Methods and apparatus for discriminating polymorphic tachyarrhythmias from monomorphic tachyarrhythmias facilitating detection of fibrillation
First Claim
1. In an implantable medical device that detects a polymorphic tachyarrhythmia of the heart of a patient as a function of measured time intervals between sensed events in a cardiac signal, a method of improving the specificity of discriminating between a monomorphic tachyarrhythmia and a polymorphic tachyarrhythmia comprising the steps of:
- a) provisionally declaring a polymorphic tachyarrhythmia when at least a first number of the measured time intervals satisfy the polymorphic tachyarrhythmia detection criteria;
b) successively sampling, processing, and temporarily storing the cardiac signals to derive a plurality y of data sets of signal amplitudes;
c) successively deriving a plurality y of sets of wavelet transform coefficients from the respective plurality y of data sets of signal amplitudes;
d) comparing at least selected ones of the wavelet transform coefficients of each of the y sets of wavelet transform coefficients to determine a match count x of the y sets of wavelet transform coefficients that match one another within at least a predetermined match tolerance;
e) withholding the final declaration of a polymorphic tachyarrhythmia if the match count x indicates that the corresponding cardiac signals exhibit morphologic stability suggestive of a monomorphic tachyarrhythmia; and
f) making the final declaration of a polymorphic tachyarrhythmia if the match count x indicates that the corresponding cardiac signals exhibit morphological instability suggestive of a polymorphic tachyarrhythmia and the polymorphic tachyarrhythmia is provisionally declared in step a).
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Abstract
Methods and apparatus are provided for discriminating high rate polymorphic QRS complexes from high rate monomorphic QRS complexes to increase the specificity of detection of polymorphic VT and VF employing wavelet transform signal processing of the QRS complexes are disclosed. Wavelet transforms are applied to the sampled amplitude values of a sequence of QRS complexes to develop wavelet transform coefficient (WTC) data sets. At least selected ones of the WTC data sets are processed and comparisons are made to determine a wavelet match score. A determination is made as a function of the wavelet match scores of the series of successive QRS complexes that characterizes the most recent QRS complex as more or less likely to signify polymorphic VT or VF.
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Citations
42 Claims
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1. In an implantable medical device that detects a polymorphic tachyarrhythmia of the heart of a patient as a function of measured time intervals between sensed events in a cardiac signal, a method of improving the specificity of discriminating between a monomorphic tachyarrhythmia and a polymorphic tachyarrhythmia comprising the steps of:
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a) provisionally declaring a polymorphic tachyarrhythmia when at least a first number of the measured time intervals satisfy the polymorphic tachyarrhythmia detection criteria; b) successively sampling, processing, and temporarily storing the cardiac signals to derive a plurality y of data sets of signal amplitudes; c) successively deriving a plurality y of sets of wavelet transform coefficients from the respective plurality y of data sets of signal amplitudes; d) comparing at least selected ones of the wavelet transform coefficients of each of the y sets of wavelet transform coefficients to determine a match count x of the y sets of wavelet transform coefficients that match one another within at least a predetermined match tolerance; e) withholding the final declaration of a polymorphic tachyarrhythmia if the match count x indicates that the corresponding cardiac signals exhibit morphologic stability suggestive of a monomorphic tachyarrhythmia; and f) making the final declaration of a polymorphic tachyarrhythmia if the match count x indicates that the corresponding cardiac signals exhibit morphological instability suggestive of a polymorphic tachyarrhythmia and the polymorphic tachyarrhythmia is provisionally declared in step a). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. In an implantable medical device that provisionally detects a polymorphic tachyarrhythmia of the heart of a patient as a function of measured time intervals between sensed events in a cardiac signal, a system of improving the specificity of discriminating between a monomorphic tachyarrhythmia and a polymorphic tachyarrhythmia comprising:
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provisional declaring means for provisionally declaring a polymorphic tachyarrhythmia when at least a first number of the measured time intervals satisfy the polymorphic tachyarrhythmia detection criteria; signal processing means for successively sampling, processing, and temporarily storing the cardiac signals to derive a plurality y of data sets of signal amplitudes; wavelet transform means for successively deriving a plurality y of sets of wavelet transform coefficients from the respective plurality y of data sets of signal amplitudes; comparing means for comparing at least selected ones of the wavelet transform coefficients of each of the y sets of wavelet transform coefficients to determine a match count x of the y sets of wavelet transform coefficients that match one another within at least a predetermined match tolerance; withholding means for withholding the final declaration of a polymorphic tachyarrhythmia if the match count x indicates that the corresponding cardiac signals exhibit morphologic stability suggestive of a monomorphic tachyarrhythmia; and final declaring means for making the final declaration of a polymorphic tachyarrhythmia if the match count x indicates that the corresponding cardiac signals exhibit morphological instability suggestive of a polymorphic tachyarrhythmia and the polymorphic tachyarrhythmia is provisionally declared. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification