A method including calculating, at multiple intra-cardiac locations, respective average atrial fibrillation cycle-length (AFCL) values. A determination is made as to whether the calculated average AFCL values are indicative of a regular atrial fibrillation (AF) activity. Gradients between pairs of the average AFCL values are calculated for a plurality of average AFCL values that are determined to be indicative of regular AF activity. The calculated AFCL gradients are presented to a user, overlaid on a map of at least a portion of the heart.
