Method and apparatus for detecting arrhythmias in a subcutaneous medical device

Abstract

A method and apparatus for detecting a cardiac event in a medical device that includes sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector, initiating charging of an energy storage device in response to the sensed cardiac signals, and determining whether a predetermined number of morphologies associated with cardiac signals sensed along the first sensing vector and the second sensing vector during corresponding sensing windows are indicative of the cardiac event.

We claim: 
     
         1 . A method of detecting a cardiac event in a medical device, comprising:
 sensing cardiac signals from a plurality of electrodes;   initiating charging of an energy storage device in response to the sensed cardiac signals; and   determining, during charging of the energy storage device, whether a morphology of a signal associated with cardiac signals sensed during a sensing window is indicative of the cardiac event.   
     
     
         2 . The method of  claim 1 , wherein the plurality of electrodes are positioned non-transvenously. 
     
     
         3 . The method of  claim 1 , further comprising:
 determining, in response to the morphology being indicative of the cardiac event, whether the charging of the energy storage device is completed; and   determining, in response to the charging of the energy storage device being completed, whether the cardiac event is confirmed in response to morphologies of cardiac signals sensed during a first plurality of sensing windows.   
     
     
         4 . The method of  claim 3 , further comprising determining, in response to the cardiac event not being confirmed, whether morphologies of cardiac signals sensed during a second plurality of sensing windows are indicative of the cardiac event. 
     
     
         5 . The method of  claim 1 , further comprising:
 aborting the charging of the energy storage device in response to morphologies of cardiac signals sensed during a predetermined number of a first plurality of sensing windows not corresponding to the cardiac event; and   determining, in response to subsequent cardiac signals sensed during a second plurality of sensing windows, whether morphologies of cardiac signals sensed during the second plurality of sensing windows are indicative of the cardiac event.   
     
     
         6 . The method of  claim 1 , wherein the sensing window is between approximately 0.5 and 10 seconds. 
     
     
         7 . A method of detecting a cardiac event in a medical device, comprising:
 sensing cardiac signals from a plurality of electrodes, the plurality of electrodes forming a first sensing vector and a second sensing vector;   initiating charging of an energy storage device in response to the sensed cardiac signals; and   determining whether a predetermined number of morphologies associated with cardiac signals sensed along the first sensing vector and the second sensing vector during corresponding sensing windows are indicative of the cardiac event.   
     
     
         8 . The method of  claim 7 , wherein the plurality of electrodes are positioned non-transvenously. 
     
     
         9 . The method of  claim 7 , wherein the determining comprises determining whether the sensed cardiac signal associated with the most recent two sensing windows for both the first sensing vector and the second sensing vector is indicative of the cardiac event. 
     
     
         10 . The method of  claim 7 , further comprising:
 determining whether the charging of the energy storage device is completed; and   determining, in response to the charging of the energy storage device being completed, whether the cardiac event is confirmed in response to a cardiac signal sensed along the first sensing vector and the second sensing vector during a plurality of sensing windows.   
     
     
         11 . The method of  claim 10 , wherein the cardiac event is confirmed in response to the cardiac signal sensed along both the first sensing vector and the second sensing vector during at least five of the last eight sensing windows and at least two of the last three sensing windows of the plurality of sensing windows corresponding to the cardiac event. 
     
     
         12 . The method of  claim 11 , wherein determining whether the cardiac event is confirmed further comprises determining whether a cardiac signal sensed during a most recent sensing window of the plurality of sensing windows corresponds to the cardiac event for at least one of the first sensing vector and the second sensing vector. 
     
     
         13 . The method of  claim 10 , further comprising determining, in response to the cardiac event not being confirmed, whether state transition requirements are satisfied, the state transition requirements corresponding to whether the cardiac signal sensed during two of the last three sensing windows, three of the last eight sensing windows, and the most recent sensing window of the plurality of sensing windows correspond to the cardiac event along both the first sensing vector and the second sensing vector. 
     
     
         14 . The method of  claim 13 , further comprising determining, in response to the state transition requirements being satisfied, whether redetection requirements associated with cardiac signals sensed during sensing windows of the plurality of sensing windows are satisfied for both the first sensing vector and the second sensing vector. 
     
     
         15 . The method of  claim 14 , wherein the redetection requirements correspond to determining whether the cardiac signal sensed during two of the last three sensing windows of the plurality of sensing windows correspond to the cardiac event for both the first sensing vector and the second sensing vector. 
     
     
         16 . The method of  claim 7 , further comprising:
 aborting the charging of the energy storage device in response to cardiac signals sensed during a predetermined number of a plurality of the sensing windows not corresponding to the cardiac event; and   determining, in response to cardiac signals sensed during sensing windows of the plurality of sensing windows, whether state transition requirements are satisfied.   
     
     
         17 . The method of  claim 16 , wherein the state transition requirements correspond to determining whether the cardiac signal sensed during two of the last three sensing windows, three of the last eight sensing windows, and the most recent sensing window of the plurality of sensing windows correspond to the cardiac event for both the first sensing vector and the second sensing vector. 
     
     
         18 . The method of  claim 7 , wherein the sensing window is between approximately 0.5 and 10 seconds. 
     
     
         19 . A medical device for detecting a cardiac event and delivering a corresponding therapy, the device comprising:
 a plurality of electrodes sensing cardiac signals, the plurality of electrodes forming a first sensing vector and a second sensing vector;   an energy storage device; and   a control unit to determine whether a predetermined number of morphologies associated with cardiac signals sensed along the first sensing vector and the second sensing vector during corresponding sensing windows are indicative of the cardiac event and initiating charging of the energy storage device in response to the cardiac event being indicated.   
     
     
         20 . The device of  claim 19 , wherein the plurality of electrodes are positioned non-transvenously.