Apparatus for assessing scarring of cardiac tissue, consisting of a probe and a processor. The probe has one or more electrodes, which are configured to contact the tissue at a plurality of positions and to sense respective voltages in the tissue at the positions. The processor receives the respective voltages, and computes a triangular mesh that is representative of a surface of the tissue and that consists of multiple triangles having vertices corresponding to the positions contacted by the one or more electrodes. The processor calculates respective scar areas within the triangles by comparing the respective voltages sensed at the positions corresponding to the vertices to a predefined range of the voltages that is associated with scarring, and computes a sum of the respective areas. The processor compares the sum to a total area of the triangles so as to assess a degree of the scarring of the tissue.
