1. A method of operating an implantable medical device (IMD) comprising a neurostimulator coupled to an electrode assembly, said neurostimulator adapted to deliver a stimulation signal at a plurality of intensity parameter levels at predefined increments, said method comprising: monitoring a heart rate of a patient implanted with the IMD; delivering to the patient a first set of stimulation signals at a first frequency, wherein said delivering comprises incrementally increasing the intensity parameter level by the predefined increment for subsequent stimulation signals until bradycardia is detected; wherein if tachycardia is detected in response to the stimulation signal having an intensity parameter level one predefined increment below the intensity parameter level at which bradycardia is detected, delivering to the patient a second set of stimulation signals at a second frequency lower than the first frequency, wherein said delivering the second set of stimulation signals comprises incrementally increasing the intensity parameter level by the predefined increment for subsequent stimulation signals until bradycardia is detected; wherein if a transition heart rate response is detected in response to the stimulation signal having an intensity parameter level one predefined increment below the intensity parameter level at which bradycardia is detected, identifying the stimulation signal resulting in the transition heart rate response as corresponding to a neural fulcrum zone.