A system of determining regions of interest for cardiac ablation using fractionation, comprising: a plurality of sensors (208, 210), each configured to detect one of a plurality of electro-cardiogram signals over time, each ECG signal indicating electrical activity of a heart; a processing device comprising one or more processor configured to: determine, for each of the plurality of ECG signals, one or more local activation times (LATs) each indicating a time of activation of a corresponding ECG signal; generate, based on the determined one or more LATs of each of the plurality of ECG signals, one or more driver maps and one or more perpetuator maps, each representing the electrical activity of the heart; derive parameters (401, 402) from the driver and perpetuator maps (328, 330), using at least fractionation, wherein deriving the parameters comprises: filtering the LATs and removing non-fractionated LATs comprising non-fractionated single, short double and long double potentials; finding windows of fractionation using the filtered LATs; and producing fractionated ECGs using the windows of fractionation; process and combine the derived parameters into driver evidence and perpetuator evidence; and determine the regions of interest for cardiac ablation in accordance with the fractionation used to derive the driver evidence and the perpetuator evidence; and a display device. a plurality of sensors (208, 210), each configured to detect one of a plurality of electro-cardiogram signals over time, each ECG signal indicating electrical activity of a heart; a processing device comprising one or more processor configured to: determine, for each of the plurality of ECG signals, one or more local activation times (LATs) each indicating a time of activation of a corresponding ECG signal; generate, based on the determined one or more LATs of each of the plurality of ECG signals, one or more driver maps and one or more perpetuator maps, each representing the electrical activity of the heart; derive parameters (401, 402) from the driver and perpetuator maps (328, 330), using at least fractionation, wherein deriving the parameters comprises: filtering the LATs and removing non-fractionated LATs comprising non-fractionated single, short double and long double potentials; finding windows of fractionation using the filtered LATs; and producing fractionated ECGs using the windows of fractionation; process and combine the derived parameters into driver evidence and perpetuator evidence; and determine the regions of interest for cardiac ablation in accordance with the fractionation used to derive the driver evidence and the perpetuator evidence; and a display device. determine, for each of the plurality of ECG signals, one or more local activation times (LATs) each indicating a time of activation of a corresponding ECG signal; generate, based on the determined one or more LATs of each of the plurality of ECG signals, one or more driver maps and one or more perpetuator maps, each representing the electrical activity of the heart; derive parameters (401, 402) from the driver and perpetuator maps (328, 330), using at least fractionation, wherein deriving the parameters comprises: filtering the LATs and removing non-fractionated LATs comprising non-fractionated single, short double and long double potentials; finding windows of fractionation using the filtered LATs; and producing fractionated ECGs using the windows of fractionation; filtering the LATs and removing non-fractionated LATs comprising non-fractionated single, short double and long double potentials; finding windows of fractionation using the filtered LATs; and producing fractionated ECGs using the windows of fractionation; process and combine the derived parameters into driver evidence and perpetuator evidence; and determine the regions of interest for cardiac ablation in accordance with the fractionation used to derive the driver evidence and the perpetuator evidence; and a display device.