An implantable pulse generator system includes a nerve stimulation unit providing vagal nerve stimulation (VNS) pulses； an autonomic tone sensor which determines the patient's autonomic status； and a control unit connected to the nerve stimulation unit and the autonomic tone sensor. The control unit controls the nerve stimulation unit to generate VNS with varying intensity, depending on the autonomic status (which is evaluated in a moving window). The control unit gradually increases VNS intensity when the autonomic status indicates a shift toward more sympathetic dominance, and it gradually decreases VNS intensity when the autonomic status indicates a shift toward more parasympathetic dominance, wherein the gradual increase and the gradual decrease of the VNS intensity follow two different paths.
