A method and system for determining activation times for electric potentials from complex electrograms to identify the location of arrhythmic sources or drivers. The method includes counting a number deflections in a recorded cardiac electrogram signal from at least one electrode for a predetermined amount of time. A deflection time is identified for each of the counted number of deflections. A most negative slope is identified between each of the identified deflections times. Each of the identified most negative slopes is correlated to a possible activation time. Each possible activation time is associated with a corresponding electrode from the at least one electrode. A spatial voltage gradient at each corresponding electrode is calculated for each possible activation time. The greatest spatial voltage gradient is identified. The greatest spatial voltage gradient is correlated to an activation time.
