A decision support computer system, computer-implemented method and computer program product for supporting diagnostic analysis of potential ablation areas to cure atrial flutter. An interface component (110) receives an electrical reference signal (RS) generated by a reference sensor (CSCS). The reference signal (RS) provides a time reference for electrical activity of one or more atria of a patient wherein the time interval between two subsequent electrical activities is referred to as basic cycle length (BCL). Further, it receives a plurality of electrical signals (P1 to Pi) generated by one or more further sensors (S1 to Sn) wherein the plurality of electrical signals (P1 to Pi) relate to a plurality of locations in the one or more atria. The plurality of locations includes locations different from the location of the reference sensor (CSCS). A signal analyzer component (120) determines, for each signal of at least a subset of the received signals originating from locations within a selected area of the one or more atria, when electrical activity occurs. Further, it determines, for a plurality of time points within the basic cycle length, size values for respective areas of active tissue by aggregating the size of surface elements associated with the locations where the respective signals show activity at the respective time points. A visualizer component (130) sets a visual property value for at least a subset of the surface elements wherein the subset includes surface elements associated with locations defining a particular area of active tissue which is smaller than active tissue areas associated with other locations. The visual property value indicates, in a visualization of the selected area, the particular area of active tissue as a potential ablation area to cure atrial flutter.
