A method of evaluating an electrophysiological signal is disclosed. A mathematical reconstruction over at least one cycle of the electrophysiological signal is used to identify an abnormal substrate. A non-transitory computer readable medium is also disclosed. The nontransitory computer readable medium has stored thereon instructions for identifying a pathological substrate from a mathematical reconstruction of an electrophysiological signal, which, when executed by a processor, causes the processor to perform steps comprising using a mathematical reconstruction over many cycles of the electrophysiological signal to identify a pathological state. A system for evaluating an electrophysiological signal includes a processor configured to identify a pathological condition from a mathematical reconstruction of the electrophysiological signal. The system also includes a data input coupled to the processor and configured to provide the processor with the electrophysiological signal. The system further includes a user interface coupled to either the processor or the data input.