The invention discloses conducting cardiac catheterization with a probe having a plurality of sensors. The heart is displayed as a first graphic image. Signals from the sensors are processed accordingto a predefined algorithm to generate respective outputs. A region on the first graphic image that is less than all of the first graphic image is selected according to locations of the sensors, and values derived from outputs of the sensors are displayed on the selected region as a second graphic image. Thereafter, the second graphic image is removed and replaced by an updated version.