A method and device of distinguishing premature contractions that includes a sensor sensing cardiac signals, and a processor configured to determine a plurality of intervals in response to the sensed cardiac signal, detect a premature contraction being associated with a first R-wave of the plurality of R-waves, determine whether a metric of the first R-wave is greater than a premature contraction threshold, and identify the detected premature contraction as one of a premature atrial contraction or a premature ventricular contraction in response to determining whether a metric of the first R-wave is greater than a premature contraction threshold.
