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 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 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.
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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
51 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 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 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. 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 pacing 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 (14, 15, 16, 17, 18, 19)
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20. A method of obtaining intrinsic QT data for a QT sensor used in a cardiac pacing device that is implanted in a patient, comprising:
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receiving patient QRST signals;
determining when an intrinsic R wave has occurred;
initiating a T wave measuring operation after the occurrence of a said R wave;
carrying out said measuring in accordance with a predetermined algorithm and comparing the resultant measure with at least one predetermined criterion to detect the occurrence of a T wave; and
determining the time of a predetermined characteristic of a said received signal that is detected as a T wave, and obtaining a value of QT as the time from said intrinsic R wave to said characteristic time. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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27. 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; and
controlling the rate of pacing as a function of said indicated pacing rate. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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42. 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; and
rate control means for controlling pacing rate as a function of determined QT intervals. - View Dependent Claims (43, 44, 45, 46, 47, 48, 49, 50, 51)
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Specification