System and method for automatically determining the slope of a transfer function for a rate-responsive cardiac pacemaker
First Claim
1. A rate-responsive pacemaker for administering pacing pulses to a patient'"'"'s heart in accordance with a predetermined transfer function that correlates sensor measurements representative of the patient'"'"'s level of metabolic need to heart rate, the transfer function being having a base pacing rate, a maximum pacing rate, and a slope defining pacing rates between the base pacing rate and the maximum pacing rate, the rate-responsive pacemaker comprising:
- a pulse generator for generating pacing pulses at a selectable rate between the base pacing rate and the maximum pacing rate in accordance with the predetermined transfer function;
a physiological sensor for generating raw sensor signals indicative of a patient'"'"'s level of metabolic need;
a memory for storing the predetermined transfer function, and for storing selected sensor measurements as a first histogram, the first histogram representing a profile of the patient'"'"'s level of metabolic need over a predetermined period of time, the first histogram defining a frequency distribution of sensor measurements for a plurality of amplitudes; and
a processor, coupled to the pulse generator, the physiological, and the memory, for controlling the rate of pacing pulses, the processor including;
(a) means for processing the raw sensor signals to derive the sensor measurements;
(b) means for determining an appropriate heart rate for the patient'"'"'s level of metabolic need based on the sensor measurements and the corresponding heart rate defined by the transfer function;
(c) means for causing the pulse generator to generate pacing pulses at the appropriate heart rate;
(d) means for selecting sensor measurements for storage in the first histogram; and
(e) means for deriving the slope of the transfer function as a function of the patient'"'"'s profile of metabolic need as represented by the first histogram containing the selected sensor measurements stored over the predetermined period of time.
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Accused Products
Abstract
A rate-responsive pacemaker measures a patient'"'"'s level of activity and stores the results in an activity level histogram. The patient'"'"'s average level of activity is maintained as a running average. Based on a prescribed base pacing rate, a prescribed maximum pacing rate, the average level of activity, and the measured levels of activity stored in the activity level histogram, the rate-responsive pacemaker automatically calculates the slope of the pacemaker transfer function. An activity deviation histogram is also maintained. Analysis of the activity deviation histogram allows the pacemaker to determine if the patient was usually inactive for an extended period of time, and to inhibit an automatic slope calculation under such conditions. If a patient desires to reach a prescribed target heart rate during exercise, the slope may be calculated using the target heart rate and a prescribed fraction of time each week that the patient devotes to exercise.
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Citations
52 Claims
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1. A rate-responsive pacemaker for administering pacing pulses to a patient'"'"'s heart in accordance with a predetermined transfer function that correlates sensor measurements representative of the patient'"'"'s level of metabolic need to heart rate, the transfer function being having a base pacing rate, a maximum pacing rate, and a slope defining pacing rates between the base pacing rate and the maximum pacing rate, the rate-responsive pacemaker comprising:
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a pulse generator for generating pacing pulses at a selectable rate between the base pacing rate and the maximum pacing rate in accordance with the predetermined transfer function; a physiological sensor for generating raw sensor signals indicative of a patient'"'"'s level of metabolic need; a memory for storing the predetermined transfer function, and for storing selected sensor measurements as a first histogram, the first histogram representing a profile of the patient'"'"'s level of metabolic need over a predetermined period of time, the first histogram defining a frequency distribution of sensor measurements for a plurality of amplitudes; and a processor, coupled to the pulse generator, the physiological, and the memory, for controlling the rate of pacing pulses, the processor including; (a) means for processing the raw sensor signals to derive the sensor measurements; (b) means for determining an appropriate heart rate for the patient'"'"'s level of metabolic need based on the sensor measurements and the corresponding heart rate defined by the transfer function; (c) means for causing the pulse generator to generate pacing pulses at the appropriate heart rate; (d) means for selecting sensor measurements for storage in the first histogram; and (e) means for deriving the slope of the transfer function as a function of the patient'"'"'s profile of metabolic need as represented by the first histogram containing the selected sensor measurements stored over the predetermined period of time. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A rate-responsive pacemaker comprising:
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pulse generating means for generating pacing pulses at a selectable rate; physiological sensing means for sensing a patient'"'"'s level of metabolic need; rate selecting means for selecting the rate at which the pulse generating means generates pacing pulses based on the sensed level of metabolic need and the corresponding heart rate defined by a transfer function that correlates metabolic need to heart rate, the transfer function comprising a slope that defines pacing rates between a minimum pacing rate and a maximum pacing rate; slope adjusting means for automatically adjusting the slope of the transfer function in accordance with the level of metabolic need sensed over a predetermined period of time; and inhibiting means for inhibiting the slope adjusting means from automatically adjusting the slope of the transfer function when the patient'"'"'s level of metabolic need over the predetermined period of time is below a threshold level. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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28. A method of providing rate-responsive pacing therapy to a patient'"'"'s heart in accordance with a transfer function that correlates sensor measurements representative of the patient'"'"'s metabolic need to heart rate, the transfer function being having a base pacing rate, a maximum pacing rate, and a slope defining pacing rates between the base pacing rate and the maximum pacing rate, the method comprising the steps of:
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generating pacing pulses at a selectable rate; sensing a patient'"'"'s level of metabolic need and generating raw sensor signals representative thereof; processing the raw sensor signals to derive sensor measurements; determining an appropriate heart rate for the patient'"'"'s level of metabolic need based on the sensor measurements and the corresponding heart rate defined by the transfer function; selecting sensor measurements for storage in the first histogram; storing the selected sensor measurements as a first histogram, the first histogram representing a profile of the patient'"'"'s metabolic need over a predetermined period of time, the first histogram defining a frequency distribution of sensor measurements for a plurality of amplitudes; and deriving the slope of the transfer function as a function of the patient'"'"'s profile of metabolic need as represented by the first histogram containing the selected sensor measurements stored over the predetermined period of time. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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46. A method of providing rate-responsive pacing therapy, comprising the steps of:
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generating pacing pulses at a selectable rate; sensing a patient'"'"'s level of metabolic need; selecting the rate at which pacing pulses are generated based on the sensed level of metabolic need and the corresponding heart rate defined by a transfer function that correlates metabolic need to heart rate, the transfer function comprising a slope that defines pacing rates between a minimum pacing rate and a maximum pacing rate; automatically adjusting the slope of the transfer function in accordance with the level of metabolic need sensed over a predetermined period of time; and inhibiting automatic slope adjustment when the patient'"'"'s level of metabolic need over the predetermined period of time is below a threshold level. - View Dependent Claims (47, 48, 49, 50, 51)
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52. A rate-responsive pacemaker comprising:
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pulse generating means for generating pacing pulses at a selectable rate; physiological sensing means for sensing a patient'"'"'s level of metabolic need; rate selecting means for selecting the rate at which the pulse generating means generates pacing pulses by applying the sensed level of metabolic need to a transfer function that correlates metabolic need to heart rate, the transfer function comprising a slope that defines pacing rates between a minimum pacing rate and a maximum pacing rate, the minimum pacing rate and the maximum pacing rate have a minimum sensor threshold and a maximum sensor threshold associated therewith, respectively; a memory for storing sensor measurements as a first histogram, the first histogram defining a frequency distribution of sensor measurements for a plurality of amplitudes, the first histogram further having a mode with a first amplitude value associated therewith corresponding to the patient'"'"'s average metabolic need, and a second amplitude value at an upper end of the first histogram corresponding to an upper value for the patient'"'"'s metabolic need; means for adjusting the minimum sensor threshold to the first amplitude value; and means for adjusting the maximum sensor threshold to the second amplitude value.
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Specification