A method, including, receiving a first group of electrocardiograph (ECG) signals derived from a single heartbeat and generated at a respective plurality of electrodes on a catheter in a heart of a subject, formulating a template relating times of annotations of the first group of the ECG signals, and assigning the template an index. The method further includes receiving a second group of ECG signals derived from a subsequent single heartbeat and generated at the electrodes, calculating times of annotations of the second group, formulating a comparison between the template and the times of annotations of the second group, and, when the comparison indicates that the times of annotations of the second group correspond to the template, assigning the index to the second group of ECG signals, and presenting graphically on a display an occurrence of the template relative to a timeline representing heartbeats from the heart.