An analyzer automatically analyzes both, a common portion of multiple successive heart cycles of electrophysiological signal data synchronized with respect to a P wave and a common portion of multiple successive heart cycles of the signal data synchronized with respect to an R wave, to identify changes occurring in amplitude value and time duration of the common portion of the multiple successive heart cycles of the signal data. A display processor initiates generation of at least one display image showing the common portion of the multiple successive heart cycles synchronized in time, adjacent and mutually vertically displaced to facilitate visual comparison and highlighting an identified change by a visual attribute.