Distributed cardiac activity monitoring with selective filtering

Abstract

System and techniques for distributed monitoring of cardiac activity include selective T wave filtering. In general, in one implementation, a distributed cardiac activity monitoring system includes a monitoring apparatus, with a selectively activated T wave filter, and a monitoring station. The monitoring apparatus can include a communications interface, a real-time QRS detector, a T wave filter, and a selector that activates the T wave filter to preprocess a cardiac signal provided to the real-time QRS detector in response to a message. The monitoring station can communicatively couple with the monitoring apparatus, over a communications channel, via the communications interface and can transmit the message to the monitoring apparatus to activate the T wave filter based at least in part upon a predetermined criteria (e.g., abnormal T waves for an individual, as identified by a system operator).

1 . A machine-implemented method comprising: 
 identifying heart beats in a sensed cardiac signal;    activating a T wave filter, used in said identifying heart beats, in response to a message from a monitoring station generated at least in part based upon discovery of a predetermined characteristic in the sensed cardiac signal; and    outputting information corresponding to the identified heart beats to a communications channel of a distributed cardiac activity monitoring system.    
   
   
       2 . The method of  claim 1 , wherein said identifying heart beats comprises identifying R waves in the sensed cardiac signal.  
   
   
       3 . The method of  claim 1 , further comprising sending at least a portion of the sensed cardiac signal to the monitoring station, and wherein the discovery of the predetermined characteristic comprises identification of a tall T wave in the at least a portion of the sensed cardiac signal by an operator at the monitoring station.  
   
   
       4 . The method of  claim 1 , wherein said activating the T wave filter comprises activating a filter that reduces signal amplitude at low frequencies of the sensed cardiac signal.  
   
   
       5 . The method of  claim 4 , wherein the filter has a frequency response of about 0 dB or more at frequencies above ten Hertz.  
   
   
       6 . The method of  claim 5 , wherein the filter has a frequency response of about −10 dB or less in a low frequency range of zero to five Hertz.  
   
   
       7 . The method of  claim 6 , wherein the filter has a frequency response of about +2 dB or more in a high frequency range of twenty to twenty five Hertz.  
   
   
       8 . The method of  claim 1 , wherein said outputting information comprises outputting heart rate data to a wireless communications channel.  
   
   
       9 . The method of  claim 1 , further comprising: 
 determining that an abnormal T wave is possible based on signal morphology analysis; and    notifying a system operator of the possible abnormal T wave.    
   
   
       10 . The method of  claim 1 , further comprising deactivating the T wave filter in response to a second message.  
   
   
       11 . A distributed cardiac activity monitoring system comprising: 
 a monitoring apparatus including a communications interface, a real-time QRS detector, a T wave filter, and a selector that activates the T wave filter with respect to the real-time QRS detector in response to a message, wherein the activated T waver filter preprocesses a cardiac signal provided to the real-time QRS detector; and    a monitoring station that communicatively couples with the monitoring apparatus via the communications interface and transmits the message to the monitoring apparatus to activate the T wave filter based at least in part upon a predetermined criteria.    
   
   
       12 . The system of  claim 11 , wherein the communications interface comprises a wireless communications interface.  
   
   
       13 . The system of  claim 11 , wherein the T wave filter comprises a filter that reduces signal amplitude at low frequencies.  
   
   
       14 . The system of  claim 13 , wherein the filter has a frequency response of about −10 dB or less in a low frequency range of zero to five Hertz.  
   
   
       15 . The system of  claim 13 , wherein the filter has a frequency response of about 0 dB or more at frequencies above ten Hertz.  
   
   
       16 . The system of  claim 15 , wherein the filter has a frequency response of about +2 dB or more in a high frequency range of twenty to twenty five Hertz.  
   
   
       17 . The system of  claim 11 , wherein the selector comprises analog, selective activation circuitry.  
   
   
       18 . The system of  claim 11 , wherein the monitoring apparatus further comprises additional logic that determines if an abnormal T wave is possible based on signal morphology analysis, and notifies a system operator of the possible abnormal T wave.  
   
   
       19 . The system of  claim 11 , wherein the monitoring station further comprises additional logic that determines if an abnormal T wave is possible based on signal morphology analysis, and notifies a system operator of the possible abnormal T wave.  
   
   
       20 . A cardiac monitoring apparatus comprising: 
 a communications interface;    a real-time heart beat detector;    a T wave filter; and    a selector that activates the T wave filter with respect to the real-time heart beat detector in response to a message, wherein the activated T waver filter preprocesses a cardiac signal provided to the real-time heart beat detector.    
   
   
       21 . The apparatus of  claim 20 , wherein the communications interface comprises a wireless communications interface.  
   
   
       22 . The apparatus of  claim 20 , wherein the real-time heart beat detector comprises an analog heart beat detector, the T wave filter comprises an analog T wave filter, and the selector comprises analog, selective activation circuitry.  
   
   
       23 . The apparatus of  claim 20 , wherein the T wave filter comprises a filter that reduces signal amplitude at low frequencies.  
   
   
       24 . The apparatus of  claim 23 , wherein the filter has a frequency response of about −10 dB or less in a low frequency range of zero to five Hertz.  
   
   
       25 . The apparatus of  claim 24 , wherein the filter has a frequency response of about 0 dB or more at frequencies above ten Hertz.  
   
   
       26 . The apparatus of  claim 25 , wherein the filter has a frequency response of about +2 dB or more in a high frequency range of twenty to twenty five Hertz.  
   
   
       27 . The apparatus of  claim 20 , further comprising additional logic that determines if an abnormal T wave is possible based on signal morphology analysis, and notifies a system operator of the possible abnormal T wave.  
   
   
       28 . A method comprising: 
 receiving at least a portion of a sensed cardiac signal from a monitoring apparatus in contact with a living being under active cardiac monitoring;    identify an abnormal T wave in the received cardiac signal; and    sending a message to the monitoring apparatus over a communications channel, the message causing the monitoring apparatus to activate a T wave filter used in identifying heart beats of the living being under active cardiac monitoring.    
   
   
       29 . The method of  claim 28 , further comprising: 
 determining that an abnormal T wave is possible based on signal morphology analysis; and    notifying a system operator of the possible abnormal T wave, wherein the system operator performs said identifying the abnormal T wave.    
   
   
       30 . The method of  claim 28 , wherein said sending the message comprises sending the message over a wireless communications channel.  
   
   
       31 . The method of  claim 28 , further comprising installing the T wave filter into the monitoring apparatus, which comprises a preexisting beat detector.  
   
   
       32 . A system comprising: 
 means for identifying heart beats in a sensed cardiac signal;    means for filtering the sensed cardiac signal to reduce T waves in the sensed cardiac signal; and    means for selectively activating the means for filtering in response to discovery of a predetermined characteristic in the sensed cardiac signal.    
   
   
       33 . The system of  claim 32 , further comprising means for alerting a system operator of a possible abnormal T wave.  
   
   
       34 . The system of  claim 32 , wherein the means for filtering comprises means for generally highpass filtering.