A computer-implemented method of identifying one or more focal source locations (50, 735, 755, 1110) of electrophysiological activity for a heart using intracardiac electrograms of the heart, the method comprising: receiving a first electrical signal set obtained from a first location of the heart, wherein the first electrical signal set comprises a unipolar electrogram (54, 64, 564) and a bipolar electrogram (52, 62, 562, 582); determining that the first electrical signal set is periodic; identifying a periodicity cycle length of the first electrical signal set if the first electrical signal set is periodic; characterized in that the method further comprises: identifying a plurality of peaks (56, 66, 505, 566, 586) in the bipolar electrogram (52, 62, 562, 582) of the first electrical signal set that are associated with the identified periodicity cycle length; for a given peak (56, 66, 505, 566, 586) in the identified plurality of peaks, analyzing a peak morphology by: identifying a unipolar electrogram portion (58, 68) in the unipolar electrogram (54, 64) corresponding to the given peak (56, 66, 505, 566, 586); and analyzing the identified unipolar electrogram portion (58, 68) to identify the peak morphology of the given peak (56, 66, 505, 566, 586); and identifying the first location in the heart as a first focal source location of the one or more focal source locations (50, 735, 755, 1110) when the identified periodicity cycle length and the identified plurality of peaks (56, 66, 505, 566, 586) have focal source characteristics, wherein the focal source characteristics comprise at least a threshold percentage of peak morphologies in the first electrical signal set being associated with the identified plurality of peaks (56, 66, 505, 566, 586) having a QS morphology. receiving a first electrical signal set obtained from a first location of the heart, wherein the first electrical signal set comprises a unipolar electrogram (54, 64, 564) and a bipolar electrogram (52, 62, 562, 582); determining that the first electrical signal set is periodic; identifying a periodicity cycle length of the first electrical signal set if the first electrical signal set is periodic; identifying a plurality of peaks (56, 66, 505, 566, 586) in the bipolar electrogram (52, 62, 562, 582) of the first electrical signal set that are associated with the identified periodicity cycle length; for a given peak (56, 66, 505, 566, 586) in the identified plurality of peaks, analyzing a peak morphology by: identifying a unipolar electrogram portion (58, 68) in the unipolar electrogram (54, 64) corresponding to the given peak (56, 66, 505, 566, 586); and analyzing the identified unipolar electrogram portion (58, 68) to identify the peak morphology of the given peak (56, 66, 505, 566, 586); and identifying a unipolar electrogram portion (58, 68) in the unipolar electrogram (54, 64) corresponding to the given peak (56, 66, 505, 566, 586); and analyzing the identified unipolar electrogram portion (58, 68) to identify the peak morphology of the given peak (56, 66, 505, 566, 586); and identifying the first location in the heart as a first focal source location of the one or more focal source locations (50, 735, 755, 1110) when the identified periodicity cycle length and the identified plurality of peaks (56, 66, 505, 566, 586) have focal source characteristics, wherein the focal source characteristics comprise at least a threshold percentage of peak morphologies in the first electrical signal set being associated with the identified plurality of peaks (56, 66, 505, 566, 586) having a QS morphology.