Vagus nerve stimulation and subcutaneous defibrillation system

Abstract

Systems and methods are provided for delivering vagus nerve stimulation and cardioversion/defibrillation therapies to patients for treating chronic heart failure. The vagus nerve stimulation and cardioversion/defibrillation therapies may be provided using a single implantable pulse generator, which can coordinate delivery of the therapies to provide an acute vagus nerve stimulation therapy in advance of delivering cardioversion-defibrillation energy.

1 - 20 . (canceled) 
     
     
         21 . An implantable neurostimulation system, comprising:
 a pulse generator comprising a vagus nerve stimulation (VNS) subsystem and an implantable cardioverter-defibrillator (ICD) subsystem; and   a control system comprising a processor configured to:
 activate the VNS subsystem to deliver a chronic VNS therapy to a patient, wherein delivering the chronic VNS therapy comprises:
 delivering a stimulation signal having an ON time and an OFF time; 
 monitoring a baseline heart rate signal acquired by a heart rate sensor during the OFF time of the stimulation signal; 
 monitoring a heart rate response signal acquired by the heart rate sensor during the ON time periods of the stimulation signal; and 
 in response to the monitored baseline heart rate signal and the monitored heart rate response signal, adjusting one or more parameters of the stimulation signal to deliver the stimulation signal in the patient's neural fulcrum zone, the neural fulcrum zone corresponding to a stimulation intensity during which a transition heart rate response is detected, the transition heart rate response being between tachycardia and bradycardia and comprising a heart rate change of between 0% and 5%; 
 
 in response to a detection of a cardiac event, activate the VNS subsystem to deliver an acute anti-arrhythmic VNS therapy different from the chronic VNS therapy to the patient; and 
 in response to a continuation of the cardiac event after delivery of the acute anti-arrhythmic VNS therapy, activate the ICD subsystem to deliver electrical cardioversion-defibrillation energy to the patient. 
   
     
     
         22 . The system of  claim 21 , wherein the VNS subsystem is configured to deliver the acute anti-arrhythmic VNS therapy by applying a higher intensity electrical stimulation than the chronic VNS therapy. 
     
     
         23 . The system of  claim 21 , further comprising a housing containing the pulse generator, wherein the housing comprises a conductive electrode coupled to the ICD subsystem. 
     
     
         24 . The system of  claim 23 , further comprising a single lead assembly coupled to the pulse generator comprising a VNS electrode, a first ICD electrode, and a second ICD electrode. 
     
     
         25 . The system of  claim 24 , wherein the VNS electrode is provided at an end of the single lead assembly distal from the pulse generator, and wherein the first ICD electrode is provided at an intermediate location on the single lead assembly between the pulse generator and the VNS electrode. 
     
     
         26 . The system of  claim 25 , wherein the second ICD electrode is provided at a second intermediate location on the single lead assembly between the pulse generator and the VNS electrode. 
     
     
         27 . The system of  claim 21 , wherein the cardiac event detected is an arrhythmia suitable for treatment with defibrillation. 
     
     
         28 . The system of  claim 21 , wherein the stimulation signal of the chronic VNS therapy has a frequency between 2 hz and 20 hz. 
     
     
         29 . The system of  claim 21 , wherein the stimulation signal of the chronic VNS therapy has a duty cycle between 15% and 30%. 
     
     
         30 . An implantable neurostimulation system, comprising:
 a heart rate sensor configured to detect a cardiac event;   a pulse generator comprising a vagus nerve stimulation (VNS) subsystem and an implantable cardioverter-defibrillator (ICD) subsystem; and   a control system comprising a processor configured to:
 activate the VNS subsystem to deliver a chronic VNS therapy to a patient, wherein delivering the chronic VNS therapy comprises:
 delivering a stimulation signal having an ON time and an OFF time; 
 monitoring a baseline heart rate signal acquired by the heart rate sensor during the OFF time of the stimulation signal; 
 monitoring a heart rate response signal acquired by the heart rate sensor during the ON time periods of the stimulation signal; and 
 in response to the monitored baseline heart rate signal and the monitored heart rate response signal, adjusting one or more parameters of the stimulation signal to deliver the stimulation signal in the patient's neural fulcrum zone, the neural fulcrum zone corresponding to a stimulation intensity during which a transition heart rate response is detected, said transition heart rate response being between tachycardia and bradycardia and comprising a heart rate change of between 0% and 5%; 
 
 in response to a detection of the cardiac event, activate the VNS subsystem to deliver an acute anti-arrhythmic VNS therapy different from the chronic VNS therapy to the patient; and 
 in response to a continuation of the cardiac event after delivery of the acute anti-arrhythmic VNS therapy, activate the ICD subsystem to deliver electrical cardioversion-defibrillation energy to the patient. 
   
     
     
         31 . The system of  claim 30 , wherein the VNS subsystem is configured to deliver the acute anti-arrhythmic VNS therapy by applying a higher intensity electrical stimulation than the chronic VNS therapy. 
     
     
         32 . The system of  claim 30 , further comprising a housing containing the pulse generator, wherein the housing comprises a conductive electrode coupled to the ICD subsystem. 
     
     
         33 . The system of  claim 32 , further comprising a single lead assembly coupled to the pulse generator comprising a VNS electrode, a first ICD electrode, and a second ICD electrode. 
     
     
         34 . The system of  claim 33 , wherein the heart rate sensor includes a sensing electrode provided at an intermediate location on the single lead assembly between the pulse generator and the first ICD electrode. 
     
     
         35 . The system of  claim 31 , wherein the cardiac event detected is an arrhythmia suitable for treatment with defibrillation. 
     
     
         36 . A method of operating an implantable neurostimulation system comprising a pulse generator including a vagus nerve stimulation (VNS) subsystem and an implantable cardioverter-defibrillator (ICD) subsystem, the method comprising:
 activating the VNS subsystem to deliver a chronic VNS therapy to a patient, wherein delivering the chronic VNS therapy comprises:
 delivering a stimulation signal having an ON time and an OFF time; 
 monitoring a baseline heart rate signal acquired by a heart rate sensor during the OFF time of the stimulation signal; 
 monitoring a heart rate response signal acquired by the heart rate sensor during the ON time periods of the stimulation signal; and 
 in response to the monitored baseline heart rate signal and the monitored heart rate response signal, adjusting one or more parameters of the stimulation signal to deliver the stimulation signal in the patient's neural fulcrum zone, the neural fulcrum zone corresponding to a stimulation intensity during which a transition heart rate response is detected, the transition heart rate response being between tachycardia and bradycardia and comprising a heart rate change of between 0% and 5%; 
   in response to a detection of a cardiac event, activating the VNS subsystem to deliver an acute anti-arrhythmic VNS therapy different from the chronic VNS therapy to the patient; and   in response to a continuation of the cardiac event after delivery of the acute anti-arrhythmic VNS therapy, activating the ICD subsystem to deliver electrical cardioversion-defibrillation energy to the patient.   
     
     
         37 . The method of  claim 36 , wherein the VNS subsystem is configured to deliver the acute anti-arrhythmic VNS therapy by applying a higher intensity electrical stimulation than the chronic VNS therapy. 
     
     
         38 . The method of  claim 36 , wherein the stimulation signal of the chronic VNS therapy has a frequency between 2 hz and 20 hz. 
     
     
         39 . The method of  claim 36 , wherein the stimulation signal of the chronic VNS therapy has a duty cycle between 15% and 30%. 
     
     
         40 . The method of  claim 36 , wherein the cardiac event detected is an arrhythmia suitable for treatment with defibrillation.