The supraventricular rhythm of a patient's heart is characterized using
cardiac beats collected during a plurality of time periods, some of which
are noncontiguous. Pacing parameters may be modified to allow the
development of a spontaneous rhythm. Waveforms of the collected cardiac
beats are stored for later processing, or are combined with previously
collected beats and the combination is stored. When a sufficient number
of cardiac beats are collected, the patient's supraventricular rhythm is
characterized using the collected cardiac beats.