System to diagnose and manage orthostatic intolerance

Abstract

An apparatus includes a posture sensing circuit configured to detect a change in posture of a subject; a cardiac signal sensing circuit configured to generate a sensed cardiac signal, wherein the sensed cardiac signal includes heart rate information of the subject; a physiologic sensing circuit configured to generate a sensed physiologic signal, wherein the physiologic signal includes information related to blood pressure of the subject; a storage buffer; and a control circuit operatively coupled to the posture sensing circuit and the storage buffer. The control circuit is configured to initiate storage of the heart rate information and the information related to blood pressure in response to a detected change in posture of the subject.

1 . A medical device system to monitor blood pressure events of a subject, the system comprising:
 an electrical cardiac activity sensing circuit configured to sense electrical cardiac activity and generate a sensed cardiac signal indicative of the sensed electrical cardiac activity;   a heart sound sensing circuit configured to sense heart sounds indicative of mechanical cardiac activity and generate a sensed heart sound signal indicative of the sensed heart sounds;   a circular buffer configured to store the sensed cardiac signal and the sensed heart sound signal;   a storage buffer; and   a control circuit operatively coupled to the circular buffer and the storage buffer, the control circuit configured to:
 detect a blood pressure related trigger event; 
 initiate storage of the sensed cardiac signal and the sensed heart sound signal in the storage buffer in response to the detected blood pressure related trigger event and 
 generate a trend using the sensed cardiac signal and the sensed heart sound signal stored in the storage buffer. 
   
     
     
         2 . The system of  claim 1 , wherein the control circuit is configured to initiate storage of the sensed cardiac signal and the sensed heart sound signal for a time interval including the blood pressure related trigger event. 
     
     
         3 . The system of  claim 2 , wherein the time interval includes a first portion occurring prior to the blood pressure related trigger event, and a second portion occurring after the blood pressure related trigger event. 
     
     
         4 . The system of  claim 3 , further comprising a posture sensing circuit configured to detect a change in posture of the subject. 
     
     
         5 . The system of  claim 4 , wherein the blood pressure related trigger event comprises a change in posture of the subject. 
     
     
         6 . The system of  claim 4 , wherein the control circuit is configured to:
 determine a first heart rate of the sensed cardiac signal during the first portion of the time interval and a second heart rate of the sensed cardiac signal during the second portion of the time interval; and   determine a first heart sound amplitude of the sensed heart sound signal during the first portion of the time interval and a second heart sound amplitude of the sensed heart sound signal during the second portion of the time interval.   
     
     
         7 . The system of  claim 3 , further comprising an activity sensing circuit configured to detect a change in activity of a subject. 
     
     
         8 . The system of  claim 7 , wherein the blood pressure related trigger event comprises a change in activity of the subject. 
     
     
         9 . The system of  claim 1 , wherein the control circuit is configured to produce an indication when the blood pressure related trigger event has occurred. 
     
     
         10 . The system of  claim 1 , wherein the control circuit is configured to provide therapy to the subject based on the trend. 
     
     
         11 . The system of  claim 1 , wherein the control circuit is configured to determine, using the sensed cardiac signal and the sensed heart signal, one of:
 that blood pressure of the subject is less than a specified blood pressure threshold,   that a change in blood pressure of the subject is greater than a specified blood pressure change threshold, or   that the heart rate exceeds a heart rate change threshold without a change in blood pressure that exceeds a blood pressure change threshold.   
     
     
         12 . A method of monitoring blood pressure events of a subject, the method comprising:
 sensing electrical cardiac activity and generating a sensed cardiac signal indicative of the sensed electrical cardiac activity;   sensing heart sounds indicative of mechanical cardiac activity and generating a sensed heart sound signal indicative of the sensed heart sounds;   storing the sensed cardiac signal and the sensed heart sound signal in a circular buffer;   detecting a blood pressure related trigger event;   initiating storage of the sensed cardiac signal and the sensed heart sound signal in a storage buffer in response to the detected blood pressure related trigger event; and   generating a trend using the sensed cardiac signal and the sensed heart sound signal stored in the storage buffer.   
     
     
         13 . The method of  claim 12 , wherein initiating storage of the sensed cardiac signal and the sensed heart signal is done for a time interval including the blood pressure related trigger event. 
     
     
         14 . The method of  claim 13 , wherein the time interval includes a first portion occurring prior to the blood pressure trigger event, and a second portion occurring after the blood pressure related trigger event. 
     
     
         15 . The method of  claim 13 , further comprising sensing a change in posture of the subject. 
     
     
         16 . The method of  claim 14 , further comprising:
 determining a first heart rate of the sensed cardiac signal during the first portion of the time interval and a second heart rate of the sensed cardiac signal during the second portion of the time interval; and   determining a first heart sound amplitude of the sensed heart sound signal during the first portion of the time interval and a second heart sound amplitude of the sensed heart sound signal during the second portion of the time interval.   
     
     
         17 . The method of  claim 12 , wherein the blood pressure related trigger event comprises a change in posture of the subject. 
     
     
         18 . The method of  claim 12 , wherein the blood pressure related trigger event comprises a change in activity of the subject. 
     
     
         19 . The method of  claim 12 , further comprising producing an indication of when the blood pressure related trigger event has occurred. 
     
     
         20 . The method of  claim 12 , further comprising providing therapy to the subject based on the trend.