Nerve signal differentiation in cardiac therapy

Abstract

Methods of nerve signal differentiation, methods of delivering therapy using such nerve signal differentiation, and to systems and devices for performing such methods. Nerve signal differentiation may include locating two electrodes proximate nerve tissue and differentiating between efferent and afferent components of nerve signals monitored using the two electrodes.

1 . An implantable medical device for delivering cardiac therapy comprising:
 monitoring apparatus configured to monitor physiological parameters of a patient, wherein the monitoring apparatus comprises at least two electrodes configured to monitor electrical activity of the patient's vagus nerve;   a sensing module operably coupled to the monitoring apparatus and configured to receive the monitored physiological parameters;   a therapy delivery module configured to deliver cardiac therapy to the patient;   control module operably coupled to the sensing module and to the therapy delivery module and configured to:   differentiate between efferent activity and afferent activity of the monitored electrical activity of the patient's vagus nerve,   
       analyze the monitored physiological parameters by at least determining whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced over time, and
 initiate or adjust cardiac therapy to the patient if the efferent activity of the electrical activity of the patient's vagus nerve is reduced. 
 
     
     
         2 . The device of  claim 1 , wherein the control module is configured to determine whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced by at least comparing the pulses per second of the efferent activity to a selected value. 
     
     
         3 . The device of  claim 1 , wherein the control module is configured to determine whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced by at least comparing the pulses per second of presently-monitored efferent activity to the pulses per second of previously-monitored efferent activity. 
     
     
         4 . The device of  claim 1 , wherein the control module is further configured to:
 determine whether the monitored electrical activity of the patient's vagus nerve comprises afferent activity, and   determine whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced by at least comparing the efferent activity to the afferent activity.   
     
     
         5 . The device of  claim 1 , wherein the control module is configured to determine whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced by at least comparing the average amplitude of a selected frequency range of the efferent activity to a selected value. 
     
     
         6 . The device of  claim 1 , wherein the control module is configured to determine whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced by at least comparing the average amplitude of a selected frequency range of the presently-monitored efferent activity to the average amplitude of the selected frequency range of previously-monitored efferent activity. 
     
     
         7 . The device of  claim 1 , wherein the control module is configured to determine whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced by at least comparing the average power of a selected frequency range of the efferent activity to a selected value. 
     
     
         8 . The device of  claim 1 , wherein the control module is configured to determine whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced by at least comparing the average power of a selected frequency range of the presently-monitored efferent activity to the average power of the selected frequency range of previously-monitored efferent activity. 
     
     
         9 . The device of  claim 1 , wherein the cardiac therapy comprises electrical stimulation to the patient's vagus nerve, and wherein the control module is further configured to deliver electrical stimulation to the patient's vagus nerve after a burst of efferent activity of the electrical activity of the patient's vagus nerve ceases. 
     
     
         10 . The device of  claim 1 , wherein the physiological parameters further comprise electrical activity of the patient's heart, and wherein the control module is further configured to:
 provide a function relating the status of the patient's vagus nerve to the electrical activity of the patient's heart for use in therapy,   assess a status of the patient's vagus nerve using the monitored electrical activity of the patient's heart using the function, and   
       initiate or adjust cardiac therapy to the patient based on the assessed status of the patient's vagus nerve. 
     
     
         11 . A method of delivering therapy, wherein the method comprises:
 monitoring physiological parameters of a patient, wherein the physiological parameters comprise electrical activity of the patient's vagus nerve;   determining whether the monitored electrical activity of the patient's vagus nerve comprises efferent activity;   
       analyzing the monitored physiological parameters, wherein analyzing the monitored physiological parameters comprises determining whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced over time; and 
       initiating or adjusting cardiac therapy if the efferent activity of the electrical activity of the patient's vagus nerve is reduced. 
     
     
         12 . The method of  claim 11 , wherein determining whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced comprises comparing the pulses per second of the efferent activity to a selected value. 
     
     
         13 . The method of  claim 11 , wherein determining whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced comprises comparing the pulses per second of presently-monitored efferent activity to the pulses per second of previously-monitored efferent activity. 
     
     
         14 . The method of  claim 11 , wherein the method further comprises determining whether the monitored electrical activity of the patient's vagus nerve comprises afferent activity, and wherein determining whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced comprises comparing the efferent activity to the afferent activity. 
     
     
         15 . The method of  claim 11 , wherein determining whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced comprises comparing the average amplitude of a selected frequency range of the efferent activity to a selected value. 
     
     
         16 . The method of  claim 11 , wherein determining whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced comprises comparing the average amplitude of a selected frequency range of the presently-monitored efferent activity to the average amplitude of the selected frequency range of previously-monitored efferent activity. 
     
     
         17 . The method of  claim 11 , wherein determining whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced comprises comparing the average power of a selected frequency range of the efferent activity to a selected value. 
     
     
         18 . The method of  claim 11 , wherein determining whether the efferent activity of the electrical activity of the patient's vagus nerve is reduced comprises comparing the average power of a selected frequency range of the presently-monitored efferent activity to the average power of the selected frequency range of previously-monitored efferent activity. 
     
     
         19 . The method of  claim 11 , wherein delivering cardiac therapy comprises delivering electrical stimulation to the patient's vagus nerve, and wherein the method further comprises delivering the electrical stimulation to the patient's vagus nerve for a selected period of time after a burst of efferent activity of the electrical activity of the patient's vagus nerve ceases. 
     
     
         20 . The method of  claim 11 , wherein the physiological parameters further comprise electrical activity of the patient's heart, and wherein the method further comprises:
 providing a function relating the status of the patient's vagus nerve to the electrical activity of the patient's heart for use in therapy,   assessing a status of the patient's vagus nerve using the monitored electrical activity of the patient's heart using the function, and   initiating or adjusting cardiac therapy to the patient based on the assessed status of the patient's vagus nerve.   
     
     
         21 - 37 . (canceled)