A stimulation device for managing tachyarrhythmic risk during sleep through vagus nerve stimulation, comprising: an implantable neurostimulator comprising a pulse generator configured to deliver electrical therapeutic stimulation in a manner that results in creation and propagation of action potentials within neuronal fibers comprising a patient's cervical vagus nerve (15, 16); means configured to store operating modes of the pulse generator in a recordable memory, comprising: means configured to parametrically define a maintenance dose of the electrical therapeutic stimulation tuned to restore cardiac autonomic balance through continuously-cycling, intermittent and periodic electrical pulses at an intensity that avoids acute physiological side effects and with an unchanging cycle not triggered by physiological markers; means configured to parametrically define a boost dose of the electrical therapeutic stimulation tuned to prevent initiation of or disrupt tachyarrhythmia through periodic electrical pulses delivered at higher intensity than the maintenance dose; means configured to therapeutically deliver the maintenance dose to the vagus nerve (15, 16) independent of cardiac cycle via a pulse generator comprised in the implantable neurostimulator through at least a pair of helical electrodes electrically coupled to the pulse generator via a nerve stimulation therapy lead; and means configured to monitor the patient's physiological state via at least one sensor comprised in the implantable neurostimulator, and upon sensing a condition indicative of naturally occurring bradycardia followed by a condition indicative of potential tachyarrhythmia, deliver the boost dose to the vagus nerve (15, 16) via the pulse generator through the pair of helical electrodes. an implantable neurostimulator comprising a pulse generator configured to deliver electrical therapeutic stimulation in a manner that results in creation and propagation of action potentials within neuronal fibers comprising a patient's cervical vagus nerve (15, 16); means configured to store operating modes of the pulse generator in a recordable memory, comprising: means configured to parametrically define a maintenance dose of the electrical therapeutic stimulation tuned to restore cardiac autonomic balance through continuously-cycling, intermittent and periodic electrical pulses at an intensity that avoids acute physiological side effects and with an unchanging cycle not triggered by physiological markers; means configured to parametrically define a boost dose of the electrical therapeutic stimulation tuned to prevent initiation of or disrupt tachyarrhythmia through periodic electrical pulses delivered at higher intensity than the maintenance dose; means configured to therapeutically deliver the maintenance dose to the vagus nerve (15, 16) independent of cardiac cycle via a pulse generator comprised in the implantable neurostimulator through at least a pair of helical electrodes electrically coupled to the pulse generator via a nerve stimulation therapy lead; and means configured to monitor the patient's physiological state via at least one sensor comprised in the implantable neurostimulator, and upon sensing a condition indicative of naturally occurring bradycardia followed by a condition indicative of potential tachyarrhythmia, deliver the boost dose to the vagus nerve (15, 16) via the pulse generator through the pair of helical electrodes. means configured to parametrically define a maintenance dose of the electrical therapeutic stimulation tuned to restore cardiac autonomic balance through continuously-cycling, intermittent and periodic electrical pulses at an intensity that avoids acute physiological side effects and with an unchanging cycle not triggered by physiological markers; means configured to parametrically define a boost dose of the electrical therapeutic stimulation tuned to prevent initiation of or disrupt tachyarrhythmia through periodic electrical pulses delivered at higher intensity than the maintenance dose; means configured to therapeutically deliver the maintenance dose to the vagus nerve (15, 16) independent of cardiac cycle via a pulse generator comprised in the implantable neurostimulator through at least a pair of helical electrodes electrically coupled to the pulse generator via a nerve stimulation therapy lead; and means configured to monitor the patient's physiological state via at least one sensor comprised in the implantable neurostimulator, and upon sensing a condition indicative of naturally occurring bradycardia followed by a condition indicative of potential tachyarrhythmia, deliver the boost dose to the vagus nerve (15, 16) via the pulse generator through the pair of helical electrodes.