Patent ID: 6970743

Claim:
An implantable cardiac stimulation device, comprising: a physiological sensor that detects a physiologic parameter associated with a diurnal state of the patient; a QT measuring circuit that measures a QT interval based on at least one of an evoked cardiac event or an intrinsic cardiac event; a pulse generator that delivers pacing pulses to at least one chamber of the patient's heart at an adjustable pacing rate; a control circuit connected to the physiological sensor, pulse generator, and to the QT measuring circuit, wherein the control circuit is operative to process the physiological parameter to determine the diurnal state, and that is operative to determine when the measured QT interval is abnormally lone for the diurnal state, and that is operative to adjust the pacing rate to shorten the QT interval to within a normal range; wherein the control circuit increases the pacing rate when a measured QT interval exceeds a QT Threshold; and a memory circuit for storing a QT sleep threshold and a QT awake threshold; and wherein the control circuit uses the stored QT sleep threshold as the QT Threshold when the patient is in a sleep state, and uses the QT awake threshold as the QT Threshold when the patient is in an awake state.