Intracardiac impedance and its applications
First Claim
1. A system comprising:
- a medical device including;
a cardiac cycle sensing circuit, the sensing circuit configured to provide a sensed cardiac cycle;
an impedance measurement circuit configured to provide an intracardiac impedance signal; and
a controller circuit coupled to the impedance measurement circuit, the controller circuit configured to detect tachyarrhythmia from the intracardiac impedance signal using at least two of;
a cardiac-cycle-to-cardiac-cycle change in a value of a baseline intracardiac impedance value calculated, for a particular cardiac cycle, to represent the baseline intracardiac impedance for that particular cardiac cycle;
a cardiac-cycle-to-cardiac-cycle change in a value of maximum intracardiac impedance value calculated, for a particular cardiac cycle, to represent the maximum intracardiac impedance for that particular cardiac cycle; and
a cardiac-cycle-to-cardiac-cycle change in a slope value of the intracardiac impedance waveform signal, for a particular cardiac cycle, the slope value measured at a time corresponding to one-half of a time interval over which a maximum intracardiac impedance change occurs during that particular cardiac cycle.
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Accused Products
Abstract
A system to measure intracardiac impedance includes implantable electrodes and a medical device. The electrodes sense electrical signals of a heart of a subject. The medical device includes a cardiac signal sensing circuit coupled to the implantable electrodes, an impedance measurement circuit coupled to the same or different implantable electrodes, and a controller circuit coupled to the cardiac signal sensing circuit and the impedance measurement circuit. The cardiac signal sensing circuit provides a sensed cardiac signal. The impedance measurement circuit senses intracardiac impedance between the electrodes to obtain an intracardiac impedance signal. The controller circuit determines cardiac cycles of the subject using the sensed cardiac signal, and detects tachyarrhythmia using cardiac-cycle to cardiac-cycle changes in a plurality of intracardiac impedance parameters obtained from the intracardiac impedance signal.
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Citations
28 Claims
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1. A system comprising:
a medical device including; a cardiac cycle sensing circuit, the sensing circuit configured to provide a sensed cardiac cycle; an impedance measurement circuit configured to provide an intracardiac impedance signal; and a controller circuit coupled to the impedance measurement circuit, the controller circuit configured to detect tachyarrhythmia from the intracardiac impedance signal using at least two of; a cardiac-cycle-to-cardiac-cycle change in a value of a baseline intracardiac impedance value calculated, for a particular cardiac cycle, to represent the baseline intracardiac impedance for that particular cardiac cycle; a cardiac-cycle-to-cardiac-cycle change in a value of maximum intracardiac impedance value calculated, for a particular cardiac cycle, to represent the maximum intracardiac impedance for that particular cardiac cycle; and a cardiac-cycle-to-cardiac-cycle change in a slope value of the intracardiac impedance waveform signal, for a particular cardiac cycle, the slope value measured at a time corresponding to one-half of a time interval over which a maximum intracardiac impedance change occurs during that particular cardiac cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method comprising:
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sensing cardiac cycles of a patient; sensing intracardiac impedance to obtain an intracardiac impedance waveform; measuring intracardiac impedance parameters from the waveform including at least two of; a cardiac-cycle-to-cardiac-cycle change in a value of a baseline intracardiac impedance value calculated, for a particular cardiac cycle, to represent the baseline intracardiac impedance for that particular cardiac cycle; a cardiac-cycle-to-cardiac-cycle change in a value of maximum intracardiac impedance value calculated, for a particular cardiac cycle, to represent the maximum intracardiac impedance value for that particular cardiac cycle; and a cardiac-cycle-to-cardiac-cycle change in a slope value of an intracardiac impedance waveform signal, for a particular cardiac cycle, the slope value measured at a time corresponding to one-half of a time interval over which a maximum intracardiac impedance change occurs during the particular cardiac cycle; and detecting tachyarrhythmia using at least one change in the intracardiac impedance parameters. - View Dependent Claims (13, 14, 15)
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16. A method comprising:
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sensing electrical cardiac signals of a subject; detecting tachyarrhythmia and determining whether the tachyarrhythmia is ventricular tachycardia or ventricular fibrillation, or supraventricular tachycardia using the electrical cardiac signals; sensing an intracardiac impedance signal during the tachyarrhythmia; determining whether the tachyarrhythmia is stable using intracardiac impedance parameters derived from the intracardiac impedance signal wherein the intracardiac impedance parameters include at least two of; a cardiac-cycle-to-cardiac-cycle change in a value of a baseline intracardiac impedance value calculated, for a particular cardiac cycle, to represent the baseline intracardiac impedance for that particular cardiac cycle; a cardiac-cycle-to-cardiac-cycle change in a value of maximum intracardiac impedance value calculated, for a particular cardiac cycle, to represent the maximum intracardiac impedance for that particular cardiac cycle; and a cardiac-cycle-to-cardiac-cycle change in a value of a slope of the intracardiac impedance waveform signal, for a particular cardiac cycle, the slope value measured at a time corresponding to one-half of a time interval over which a maximum intracardiac impedance change occurs during that particular cardiac cycle; and providing a shock therapy to the subject if the tachyarrhythmia is ventricular tachycardia or fibrillation and is unstable, and providing anti-tachycardia pacing (ATP) therapy to the subject if the tachyarrhythmia is ventricular tachycardia or fibrillation and is stable. - View Dependent Claims (18)
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17. The method of 16, wherein providing ATP therapy to the subject if the tachyarrhythmia is ventricular tachycardia or fibrillation and stable includes providing ATP therapy before resorting to shock therapy if ATP does not mitigate the tachyarrhythmia.
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19. The method of 16, wherein determining whether the tachyarrhythmia is stable using the intracardiac impedance signal includes measuring the intracardiac impedance parameters from a sensed intracardiac impedance signal waveform in association with cardiac cycles.
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20. The method of 16, wherein sensing the electrical cardiac signals and sensing the intracardiac impedance signal includes sensing using an IMD, and wherein providing a shock therapy includes providing shock therapy using an IMD.
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21. A method comprising:
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sensing cardiac cycles of a patient; sensing intracardiac impedance using an IMD to obtain an intracardiac impedance waveform; measuring intracardiac impedance parameters from the waveform including at least two of; a cardiac-cycle-to-cardiac-cycle change in a value of a baseline intracardiac impedance value calculated, for a particular cardiac cycle, to represent the baseline intracardiac impedance for that particular cardiac cycle; a cardiac-cycle-to-cardiac-cycle change in a value of maximum intracardiac impedance value calculated, for a particular cardiac cycle, to represent the maximum intracardiac impedance for that particular cardiac cycle; and a cardiac-cycle-to-cardiac-cycle change in a value of a slope of the intracardiac impedance waveform signal, for a particular cardiac cycle, the slope value measured at a time corresponding to one-half of a time interval over which a maximum intracardiac impedance change occurs during the particular cardiac cycle; and deeming that a cardiac decompensation event occurred using at least one change in the intracardiac impedance parameters. - View Dependent Claims (22, 23, 24, 25)
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26. A method comprising:
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sensing cardiac cycles of a patient using an implantable medical device (IMD); sensing intracardiac impedance using the IMD to obtain an intracardiac impedance waveform; measuring intracardiac impedance parameters from the waveform including at least two of; a cardiac-cycle-to-cardiac-cycle change in a value of a baseline intracardiac impedance value calculated, for a particular cardiac cycle, to represent the baseline intracardiac impedance for that particular cardiac cycle; a cardiac-cycle-to-cardiac-cycle change in a value of maximum intracardiac impedance value calculated, for a particular cardiac cycle, to represent the maximum intracardiac impedance for that particular cardiac cycle; and a cardiac-cycle-to-cardiac-cycle change in a value of a slope of the intracardiac impedance waveform signal, for a particular cardiac cycle, the slope value measured at a time corresponding to one-half of a time interval over which a maximum intracardiac impedance change occurs during the particular cardiac cycle; and trending changes in the plurality of intracardiac impedance parameters, wherein the changes are measured between multiple cardiac cycles. - View Dependent Claims (27, 28)
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Specification