Patent ID: 7711415

Claim:
For use with an implantable device, a method for independently monitoring levels of parasympathetic and sympathetic tone of a patient, comprising: (a) sensing a cardiac electrogram (EGM) signal using implanted electrodes; (b) measuring cardiac intervals within a portion of the sensed EGM signal; and (c) independently assessing levels of parasympathetic tone and sympathetic tone based on the measured cardiac intervals, wherein step (c) comprises: (c.1) assessing the level of parasympathetic tone in one of the following manners: (c.1.i) determining the patient's diurnal variation of cardiac intervals based on the measured cardiac intervals, wherein diurnal variation of cardiac intervals is a measurement of change in cardiac intervals over the course of a day, and assessing the level of parasympathetic tone based on the diurnal variation of cardiac intervals; (c.1.ii) determining the patient's diurnal variation of heart rate based on the measured cardiac intervals, wherein diurnal variation of heart rate is a measurement of change in heart rate over the course of a day, and assessing the level of parasympathetic tone based on the diurnal variation of heart rate; and (c.1.iii) identifying each said cardiac interval that is longer than the immediately preceding cardiac interval as being indicative of cardiac deceleration, and assessing the level of parasympathetic tone based on the cardiac intervals that are identified as being indicative of cardiac deceleration; and (c.2) assessing the patient's level of sympathetic tone in one of the following manners (c.2.i) determining the patient's average cardiac interval based on the measured cardiac intervals, and assessing the level of sympathetic tone based on the determined average cardiac interval; (c.2.ii) determining the patient's average heart rate based on the measured cardiac intervals, and assessing the level of sympathetic tone based on the determined average heart rate; and (c.2.iii) identifying each said cardiac interval that is shorter than the immediately preceding cardiac interval as being indicative of cardiac acceleration, and assessing the level of sympathetic tone based on the cardiac intervals that are identified as being indicative of cardiac acceleration.