A method of atrial focal source detection is provided which includesdetecting,via sensors, electro-cardiogram (ECG) signals over time. Each ECG signal isdetected via one of the sensors and indicates electrical activity of a heart.Themethod also includes determining, for each ECG signal, local activation times(LATs) each indicating a time of one of a plurality of atrial activations of acorresponding ECG signal and detecting whether one or more focal source areasofactivation in the heart is indicated based on the detected ECG signals and theoneor more local LATs. S-waves can be distinguished from non-S-waves bygeneratingmodels for each atrial activation and classifying atrial activations. Maps canbegenerated by visually indicating, for each sensor, a level of incidence of theatrialactivations occurring before atrial activations of neighboring sensors withina periodof time.
