The present invention regards a monitoring device (10) for monitoring and evaluating electrogram signals representing electric activities of a heart chamber, said monitoring device (10) comprising a signal input (22) operatively connected to a mapping catheter (12) and a signal processing and evaluation unit (24) for processing and evaluating electrogram signals received at the signal input (22). The mapping catheter (12) is equipped with one or more electrode poles (18) for picking up electric potentials and generating electrogram signals from the picked up electric potentials. The signal processing and evaluation unit (24) is configured to perform a number of steps when an electrogram signal is received by the signal input (22). The steps include identifying waveform deflections in the electrogram signal, measuring deflection intervals between each pair of consecutive deflection complexes in the electrogram signal, measuring at least one metric that characterizes a morphology of a deflection complex in the electrogram signal, generating a multi-dimensional deflection vector of at least two dimensions for each identified deflection, wherein at least one element is the deflection interval, determining a distance between each pair of consecutive deflections from the multi-dimensional deflection vectors, and determining a cumulative distance between deflections in a time window of predetermined length.
