System and method for adjusting sensor threshold in a rate responsive pacemaker
First Claim
1. A rate responsive cardiac pacemaker, comprising:
- a pace pulse generator for generating cardiac pace pulses, and rate control means for controlling the rate of generation of said pace pulses, said rate control means havinga sensor responsive to a predetermined patient parameter for continuously providing a sensor output signal having a varying signal level,processing means for processing said sensor output signal to provide a count signal for use in controlling said rate whenever said sensor output signal meets predetermined sensor output signal level criteria,accumulating means for accumulating data representative of said count signals over respective predetermined periods of time, and adjusting means for adjusting said criteria as a function of said data.
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Abstract
There is provided a rate responsive pacemaker system and method employing an activity-type sensor for deriving signals for determining pacing rate, wherein the activity sensor threshold is automatically adjusted as a function of monitored sensor output. In a preferred embodiment, activity counts are categorized on a histogram basis, and the histogram data is stored over a selected period of time. The activity data in histogram form is then analyzed and compared to predetermined criteria to determine whether threshold seems to be proper, or whether threshold adjustment is indicated. The adjustment algorithm provides different degrees of adjustment depending upon the circumstances. Specifically, where the data suggests too many or too few counts within an expected range, the threshold is adjusted as a function of whether the analyzed outputs are only a little bit out of the expected range or quite a bit out of the expected range. The algorithm also determines whether the sensor response accurately reflects patient rest. Another specific feature of the invention is determination of when the sensor is picking up false positives and thus improperly responding to extraneous signals such as patient'"'"'s cardiac contractions.
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Citations
14 Claims
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1. A rate responsive cardiac pacemaker, comprising:
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a pace pulse generator for generating cardiac pace pulses, and rate control means for controlling the rate of generation of said pace pulses, said rate control means having a sensor responsive to a predetermined patient parameter for continuously providing a sensor output signal having a varying signal level, processing means for processing said sensor output signal to provide a count signal for use in controlling said rate whenever said sensor output signal meets predetermined sensor output signal level criteria, accumulating means for accumulating data representative of said count signals over respective predetermined periods of time, and adjusting means for adjusting said criteria as a function of said data. - View Dependent Claims (2, 3, 4)
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5. A rate responsive cardiac pacemaker having a controllable pulse generator for generating pacing pulses at a controllable rate, and rate control means responsive to patient activity for controlling said rate, said rate control means comprising
activity sensor means for continuously providing an activity signal representative of patient activity and having a varying amplitude, and for producing an output count signal whenever said activity signal exceeds a predetermined amplitude threshold, rate means for generating a rate control signal as a function of produced count signals, data means for accumulating data reflective of the history of said output count signals, and adjusting means for adjusting said amplitude threshold as a function of said accumulated history.
- 10. A rate responsive pacemaker having a pace pulse generator for generating pace pulses, rate responsive means for deriving activity signals representative of patient activity and for developing rate control signals as function of said activity signals, rate means for classifying the rate of said activity signals over each of a plurality of successive time intervals, and means for detecting the occurrence of false positive activity signals as a function of said classifying.
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12. A method for automatically adjusting the threshold of an activity-type sensor circuit in a pacemaker implanted in a patient comprising
detecting outputs from said sensor circuit over a predetermined adjustment time period; -
classifying said outputs with respect to predetermined classification criteria; analyzing said classified outputs with respect to predetermined decision data; and adjusting said threshold as a function of said analyzing. - View Dependent Claims (13, 14)
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Specification