Systems and methods for employing an FFT to distinguish R-waves from T-waves using an implantable medical device
First Claim
1. A method for use by an implantable medical device for implant within a patient for distinguishing cardiac events sensed by the device, said method comprising:
- sensing time-varying electrical cardiac signals within the patient using the device;
identifying time-varying ventricular electrical cardiac event waveforms therein using the device;
determining an initial ventricular rate based on all ventricular event waveforms detected within the time-varying signal;
detecting a possible ventricular tachyarrhythmia within the patient based on a ventricular rate derived from all ventricular events within the time-varying signal by comparing the initial ventricular rate against upper and lower ventricular fibrillation (VF) thresholds;
if the initial ventricular rate is between the upper and lower VF thresholds, converting the time-varying event waveforms using the device into frequency-domain waveforms to detect spectral components of the events; and
distinguishing different types of ventricular cardiac events corresponding to individual heartbeats based on the spectral components of the events.
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Abstract
A Fast Fourier Transform (FFT) converts time-varying event waveforms into the frequency domain waveforms to thereby decompose the events into their spectral components, which are analyzed to distinguish R-waves from T-waves. In some embodiments, the FFT is only activated if a ventricular tachyarrhythmia is already indicated. For example, an initial ventricular rate may be derived from a ventricular IEGM based on all events detected therein. The initial ventricular rate is compared against one or more thresholds representative of ventricular tachycardia (VT) and/or ventricular fibrillation (VF) to determine if VT/VF is indicated. If so, the FFT is activated to distinguish R-waves from T-waves and, in particular, to detect and eliminate T-wave oversensing. Then, the ventricular rate is re-determined based only on the rate of true R-waves. Therapy is delivered if VT/VF is still detected.
60 Citations
26 Claims
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1. A method for use by an implantable medical device for implant within a patient for distinguishing cardiac events sensed by the device, said method comprising:
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sensing time-varying electrical cardiac signals within the patient using the device; identifying time-varying ventricular electrical cardiac event waveforms therein using the device; determining an initial ventricular rate based on all ventricular event waveforms detected within the time-varying signal; detecting a possible ventricular tachyarrhythmia within the patient based on a ventricular rate derived from all ventricular events within the time-varying signal by comparing the initial ventricular rate against upper and lower ventricular fibrillation (VF) thresholds; if the initial ventricular rate is between the upper and lower VF thresholds, converting the time-varying event waveforms using the device into frequency-domain waveforms to detect spectral components of the events; and
distinguishing different types of ventricular cardiac events corresponding to individual heartbeats based on the spectral components of the events. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for use by an implantable medical device for implant within a patient for distinguishing cardiac events sensed by the device, said method comprising:
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sensing time-varying electrical cardiac signals within the patient using the device; identifying time-varying ventricular electrical cardiac event waveforms therein using the device; converting the time-varying event waveforms using the device into frequency-domain waveforms to detect spectral components of the events; distinguishing different types of ventricular cardiac events corresponding to individual heartbeats based on the spectral components of the events to distinguish ventricular depolarization events (R-waves) from ventricular repolarization events (T-waves); detecting a quiescent period within the patient; detecting depolarization events (R-waves) and repolarization events (T-waves) within the quiescent period and power values associated therewith; and determining suitable comparison values based on characteristics of the depolarization events (R-waves) and repolarization events (T-waves) within the quiescent period and their power values.
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20. A method for use by an implantable medical device for implant within a patient for distinguishing cardiac events sensed by the device, said method comprising:
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sensing time-varying electrical cardiac signals within the patient using the device; identifying time-varying ventricular electrical cardiac event waveforms therein using the device; converting the time-varying event waveforms using the device into frequency-domain waveforms to detect spectral components of the events; distinguishing different types of ventricular cardiac events corresponding to individual heartbeats based on the spectral components of the events to distinguish ventricular depolarization events (R-waves) from ventricular repolarization events (T-waves); and detecting the oversensing of ventricular repolarization events (T-waves) within a cardiac signal. - View Dependent Claims (21)
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22. An implantable medical device for implant within a patient, said device comprising:
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a cardiac signal sensing system operative to sense time-varying electrical cardiac signals within the patient; an event identification unit operative to identifying time-varying ventricular electrical cardiac event waveforms within the sensed signals; a spectral component detection unit operative to convert the time-varying event waveforms into frequency-domain waveforms to detect spectral components of the events; a spectral component-based discriminator operative to distinguish ventricular depolarization events (R-waves) from ventricular repolarization events (T-waves) based on the spectral components of the events; and an oversensing detection unit operative to detect the oversensing of ventricular repolarization events (T-waves) within the cardiac signals. - View Dependent Claims (23, 24, 25)
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26. A method for use by an implantable medical device for implant within a patient for distinguishing cardiac events sensed by the device, said method comprising:
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sensing time-varying electrical cardiac signals within the patient using the device; identifying time-varying ventricular electrical cardiac event waveforms therein; converting the time-varying event waveforms into frequency-domain waveforms to detect spectral components of the events; distinguishing ventricular depolarization events (R-waves) from ventricular repolarization events (T-waves) based on the spectral components of the events; and detecting the oversensing of ventricular repolarization events (T-waves) within the cardiac signals following the distinguishing of ventricular depolarization events (R-waves) from ventricular repolarization events (T-waves).
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Specification