A maximum pacing rate is dynamically established during single-chamber
atrial pacing of a heart by a rate control system within a single-chamber
or dual-chamber cardiac stimulation device which paces the atria of a
heart on demand at the end of an escape interval. The system includes a
detector that detects an atrial activation of the heart and an R wave of
the heart corresponding to the detected atrial activation. The system
further includes a rate limit circuit that determines a minimum RA
interval and extends the escape interval to an extended escape interval
to end with the minimum RA interval.