Provided herein are implantable devices, and methods for use therewith, that independently monitor levels of parasympathetic and sympathetic tone of a patient. In accordance with an embodiment, a cardiac electrogram (EGM) signal is sensed using implanted electrodes, cardiac intervals are measured within a portion of the sensed EGM signal, and levels of parasympathetic tone and sympathetic tone are independently assessed based on the measured cardiac intervals. This abstract is not intended to describe all of the various embodiments of the present invention.