Rate responsive pacing system with QT sensor based on intrinsic QT data
First Claim
1. A rate responsive pacing system having a pacemaker device and a lead system interconnecting said device and a patient'"'"'s heart, said device having a pulse generator for generating pacing pulses, sensing means for sensing cardiac signals connected from said pulse generator to deliver pacing pulses at said sensor rate, said sensor means comprising:
- algorithm means for calculating a measure of the T wave portion of a received intrinsic cardiac signal;
comparing means for comparing said measure with a predetermined criterion to detect the occurrence of the T wave portion of said signal;
data means for determining and storing intrinsic QT interval data and heart rate data for each received intrinsic signal for which a T wave has been detected; and
reference means for setting a QT reference curve as a function of said stored intrinsic QT interval and rate data, wherein said sensor means comprises high rate limit means for setting a maximum sensor rate, and wherein said algorithm means, said comparing means and said state means are operative at rates above said maximum sensor rate.
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Accused Products
Abstract
There is provided a system and method of rate responsive pacing, having an intrinsic QT rate sensor. The system has the capability of sensing the QT interval of intrinsic cardiac signals and constructing from such intrinsic QT data a QT reference curve. The QT reference curve is used for comparison with beat-to-beat QT interval data, in order to provide sensor information for controlling pacing rate. The system of this invention preferably utilizes DSP circuitry for determining the occurrence of a Twave event and the timing of the Twave, from which the QT interval is calculated. The system also provides for compensation of any QT interval which is calculated following ventricular pacing, so that the QT sensor is operative at all times and throughout the entire rate range experienced by the patient. The system thereby provides an enhanced QT rate responsive pacing arrangement, and avoids the need of overdrive pacing in order to obtain QT reference data.
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Citations
34 Claims
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1. A rate responsive pacing system having a pacemaker device and a lead system interconnecting said device and a patient'"'"'s heart, said device having a pulse generator for generating pacing pulses, sensing means for sensing cardiac signals connected from said pulse generator to deliver pacing pulses at said sensor rate, said sensor means comprising:
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algorithm means for calculating a measure of the T wave portion of a received intrinsic cardiac signal;
comparing means for comparing said measure with a predetermined criterion to detect the occurrence of the T wave portion of said signal;
data means for determining and storing intrinsic QT interval data and heart rate data for each received intrinsic signal for which a T wave has been detected; and
reference means for setting a QT reference curve as a function of said stored intrinsic QT interval and rate data, wherein said sensor means comprises high rate limit means for setting a maximum sensor rate, and wherein said algorithm means, said comparing means and said state means are operative at rates above said maximum sensor rate. - View Dependent Claims (2, 3, 4)
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5. A rate responsive pacing system having a pacemaker device and a lead system interconnecting said device and a patient'"'"'s heart, said device having a pulse generator for generating pacing pulses, sensing means for sensing cardiac signals connected from said pulse generator to deliver pacing pluses at said sensor rate, said sensor means comprising:
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algorithm means for calculating a measure of the T wave portion of a received intrinsic cardiac signal;
comparing means for comparing said measure with a predetermined criterion to detect the occurrence of the T wave portion of said signal;
data means for determining and storing intrinsic QT interval data and heart rate data for each received intrinsic signal for which a T wave has been detected;
reference means for setting a QT reference curve as a function of said stored intrinsic QT interval and rate data; and
second algorithm means for determining and storing values of evoked QT interval for evoked cardiac signals, and wherein said rate control means comprises calculating means for calculating sensor rate following a ventricular event as a function of said QT reference curve and the evoked QT interval. - View Dependent Claims (6, 7, 8, 9)
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10. A rate responsive pacing system having a pacemaker device and a lead system interconnecting said device and a patient'"'"'s heart, said device having a pulse generator for generating pacing pulses, sensing means for sensing cardiac signals connected from said pulse generator to deliver pacing pulses at said sensor rate, said sensor means comprising:
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algorithm means for calculating a measure of the T wave portion of a received intrinsic cardiac signal;
comparing means for comparing said measure with a predetermined criterion to detect the occurrence of the T wave portion of said signal;
data means for determining and storing intrinsic QT interval data and heart rate data for each received intrinsic signal for which a T wave has been detected;
reference means for setting a QT reference curve as a function of said stored intrinsic QT interval and rate data; and
ectopic means for determining when a sensed cardiac signal represents an ectopic beat, and for setting said sensor rate as unknown for any such ectopic beat. - View Dependent Claims (11)
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12. A rate responsive pacing system having a pacemaker device and a lead system interconnecting said device and a patient'"'"'s heart, said device having a pulse generator for generating pacing pulses, sensing means for sensing cardiac signals connected from said heart by said lead system, sensor means for determining from received cardiac signals a sensor pacing rate, and rate control means for controlling said pulse generator to deliver pulses at said sensor rate, said sensor means comprising:
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rate means for determining values of the patient'"'"'s heart rate each cardiac cycle;
intrinsic means for obtaining QT intervals of intrinsic ventricular signals;
stim means for obtaining evoked QT intervals of stimulated ventricular signals;
compensating means for compensating said evoked QT intervals to obtain compensated QT intervals that correspond to intrinsic QT intervals;
reference means for constructing and storing a QT reference curve from said intrinsic QT intervals and said rate values; and
calculating means for determining said sensor pacing rate from each respective QT and compensated QT interval. - View Dependent Claims (13, 14, 15, 16, 17, 18)
algorithm means for calculating a measure of the T wave portion of a received intrinsic signal; comparing means for comparing said measure with a predetermined criterion to detect the occurrence of an intrinsic T wave; and
timing means for determining the QT time of an intrinsic signal having a detected T wave.
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16. The system as described in claim 15, wherein said algorithm means comprising integrating means for integrating said signal within a predetermined time following the R portion of said signal.
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17. The system as described in claim 16, wherein said comparing means comprises threshold means for comparing said integration with a predetermined threshold value.
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18. The system as described in claim 16, wherein said timing means comprises means for obtaining the slope of said T wave portion and for determining the peak value of said slope.
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19. A method of controlling the pacing rate of a pacing system implanted in a patient, comprising:
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sensing intrinsic patient ventricular signals;
determining from each said sensed signal the time of the R wave and calculating and storing the rate of each last cardiac cycle;
analyzing each said sensed signal within a predetermined time window following the R wave time to determine at least one measure of said signal;
comparing said measure to at least one criterion and detecting the occurrence of a T wave as a function said comparing;
for said detected T wave, determining the time between said R wave and said T wave and storing said time as a value of intrinsic QT;
storing a QT reference curve that provides reference values QT as a function of rate;
comparing each determined value of QT to said reference curve and determining therefrom an indicated pacing rate;
controlling the rate of pacing as a function of said indicated pacing rate;
storing values of intrinsic QT and rate corresponding to each detected T wave, and periodically recalculating said QT reference curve as a function of said stored values; and
determining when a sensed ventricular signal represents an ectopic beat, and inhibiting determination and storing of a QT value for any such ectopic beat. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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26. A method of controlling the pacing rate of a pacing system implanted in a patient, comprising:
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sensing intrinsic patient ventricular signals;
determining from each said sensed signal the time of the R wave and calculating and storing the rate of each last cardiac cycle;
analyzing each said sensed signal within a predetermined time window following the R wave time to determine at least one measure of said signal;
comparing said measure to at least one criterion and detecting the occurrence of a T wave as a function of said comparing;
for a said detected T wave, determining the time between said R wave and said T wave and storing said time as a value of intrinsic QT;
storing a QT reference curve that provides reference values of QT as a function of rate;
comparing each determined value of QT to said reference curve and determining therefrom an indicated pacing rate;
controlling the rate of pacing as a function of said indicated pacing rate; and
determining when there has been a delivered ventricular pace, determining a value of evoked QT for the evoked QRST following a delivered ventricular pace, and compensating said evoked QT to correct for the longer time of an evoked QT compared to an intrinsic QT. - View Dependent Claims (27, 28, 29)
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30. A method of controlling the pacing rate of a pacing system implanted in a patient, comprising:
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sensing intrinsic patient ventricular signals;
determining from each said sensed signal the time of the R wave and calculating and storing the rate of each last cardiac cycle;
analyzing each said sensed signal within a predetermined time window following the R wave time to determine at least one measure of said signal;
comparing said measure to at least one criterion and detecting the occurrence of a T wave as a function of said comparing;
for a said detected T wave, determining the time between said R wave and said T wave and storing said time as a value of intrinsic QT;
storing a QT reference curve that provides reference values of QT as a function of rate;
comparing each determined value of QT to said reference curve and determining therefrom an indicated pacing rate;
controlling the rate of pacing as a function of said indicated pacing rate; and
determining values of evoked QT for evoked ventricular events, compensating said values of evoked QT to substantially equate them to intrinsic values, and determining indicated pacing rate by comparing any determined value of QT to said QT reference curve. - View Dependent Claims (31)
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32. An implantable pacing system for pacing a patient, said system having a pacing generator that generates pacing pulses at a controllable pacing rate and a rate control subsystem for controlling pacing rate, said subsystem comprising:
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signal circuitry for receiving and processing intrinsic patient ventricular signals;
R wave means for detecting the occurrence of an R wave;
T wave means for determining the occurrence of a T wave, said T wave means comprising measure means for obtaining a measure of each said intrinsic signal over a period of time following a detected R wave;
QT means for determining the intrinsic QT interval of an intrinsic signal having a detected R wave and a detected T wave;
rate control mans for controlling pacing rate as a function of determined QT intervals;
DSP circuitry for providing the slope of said intrinsic signal following a detected T wave, and peak means for identifying the maximum value of said slope as the time of a T wave;
storage means for storing values of intrinsic QT and rate for each detected T wave;
reference means for calculating a QT reference curve as a function of said stored values; and
DSP means for determining when a sensed ventricular signal represents an ectopic beat, and inhibiting means for inhibiting determining of a QT value for any such ectopic beat, wherein said T wave means further comprises storage that stores predetermined T wave criteria, and comparing means for comparing said measure with said criteria, and wherein said measure means comprises window means for initiating a window at a predetermined time following a detected R wave, and integrating means for integrating each said received intrinsic signal starting at the initiation of a said window.
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33. An implantable pacing system for pacing a patient, said system having a pacing generator that generates pacing pulses at a controllable pacing rate and a rate control subsystem for controlling pacing rate, said subsystem comprising:
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signal circuitry for receiving and processing intrinsic patient ventricular signals;
R wave means for detecting the occurrence of an R wave;
T wave means for determining the occurrence of a T wave, said T wave means comprising measure means for obtaining a measure of each said intrinsic signal over a period of time following a detected R wave;
QT means for determining the intrinsic QT interval of an intrinsic signal having a detected R wave and a detected T wave;
rate control mans for controlling pacing rate as a function of determined QT intervals;
means for determining the QT interval of evoked ventricular beats and for storing data representative of said evoked QT intervals; and
means for compensating values of QT interval of evoked beats to substantially equate such values with intrinsic values of QT interval. - View Dependent Claims (34)
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Specification