Method and apparatus for detecting arrhythmias in a subcutaneous medical device

Abstract

A method and system for use with an implantable medical device for subcutaneous implant within a patient to determine a likelihood of the patient experiencing a cardiac event that includes sensing a cardiac signal along a plurality of different sensing vectors, determining state information of each vector of the plurality of sensing vectors, determining a cross correlation of the determined state information of each vector of the plurality of sensing vectors, comparing the cross correlation of the determined state information of each vector of the plurality of sensing vectors to a threshold, and detecting the cardiac event in response to the comparing.

We claim: 
     
         1 . A method of determining a likelihood of an occurrence of a cardiac event in a subcutaneously implanted medical device, comprising
 sensing a cardiac signal along a plurality of different sensing vectors;   determining state information of each vector of the plurality of sensing vectors;   determining a cross correlation of the determined state information of each vector of the plurality of sensing vectors;   comparing the cross correlation of the determined state information of each vector of the plurality of sensing vectors to a threshold; and   detecting the cardiac event in response to the comparing.   
     
     
         2 . The method of  claim 1 , wherein determining state information of each vector of the plurality of sensing vectors comprises identifying each vector of the plurality of sensing vectors as being one of shockable and not shockable. 
     
     
         3 . The method of  claim 2 , wherein the plurality of different sensing vectors comprises a first sensing vector and a second sensing vector, and determining a cross correlation of the determined state information of each vector of the plurality of sensing vectors to a threshold comprises determining whether both the first sensing vector and the second sensing vector are identified as being shockable, whether both the first sensing vector and the second sensing vector are identified as being not shockable, or whether one of the first sensing vector and the second sensing vector is identified as being shockable and the other of the first sensing vector and the second sensing vector is identified as being not shockable. 
     
     
         4 . The method of  claim 2 , further comprising;
 determining whether each vector of the plurality of vectors is corrupted by noise;   identifying each vector of the plurality of vectors as being not shockable in response to each vector of the plurality of vectors being corrupted by noise; and   determining, in response to each vector of the plurality of vectors not being corrupted by noise, whether only one vector of the plurality of vectors is corrupted by noise.   
     
     
         5 . The method of  claim 4 , further comprising:
 determining, in response to only one vector of the plurality of vectors being corrupted by noise, whether a vector of the plurality of vectors determined not to be corrupted by noise comprises regular RR intervals;   determining whether the vector of the plurality of vectors determined not to be corrupted by noise is within a first shock zone in response to determining the vector of the plurality of vectors determined not to be corrupted by noise comprises regular RR intervals; and   determining whether the vector of the plurality of vectors determined not to be corrupted by noise is within a second shock zone, different from the first shock zone, in response to determining the vector of the plurality of vectors determined not to be corrupted by noise does not comprise regular RR intervals.   
     
     
         6 . The method of  claim 5 , wherein the first shock zone comprises a ventricular tachycardia shock zone and the second shock zone comprises a ventricular fibrillation shock zone. 
     
     
         7 . The method of  claim 5 , further comprising:
 identifying, in response to the vector of the plurality of vectors determined not to be corrupted by noise being within the first shock zone, each vector of the plurality of vectors as being shockable; and   identifying, in response to the vector of the plurality of vectors determined not to be corrupted by noise not being within the first shock zone, each vector of the plurality of vectors as being not shockable.   
     
     
         8 . The method of  claim 5 , further comprising identifying, in response to the vector of the plurality of vectors determined not to be corrupted by noise not being within the second shock zone, each vector of the plurality of vectors as being not shockable. 
     
     
         9 . The method of  claim 8 , further comprising:
 determining, in response to the vector of the plurality of vectors determined not to be corrupted by noise being within the second shock zone, whether a vector of the plurality of vectors determined to be corrupted by noise is within the second shock zone; and   identifying, in response to the vector of the plurality of vectors determined to be corrupted by noise being within the second shock zone, each vector of the plurality of vectors as being shockable.   
     
     
         10 . The method of  claim 8 , further comprising:
 determining, in response to the vector of the plurality of vectors determined not to be corrupted by noise being within the second shock zone, whether a vector of the plurality of vectors determined to be corrupted by noise is within the second shock zone; and   identifying, in response to the vector of the plurality of vectors determined to be corrupted by noise not being within the second shock zone, the vector of the plurality of vectors determined not to be corrupted by noise as being shockable, and the vector of the plurality of vectors determined to be corrupted by noise as being not shockable.   
     
     
         11 . The method of  claim 4 , further comprising:
 determining, in response to each vector of the plurality of vectors being corrupted by noise, whether each vector of the plurality of vectors comprises regular RR intervals;   determining, in response to each vector of the plurality of vectors comprising regular RR intervals, whether the cardiac signal is within a first shock; and   determining, in response to each vector of the plurality of vectors not comprising regular RR intervals, whether each vector of the plurality of vectors is within a second shock zone different from the first shock zone.   
     
     
         12 . The method of  claim 11 , wherein the first shock zone comprises a ventricular tachycardia shock zone and the second shock zone comprises a ventricular fibrillation shock zone. 
     
     
         13 . A system for use with an implantable medical device for subcutaneous implant within a patient to determine a likelihood of the patient experiencing a cardiac event, comprising:
 a plurality of electrodes   a sensing module couple to the plurality of electrodes sensing a cardiac signal along a plurality of different sensing vectors formed by electrodes of the plurality of electrodes; and   a processor configured to determine state information of each vector of the plurality of different sensing vectors, determine a cross correlation of the determined state information of each vector of the plurality of sensing vectors, compare the cross correlation of the determined state information of each vector of the plurality of sensing vectors to a threshold, and detect heart failure in response to the comparing.   
     
     
         14 . The system of  claim 13 , wherein determining state information of each vector of the plurality of sensing vectors comprises identifying each vector of the plurality of sensing vectors as being one of shockable and not shockable. 
     
     
         15 . The system of  claim 14 , wherein the plurality of different sensing vectors comprises a first sensing vector and a second sensing vector, and determining a cross correlation of the determined state information of each vector of the plurality of sensing vectors to a threshold comprises determining whether both the first sensing vector and the second sensing vector are identified as being shockable, whether both the first sensing vector and the second sensing vector are identified as being not shockable, or whether one of the first sensing vector and the second sensing vector is identified as being shockable and the other of the first sensing vector and the second sensing vector is identified as being not shockable. 
     
     
         16 . The system of  claim 14 , wherein the processor is configured to determine whether each vector of the plurality of vectors is corrupted by noise, identify each vector of the plurality of vectors as being not shockable in response to each vector of the plurality of vectors being corrupted by noise, and determine, in response to each vector of the plurality of vectors not being corrupted by noise, whether only one vector of the plurality of vectors is corrupted by noise. 
     
     
         17 . The system of  claim 16 , wherein the processor is configured to determine, in response to only one vector of the plurality of vectors being corrupted by noise, whether a vector of the plurality of vectors determined not to be corrupted by noise comprises regular RR intervals, determine whether the vector of the plurality of vectors determined not to be corrupted by noise is within a first shock zone in response to determining the vector of the plurality of vectors determined not to be corrupted by noise comprises regular RR intervals, and determine whether the vector of the plurality of vectors determined not to be corrupted by noise is within a second shock zone, different from the first shock zone, in response to determining the vector of the plurality of vectors determined not to be corrupted by noise does not comprise regular RR intervals. 
     
     
         18 . The system of  claim 17 , wherein the first shock zone comprises a ventricular tachycardia shock zone and the second shock zone comprises a ventricular fibrillation shock zone. 
     
     
         19 . The system of  claim 17 , wherein the processor is configured to identify, in response to the vector of the plurality of vectors determined not to be corrupted by noise being within the first shock zone, each vector of the plurality of vectors as being shockable, and identify, in response to the vector of the plurality of vectors determined not to be corrupted by noise not being within the first shock zone, each vector of the plurality of vectors as being not shockable. 
     
     
         20 . The system of  claim 17 , wherein the processor is configured to identify, in response to the vector of the plurality of vectors determined not to be corrupted by noise not being within the second shock zone, each vector of the plurality of vectors as being not shockable. 
     
     
         21 . The system of  claim 20 , wherein the processor is configured to determine, in response to the vector of the plurality of vectors determined not to be corrupted by noise being within the second shock zone, whether a vector of the plurality of vectors determined to be corrupted by noise is within the second shock zone, and identify, in response to the vector of the plurality of vectors determined to be corrupted by noise being within the second shock zone, each vector of the plurality of vectors as being shockable. 
     
     
         22 . The system of  claim 20 , wherein the processor is configured to determine, in response to the vector of the plurality of vectors determined not to be corrupted by noise being within the second shock zone, whether a vector of the plurality of vectors determined to be corrupted by noise is within the second shock zone, and identify, in response to the vector of the plurality of vectors determined to be corrupted by noise not being within the second shock zone, the vector of the plurality of vectors determined not to be corrupted by noise as being shockable, and the vector of the plurality of vectors determined to be corrupted by noise as being not shockable. 
     
     
         23 . The system of  claim 16 , wherein the processor is configured to determine, in response to each vector of the plurality of vectors being corrupted by noise, whether each vector of the plurality of vectors comprises regular RR intervals, determine, in response to each vector of the plurality of vectors comprising regular RR intervals, whether the cardiac signal is within a first shock, and determine, in response to each vector of the plurality of vectors not comprising regular RR intervals, whether each vector of the plurality of vectors is within a second shock zone different from the first shock zone. 
     
     
         24 . The system of  claim 23 , wherein the first shock zone comprises a ventricular tachycardia shock zone and the second shock zone comprises a ventricular fibrillation shock zone. 
     
     
         25 . A computer-readable medium storing a set of instructions which cause a processor of a subcutaneous implantable medical device to perform a method of determining a likelihood of an occurrence of a cardiac event, the method comprising:
 sensing a cardiac signal along a plurality of different sensing vectors;   determining state information of each vector of the plurality of sensing vectors;   determining a cross correlation of the determined state information of each vector of the plurality of sensing vectors;   comparing the cross correlation of the determined state information of each vector of the plurality of sensing vectors to a threshold; and   detecting the cardiac event in response to the comparing.   
     
     
         26 . The computer-readable medium of  claim 25 , wherein determining state information of each vector of the plurality of sensing vectors comprises identifying each vector of the plurality of sensing vectors as being one of shockable and not shockable. 
     
     
         27 . The computer-readable medium of  claim 2 , wherein the plurality of different sensing vectors comprises a first sensing vector and a second sensing vector, and determining a cross correlation of the determined state information of each vector of the plurality of sensing vectors to a threshold comprises determining whether both the first sensing vector and the second sensing vector are identified as being shockable, whether both the first sensing vector and the second sensing vector are identified as being not shockable, or whether one of the first sensing vector and the second sensing vector is identified as being shockable and the other of the first sensing vector and the second sensing vector is identified as being not shockable.