrical activity of the tissue at the sampling site corresponding to the selected sampling-site marker.