US Patent 6889078 Hysteresis activation of accelerated pacing

An improved pacemaker has a hysteresis feature that activates accelerated pacing during periods of sinus arrest and/or extreme bradycardia. When the patient's intrinsic heart rate drops below a hysteresis rate, the pacemaker reverts to a programmable accelerated rate or to the average cardiac rate. Accelerated pacing is delivered for a programmable period of time, after which the pacing rate is gradually reduced toward a lower rate. If a desirable intrinsic rate is not attained after the pacing rate is reduced to the lower rate, the intervention cycle repeats.