A computer implemented method and system for declaring arrhythmias in cardiac activity are provided. The method and system are under control of one or more processors that are configured with specific executable instructions. The method and system obtain far field cardiac activity (CA) signals for a series of beats and builds an N-dimensional data set from data values for features of interest from the CA signals. The method and system utilize a manifold structure to map the N-dimensional data set, through nonlinear dimensional reduction, onto an M-dimensional data set and declares an atrial fibrillation (AFL) episode based on a relation between the M-dimensional data set and one or more AFL classification criteria.
