Multiple state morphology-based system detecting ventricular tachycardia and supraventricular tachycardia
First Claim
1. A method, comprising:
- analyzing cardiac signals from an arrhythmic cardiac event using a series of at least two discrimination stages;
in each discrimination stage, classifying the arrhythmic cardiac event as an arrhythmic event that requires therapy or an arrhythmic event that does not require therapy; and
after each discrimination stage, providing therapy if the arrhythmic cardiac event is classified as an event that requires therapy.
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Abstract
A system for detecting ventricular tachycardia and supraventricular tachycardia using a multiple stage morphology based system. Cardiac signals are sensed from a patient'"'"'s heart and analyzed for the occurrence of a tachycardia event. When a tachycardia event is detected, the method and system analyzes a plurality of features of the sensed cardiac signals in two or more discrimination stages. Each of the two or more discrimination stages classify the tachycardia event as either a ventricular tachycardia or a candidate supraventricular tachycardia event. When a discrimination stage detects the occurrence of a ventricular tachycardia, therapy is delivered to the heart to treat the ventricular tachycardia.
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Citations
35 Claims
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1. A method, comprising:
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analyzing cardiac signals from an arrhythmic cardiac event using a series of at least two discrimination stages;
in each discrimination stage, classifying the arrhythmic cardiac event as an arrhythmic event that requires therapy or an arrhythmic event that does not require therapy; and
after each discrimination stage, providing therapy if the arrhythmic cardiac event is classified as an event that requires therapy. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method, comprising:
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applying a first discrimination stage to analyze cardiac signals and determine whether a tachycardia event is either a ventricular tachycardia (VT) event or a candidate supraventricular tachycardia (SVT) event;
providing therapy if the first discrimination stage classifies the tachycardia event as a VT event;
applying a second discrimination stage to analyze cardiac signals and determine whether a tachycardia event is either a VT event or a SVT event; and
providing therapy if the second discrimination stage classifies the tachycardia event as a VT event. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
analyzing a plurality of cardiac complexes;
determining whether each of the analyzed cardiac complexes is a VT complex or a candidate SVT complex;
counting the number of VT complexes and the number of candidate SVT complexes; and
declaring the tachycardia event to be a VT event or a candidate SVT event based on the number of VT complexes and the number of candidate SVT complexes.
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9. The method of claim 8, wherein declaring the tachycardia event to be a VT event or a candidate SVT event based on the number of VT complexes and the number of candidate SVT complexes includes programming a threshold ratio for declaring either a VT event or a candidate SVT event based on the number of VT complexes and the number of candidate SVT complexes.
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10. The method of claim 7, wherein:
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applying a first discrimination stage includes analyzing a first number of signal features;
applying a second discrimination stage includes analyzing a second number of signal features; and
the first number of signal features is less than the second number of signal features such that the first discrimination stage is more efficient than the second stage.
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11. The method of claim 7, wherein applying a first discrimination stage to analyze cardiac signals and determine whether a tachycardia event is either a ventricular tachycardia (VT) event or a candidate supraventricular tachycardia (SVT) event includes:
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comparing an R-wave width of a sensed cardiac complex to a template R-wave width; and
declaring the sensed cardiac complex to be a VT complex when the R-wave width of the sensed cardiac complex is greater than the template R-wave width.
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12. The method of claim 11, wherein the template R-wave width is determined as either an average or a median of R-wave width of cardiac complexes sensed during normal sinus rhythm.
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13. The method of claim 11, wherein the sensed cardiac complex has four features formed by detected major deflection points in the sensed cardiac complex, and the R-wave width of the sensed cardiac complex is determined by the distance between the second and fourth feature.
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14. The method of claim 7, wherein applying a first discrimination stage to analyze cardiac signals and determine whether a tachycardia event is either a ventricular tachycardia (VT) event or a candidate supraventricular tachycardia (SVT) event includes:
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recording the polarity of a largest amplitude feature of a normal cardiac complex sensed during normal sinus rhythm;
detecting a largest amplitude feature of a sensed cardiac complex; and
declaring the sensed cardiac complex to be a VT complex if the polarity of the largest amplitude feature of the sensed cardiac complex is different than the polarity of the large amplitude feature of the normal cardiac complex.
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15. The method of claim 7, wherein:
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applying a first discrimination stage includes performing either an R-wave width discrimination procedure or an R-wave polarity discrimination procedure;
applying a second discrimination stage includes performing either the R-wave width discrimination procedure or the R-wave polarity discrimination procedure, which ever discrimination procedure was not performed in the first discrimination stage;
the R-wave width discrimination procedure includes;
comparing an R-wave width of a sensed cardiac complex to a template R-wave width; and
declaring the sensed cardiac complex to be a VT complex when the R-wave width of the sensed cardiac complex is greater than the template R-wave width; and
the R-wave polarity discrimination procedure includes;
recording the polarity of a largest amplitude feature of a normal cardiac complex sensed during normal sinus rhythm;
detecting a largest amplitude feature of a sensed cardiac complex; and
declaring the sensed cardiac complex to be a VT complex if the polarity of the largest amplitude feature of the sensed cardiac complex is different than the polarity of the large amplitude feature of the normal cardiac complex.
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16. The method of claim 7, wherein:
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applying a first discrimination stage includes performing a first discrimination procedure that includes performing either an R-wave width discrimination procedure or an R-wave polarity discrimination procedure;
applying a second discrimination stage includes performing a second discrimination procedure that analyzes the similarity of a sensed cardiac complex to a normal sinus rhythm template complex;
the R-wave width discrimination procedure includes;
comparing an R-wave width of the sensed cardiac complex to a template R-wave width; and
declaring the sensed cardiac complex to be a VT complex when the R-wave width of the sensed cardiac complex is greater than the template R-wave width; and
the R-wave polarity discrimination procedure includes;
recording the polarity of a largest amplitude feature of a normal cardiac complex sensed during normal sinus rhythm;
detecting a largest amplitude feature of a sensed cardiac complex; and
declaring the tachycardia event to be a VT complex if the polarity of the largest amplitude feature of the sensed cardiac complex is different than the polarity of the large amplitude feature of the normal cardiac complex.
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17. The method of claim 16, wherein performing a second discrimination procedure includes:
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providing a normal feature vector (N) for a normal sinus rhythm complex;
determining a sensed feature vector (A) for a sensed cardiac complex;
determining a similarity value (a∥
) for A by projecting A onto N; and
determining a dissimilarity value (a⊥
) for A based on the determined vector A and the similarity value a∥
.
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18. The method of claim 17, wherein:
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providing a normal feature vector (N) for a normal sinus rhythm complex includes providing a four dimensional normal rhythm vector, N=[N1, N2, N3, N4]; and
determining a sensed feature vector (A) for a sensed cardiac complex includes determining a four dimensional feature vector, A=[A1, A2, A3, A4].
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19. The method of claim 17, wherein determining a similarity value (a∥
- ) for A by projecting A onto N includes performing the calculation;
a∥
=[A·
N]/[N·
N].
- ) for A by projecting A onto N includes performing the calculation;
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20. The method of claim 17, wherein determining a dissimilarity value (a⊥
- ) for A includes performing the calculation;
a⊥
=SQRT[(A·
A)/(N·
N)—
(a∥
)2].
- ) for A includes performing the calculation;
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21. The method of claim 17, wherein:
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the similarity value and dissimilarity value comprise a discrimination point (a∥
, a⊥
);
a similarity/dissimilarity plane is created with normalized vectors N/|N| and A/|N|;
the similarity/dissimilarity plane has orthogonal axes a∥ and
a⊥
;
the similarity/dissimilarity plane has a VT region and a non-VT region, and a boundary that separates the VT region from the non-VT region;
the discrimination point is plotted on the similarity/dissimilarity plane; and
the sensed cardiac complex from which the sensed feature vector A is determined is declared a VT complex if the discrimination point is located in the VT region of the similarity/dissimilarity plane.
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22. The method of claim 21, wherein the sensed cardiac complex from which the sensed feature vector A is determined is declared a SVT complex if the discrimination point is located in the non-VT region of the similarity/dissimilarity plane.
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23. The method of claim 21, wherein the boundary that separates the VT region from the non-VT region is a fixed boundary.
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24. The method of claim 21, wherein the boundary that separates the VT region from the non-VT region is a programmable boundary.
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25. A method, comprising:
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applying a first discrimination stage to analyze cardiac signals and determine whether a tachycardia event is either a ventricular tachycardia (VT) event or a candidate supraventricular tachycardia (SVT) event;
providing therapy if the first discrimination stage classifies the tachycardia event as a VT event;
applying a second discrimination stage to analyze the similarity of a sensed cardiac complex to a normal sinus rhythm complex; and
providing therapy if the second discrimination stage classifies the tachycardia event as a VT event. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
providing a normal feature vector (N) for a normal sinus rhythm complex;
determining a sensed feature vector (A) for a sensed cardiac complex;
determining a similarity value (a∥
) for A by projecting A onto N; and
determining a dissimilarity value (a⊥
) for A based on the determined vector A and the similarity value a∥
.
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27. The method of claim 26, wherein:
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providing a normal feature vector (N) for a normal sinus rhythm complex includes providing a four dimensional normal rhythm vector, N=[N1, N2, N3, N4]; and
determining a sensed feature vector (A) for a sensed cardiac complex includes determining a four dimensional feature vector, A=[A1, A2, A3, A4].
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28. The method of claim 27, wherein determining a similarity value (a∥
- ) for A by projecting A onto N includes performing the calculation;
a∥
=[A·
N]/[N·
N].
- ) for A by projecting A onto N includes performing the calculation;
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29. The method of claim 27, wherein determining a dissimilarity value (a⊥
- ) for A includes performing the calculation;
a⊥
=SQRT[(A·
A)/(N·
N)—
(a∥
)2].
- ) for A includes performing the calculation;
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30. The method of claim 27, wherein:
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the similarity value and dissimilarity value comprise a discrimination point (a∥
, a⊥
);
a similarity/dissimilarity plane is created with normalized vectors N/|N| and A/|N|;
the similarity/dissimilarity plane has orthogonal axes a∥ and
a⊥
;
the similarity/dissimilarity plane has a VT region and a non-VT region, and a boundary that separates the VT region from the non-VT region;
the discrimination point is plotted on the similarity/dissimilarity plane; and
the sensed cardiac complex from which the sensed feature vector A is determined is declared a VT complex if the discrimination point is located in the VT region of the similarity/dissimilarity plane.
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31. The method of claim 30, wherein the sensed cardiac complex from which the sensed feature vector A is determined is declared a SVT complex if the discrimination point is located in the non-VT region of the similarity/dissimilarity plane.
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32. The method of claim 30, wherein the boundary that separates the VT region from the non-VT region is a fixed boundary.
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33. The method of claim 30, wherein the boundary that separates the VT region from the non-VT region is a programmable boundary.
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34. The method of claim 25, wherein applying a first discrimination stage to analyze cardiac signals and determine whether a tachycardia event is either a ventricular tachycardia (VT) event or a candidate supraventricular tachycardia (SVT) event includes:
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comparing an R-wave width of a sensed cardiac complex to a template R-wave width; and
declaring the sensed cardiac complex to be a VT complex when the R-wave width of the sensed cardiac complex is greater than the template R-wave width.
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35. The method of claim 25, wherein applying a first discrimination stage to analyze cardiac signals and determine whether a tachycardia event is either a ventricular tachycardia (VT) event or a candidate supraventricular tachycardia (SVT) event includes:
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recording the polarity of a largest amplitude feature of a normal cardiac complex sensed during normal sinus rhythm;
detecting a largest amplitude feature of a sensed cardiac complex; and
declaring the sensed cardiac complex to be a VT complex if the polarity of the largest amplitude feature of the sensed cardiac complex is different than the polarity of the large amplitude feature of the normal cardiac complex.
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Specification