A cardiac rhythm management system provides both a safe maximum pacing rate limit
and a physiological maximum pacing rate limit. The present subject matter provides
a solution to problems associated with the use of a single maximum tracking rate
(MTR). In one embodiment, the present subject matter utilizes two MTRs, where the
first is a normal MTR and the second is a hysteresis MTR. In one embodiment, the
hysteresis MTR is set higher than the normal MTR. The hysteresis MTR functions
as a maximum pacing rate limit while tracking an atrial rate until the atrial rate
exceeds the hysteresis MTR limit. When the atrial rate exceeds the hysteresis MTR
limit, the maximum pacing rate limit is set to the normal MTR. Once the atrial
rate falls below a predetermined threshold, the maximum pacing rate limit is set
to the hysteresis MTR. The predetermined threshold may be set to the normal MTR,
the hysteresis MTR, or other rates. In one embodiment, changing the maximum pacing
rate limit in this fashion allows for uninterrupted pacing treatment for patients,
such as congestive heart failure (CHF) patients, who may display fast but physiologically
normal heart rates and need cardiac resynchronization therapy (CRT) at such fast
heart rates. Such a pacing treatment provides for a more rapid and natural maximum
pacing rate limit for the patient, while still protecting the patient from being
paced at abnormally high rates.
