A device for detecting points and/or regions of rotational electrophysiological activity in or on a heart comprises an input for receiving spatiotemporal electrophysiological data corresponding to a plurality of spatial locations in or on the heart, a time feature extractor for providing time values indicative of times of occurrence of a predetermined feature of a plurality of electric potential waveforms at the spatial location, a mapping unit for providing pairs of adjacent spatial locations; a directed graph generator for generating a directed graph comprising directed edges; a topological feature analyzer.