Exercise-responsive rate-adaptive cardiac pacemaker
First Claim
1. A rate-responsive cardiac pacemaker, comprisingmeans for sensing the central venous blood temperature of the patient,means responsive to the sensed blood temperature for detecting the onset of exercise by the patient by recognition of the characteristic drop in blood temperature associated therewith, andadjusting means responsive to detection of the onset of exercise for thereupon stepping up the stimulation rate of the pacemaker.
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Abstract
A temperature driven rate responsive cardiac pacemaker adapted to distinguish between physiologically determined changes of the patient'"'"'s blood temperature under conditions of exercise and non-exercise, and to adaptively vary the rate at which stimuli are generated accordingly, is also capable of recognizing the blood temperature dip which is characteristic of the commencement of exercise. In response to such a temperature dip, the pacemaker initiates a rapid and physiologically beneficial increase in the stimulation rate. To assure the proper selective initiation of a rate increase, the pacemaker discriminates between a blood temperature drop indicative of the onset of exercise and those temperature drops which occur for other reasons, such as upon cessation of exercise or as normal phasic variations, including respiration and circadian fluctuations.
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Citations
18 Claims
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1. A rate-responsive cardiac pacemaker, comprising
means for sensing the central venous blood temperature of the patient, means responsive to the sensed blood temperature for detecting the onset of exercise by the patient by recognition of the characteristic drop in blood temperature associated therewith, and adjusting means responsive to detection of the onset of exercise for thereupon stepping up the stimulation rate of the pacemaker.
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6. A stimulus generator for a temperature driven rate responsive cardiac pacemaker, comprising
means responsive to the temperature of the central venous blood of the patient for detecting the onset of exercise by the patient by recognition of the characteristic drop in blood temperature associated therewith, means responsive to the metabolic state of the patient for distinguishing said characteristic drop in blood temperature from decreases of the blood temperature attributable to other causes, and adjusting means responsive to detection of the onset of exercise for abruptly increasing the stimulation rate of the generator.
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12. In an implantable cardiac pacemaker for adaptively varying the heart rate of a patient based on the level of the patient'"'"'s central venous blood temperature, the improvement comprising
means for detecting a drop of predetermined extent and duration in the blood temperature from a time when the patient is in a resting state, as indicative of the commencement of physical activity by the patient, and means responsive to said detection for rapidly increasing the stimulation rate of the pacemaker in an amount and for a time commensurate with physiological response to the commencement of exercise in a healthy person with a normally functioning heart.
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13. An exercise responsive cardiac pacemaker, comprising
means for controllably varying the stimulation rate of the pacemaker according to whether the patient is at rest or undergoing exercise, based on the instantaneous level of the patient'"'"'s blood temperature, and means responsive to a relatively rapid drop in the patient'"'"'s blood temperature commencing from an apparent state of rest of the patient, as indicating commencement of exercise by the patient, and for thereupon increasing the stimulation rate to a level consistent with exercise.
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14. A cardiac pacemaker including a control means for automatic adaptation of the stimulation rate of the pacemaker to the metabolic state of the patient, said control means comprising
a temperature sensor for detecting the central venous blood temperature of the patient, said sensor disposed for introduction into a preselected chamber of the right side of the patient'"'"'s heart, and circuit means connected to the sensor for controlling said stimulation rate, said circuit means including means responsive to a preselected physiological parameter indicative of metabolic state of the patient for determining therefrom whether the patient is then at rest or undergoing exercise, means executing separate algorithms defining stimulation rate as a function of blood temperature for rest state and exercise state of the patient, respectively, and responsive to said determination and to the detected blood temperature for regulating said stimulation rate according to the respective algorithm representative of the determined state of the patient, and means responsive to the coincidence of (i) said stimulation rate being regulated according to one of said algorithms representative of the rest state of the patient, (ii) the then-current stimulation rate being less than a predetermined value, and (iii) a drop in the detected blood temperature exceeding a predetermined minimum amount within a predetermined time interval, for thereupon increasing the stimulation rate by a preset amount.
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18. A method for adaptively regulating an exercise responsive cardiac pacemaker in which the stimulation rate is based on the central venous blood temperature of the patient according to whether the patient is resting or undergoing exercise, said method comprising
detecting a drop in the blood temperature exceeding a predetermined amount within a predetermined time interval, at a time when the patient is in an apparent state of rest with a heart rate not exceeding a predetermined threshold rate, treating such detected temperature drop as denoting the onset of exercise by the patient, and abruptly increasing the stimulation rate to a rate consistent with that of a healthy person with a normal functioning heart, coincident with such detection.
Specification