Microprocessor controlled rate-responsive pacemaker having automatic rate response threshold adjustment
First Claim
1. A rate-responsive pacemaker comprising:
- pulse generator means for generating pacing pulses at a rate set by a rate control signal;
means for generating a base rate signal;
sensor means for generating a raw sensor signal having a value that varies as a function of a sensed physiological parameter;
processor means for generating a pacing rate signal as a function of said raw sensor signal, wherein said processor means comprises;
preprocessing means for generating one of a plurality of sensor level index signals as a function of the value of said raw sensor signal, said plurality of sensor level index signals including a minimum sensor level index signal corresponding to all values of said raw sensor signal below a first prescribed threshold, and a maximum sensor level index signal corresponding to all values of said raw sensor signal above a second prescribed threshold; and
conversion means for converting said one of a plurality of sensor level index signals to said pacing rate signal;
andselection means for selecting one of said base rate signal or said pacing rate signal as the rate control signal for said pulse generator means, whereby said pulse generator means generates said pacing pulses at a rate determined by the selected one of said base rate signal or said pacing rate signal.
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Abstract
A rate-responsive pacemaker which includes a conventional programmable pulse generator, a physiological sensor, and a processor is disclosed which generates heart stimulation pulses on demand, or as otherwise programmed, as controlled by a rate control signal which is derived from the physiological sensor. The physiological sensor generates a raw signal which varies as a function of some physiological parameter, such as activity level to provide some indication of whether the heart rate should increase or decrease, and hence whether the pacemaker should change the rate at which pacing pulses are provided. The processor converts the raw signal to the sensor-indicated rate signal in accordance with a selectable transfer relationship which defines the sensor-indicated rate signal as a function of a set of discrete sensor level index signals. The sensor-indicated rate signal remains at a minimum value or base rate for all sensor level index signals below a prescribed rate response threshold, with this rate response threshold being set automatically by the processor as a function of a running average of the sensor level index signals monitored over a prescribed time period.
480 Citations
47 Claims
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1. A rate-responsive pacemaker comprising:
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pulse generator means for generating pacing pulses at a rate set by a rate control signal; means for generating a base rate signal; sensor means for generating a raw sensor signal having a value that varies as a function of a sensed physiological parameter; processor means for generating a pacing rate signal as a function of said raw sensor signal, wherein said processor means comprises; preprocessing means for generating one of a plurality of sensor level index signals as a function of the value of said raw sensor signal, said plurality of sensor level index signals including a minimum sensor level index signal corresponding to all values of said raw sensor signal below a first prescribed threshold, and a maximum sensor level index signal corresponding to all values of said raw sensor signal above a second prescribed threshold; and conversion means for converting said one of a plurality of sensor level index signals to said pacing rate signal; and selection means for selecting one of said base rate signal or said pacing rate signal as the rate control signal for said pulse generator means, whereby said pulse generator means generates said pacing pulses at a rate determined by the selected one of said base rate signal or said pacing rate signal. - View Dependent Claims (2, 3, 4, 12, 13, 14)
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5. The rate-responsive pacemaker of claim wherein said conversion means comprises:
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a plurality of transfer functions, each transfer function of said plurality of transfer functions defining a particular relationship between all of said plurality of sensor level index signals and a pacing rate corresponding to each of said sensor level index signals; means for programmably selecting one of said plurality of transfer functions to define the relationship between said sensor level index signals and the pacing rate signal. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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15. In a pacemaker comprising an implantable housing;
- a battery within said housing;
a pacemaker chip within said housing and connected to said battery;
a connector block attached to said housing and said pacemaker chip to which a pacemaker lead may be detachably connected, the improvement comprising;a microprocessor chip within said housing and connected to said pacemaker chip and said battery; memory means coupled to said microprocessor chip for storing program data which controls the operation of said microprocessor chip; sensor means for sensing a physiological parameter and for generating a raw sensor signal as a function thereof; and sensor circuit means for generating one of a plurality of sensor level signals as a function of the energy content of said raw sensor signal, and for presenting said sensor level signal to said microprocessor chip; processing means included in said microprocessor chip, said processing means responsive to the program data stored in said memory means for generating a pacing rate signal which varies in a prescribed manner as a function of the sensor level signal, said pacing rate signal being presented to said pacemaker chip; means, included in said pacemaker chip, for responding to said pacing rate signal in order to alter the rate at which pacing pulses are generated by said pacemaker. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
- a battery within said housing;
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24. A rate-responsive pacemaker comprising:
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a pulse generator having means for generating pulses at a prescribed rate; state logic means for controlling said pulse generator, including whether a pulse is to be generated and, if so, at what rate, said state logic means comprising; state logic registers which, in combination, assume one of a possible plurality of states as a function of signals applied thereto; memory circuitry addressed by said state logic registers, said memory circuitry having prescribed control signals stored therein at each location which is addressable by said state logic; timing circuitry which generates timing signals; sensing circuitry which generates event signals at the occurrence of prescribed events; and logic circuitry responsive to said control signals, timing signals and event signals having output signals which steer said state logic registers as a function of said control, timing and event signals, said state logic registers continuously cycling through various states as a function of the control, timing and event signals applied to said logic circuitry, a pacing cycle comprising a cycle of said state logic from a prescribed reference state, to at least one other state, and back to said reference state; a physiological sensor which generates a raw sensor signal having an energy content that varies as a function of a physiological environment to which said physiological sensor is subjected; a conversion circuit coupled to said sensor, said conversion circuit including means for monitoring the energy content of said raw sensor signal and means for generating a discrete sensor level index signal as a function of said energy content at least once each pacing cycle, said sensor level index signal thereby assuming one of a plurality of possible sensor level signal values once each pacing cycle; processor means coupled to said conversion circuit for defining a sensor indicated rate signal as a function of the sensor level index signal for each pacing cycle; and interface means positioned between said processor means and the memory circuitry of said state logic means for selectively injecting said sensor indicated rate signal into the control signals of said memory circuitry that is presented to said logic circuitry, whereby said sensor indicated rate signal, when so injected, cooperates with the event and timing signals already present to influence the rate at which pulses are generated by said pulse generator. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A rate-responsive pacing system comprising:
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implantable pulse generator means for generating a pacing pulse at a rate set by a rate control signal; means for generating a base rate signal; implantable sensor means for generating a raw sensor signal indicative of a need to change the rate at which said pacing pulses generated by said pulse generator means; implantable processor means coupled to said pulse generator means and said sensor means for generating a sensor indicated rate signal; selection means for programmably selecting one of said base rate signal or said sensor indicated rate signal as the rate control signal controlling said pulse generator means; and automatic reversion means coupled to said selecting means for automatically causing said selection means to select one of said base rate signal or said sensor indicated rate signal as the rate control signal in the event the other of said base rate signal or said sensor indicated rate signal is not generated. - View Dependent Claims (37, 38, 39, 40, 41, 42)
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43. In a rate-responsive pacemaker having means for generating a pacing pulse on demand at a rate determined by a sensor indicated rate signal, said sensor indicated rate signal assuming a value as a function of one of a possible plurality of sensor index signals, said sensor index signals being derived from a sensor adapted to sense a parameter that indicates the rate at which pacing pulses generated by the pacemaker should change, said pacemaker further having histogram memory means for storing said sensor indicated rate signals over time, a method of setting a selectable rate response threshold value for said sensor index signals below which said sensor indicated rate signal remains constant at a minimum sensor indicated rate value and above which said sensor indicated rate signal varies as a function of said sensor index signal, said method comprising the steps of:
- (a) subjecting said pacemaker to a low level of activity;
(b) sampling said sensor indicated rate signal at a prescribed sampling rate during said low level activity period;
(c) sorting and storing each sampled sensor indicated rate signal in said hidtogram memory means as a function of its value;
(d) retrieving and displaying the stored values of said sampled sensor indicated rate signals; and
(e) selecting said rate response threshold value for said sensor index signals to be at least a value which corresponds to the highest sensor indicated rate signal displayed during said low activity period. - View Dependent Claims (44)
- (a) subjecting said pacemaker to a low level of activity;
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45. In a rate-responsive pacemaker having means for generating a pacing pulse on demand at a rate determined by a sensor indicated rate signal, said sensor indicated rate signal assuming a value as a function of one of a possible plurality of sensor index signals, said sensor index signals being derived from a sensor adapted to sense a parameter that indicates the rate at which pacing pulses generated by the pacemaker should change, said pacemaker further having processing means for processing said sensor index signals over time, a method of automatically setting a rate response threshold value for said sensor index signals below which said sensor indicated rate signal remains constant and above which said sensor indicated rate signal varies as a function of said sensor index signal, said method comprising the steps of:
- (a) subjecting said pacemaker to a known level of activity for a prescribed period of time;
(b) processing said sensor index signals to determine a representative sensor index signal over said prescribed period of time;
(c) adding a selectable offset value to the representative sensor index signal determined in step (b), and (d) using the value computed in step (c) as said rate response threshold value. - View Dependent Claims (46, 47)
- (a) subjecting said pacemaker to a known level of activity for a prescribed period of time;
Specification