Rate responsive cardiac pacemaker

Claim 2

A rate responsive cardiac pacemaker for implantation in a patient, comprising an activity sensor means having a response characteristic limited to the frequency range below 4 Hz for detecting movement of the patient arising from physical exercise and generating an electrical signal representative thereof while discriminating against movement arising from ran­dom influences, means for generating pulses at a controllably variable rate to stimulate the patient's heart at any of a plurality of selectable rates, and means responsive to said signal for adjusting the rate of the pulse generating means relative to a base rate according to whether the patient is undergoing exercise or is at rest.

Claim 3

The rate responsive cardiac pacemaker according to Claim 1, wherein said activity sensor means includes means for selectively establishing at least one activity threshold value indicative of exercise, and wherein said rate adjusting means includes means for setting the rate of said pulse generating means based upon the amplitude of selected portions of said signal relative to said at least one activity threshold value.

Claim 4

The rate responsive cardiac pacemaker according to Claim 2, wherein said rate setting means increases the rate by a predetermined amount when said at least one activity threshold values is exceeded.

Claim 5

The rate responsive cardiac pacemaker according to Claim 3, wherein said threshold establishing means establishes a new higher threshold each time the previous threshold is exceeded, to avoid further rate increases from false trigger­ings attributable to detected movement which is unrelated to exercise.

Claim 6

The rate responsive cardiac pacemaker according to Claim 4, wherein said rate setting means gradually reduces the rate toward said base rate when said signal amplitudes fall to a predetermined percentage of the threshold value which had been exceeded to produce the immediately preceding rate increase.

Claim 7

The rate responsive cardiac pacemaker according to Claim 5, wherein said rate setting means decreases said predetermined amount of the rate increase as each new higher threshold value is successively exceeded.

Claim 8

The rate responsive cardiac pacemaker according to Claim 6, wherein said rate setting means imposes a selectable upper rate limit, beyond which no further increase in rate is permitted.

Claim 9

The rate responsive cardiac pacemaker according to Claim 1, wherein said activity sensor means includes a mechano­electrical transducer responsive to mechanical forces.

Claim 10

The rate responsive cardiac pacemaker according to Claim 8, wherein said mechano-electrical transducer has a geometrical configuration which limits said response charac­teristic to the frequency range below 4 Hz.

Claim 11

The rate responsive cardiac pacemaker according to Claim 1, wherein said activity sensor means differentiates between the rhythmical movement characteristic of physical exercise and the random spasmodic movement characteristic of forces acting upon the sensor means which are unrelated to exercise.

Claim 12

A rate responsive cardiac pacemaker for implantation in a patient, comprising activity sensor means for detecting movement of the patient arising from exercise to generate a signal level representative thereof while discriminating against movement arising from random influences, further sensor means for detecting the value of a physiological parameter com­plementary to movement and indicative of the overall metabolic state of the patient to generate a signal level representative thereof, and means responsive to both sensor means for generat­ing pulses to stimulate the patient's heart at a physiologi­cally appropriate rate determined from the respective signal levels generated by each of said sensor means.

Claim 13

A rate responsive cardiac pacemaker for implantation in a patient, comprising activity sensor means for detecting movement of the patient arising from exercise to generate a signal level representative thereof while discriminating against movement arising from random influences, further sensor means for detecting the value of a physiological parameter com­plementary to movement and indicative of the overall metabolic state of the patient to generate a signal level representative thereof, and means responsive to both sensor means for generat­ing pulses to stimulate the patient's heart at a physiologi­cally appropriate rate determined from the respective signal levels generated by each of said sensor means.

Claim 14

The rate responsive cardiac pacemaker according to Claim 11, wherein said pulse generating means includes means for establishing a predetermined period of time, first means for controlling the rate of said pulse generating means in response to relative changes of the signal level of said activity sensor means during said predetermined period of time, and second means for controlling the rate of said pulse generating means in response to the signal level generated by said further complementary parameter sensor means depending on the rate determined thereby compared to the rate determined by said activity sensor means during said time period.

Claim 15

The rate responsive cardiac pacemaker according to Claim 12, wherein said first controlling means retains control of the rate of said pulse generating means if the rate deter­mined by said activity sensor means exceeds the rate determined by said further complementary parameter sensor means throughout said time period, and said second controlling means assumes control of the rate of said pulse generating means if the rate determined by said further complementary parameter sensor means exceeds the rate determined by said activity sensor means at any point during said time period.

Claim 16

The rate responsive cardiac pacemaker according to Claim 13, wherein said first controlling means includes means for selectively establishing an activity threshold value for detection of exercise, means for comparing a selected portion of the signal level generated by said activity sensor means to said threshold value, and means for increasing the rate of said pulse generating means when said selected portion of the activity sensor means signal level exceeds said threshold value.

Claim 17

The rate responsive cardiac pacemaker according to Claim 14, wherein said first controlling means further includes means for gradually reducing the rate of said pulse generating means when said activity sensor means signal level falls to a predetermined level below said threshold value.

Claim 18

The rate responsive cardiac pacemaker according to Claim 14, wherein said threshold establishing means establishes the exceeded threshold value as a new baseline value for activity detection.

Claim 19

The rate responsive cardiac pacemaker according to Claim 14, wherein said threshold establishing means is responsive to the threshold value having been exceeded, for establishing a new higher threshold value indicative, when exceeded, of additional exercise.

Claim 20

The rate responsive cardiac pacemaker according to Claim 17, wherein said first controlling means further includes means responsive to the establishment of a new higher threshold value for constituting the exceeded threshold value as a new baseline value linking a predetermined base rate and the higher threshold value.

Claim 21

The rate responsive cardiac pacemaker according to Claim 11, wherein said activity sensor means has a frequency response characteristic limited to the range between about 0.3 Hz and about 4 Hz.

Claim 22

A rate responsive cardiac pacemaker for implantation in a patient, comprising first sensor means for detecting rhythmic physical exercise by the patient and generating an electrical signal representative thereof while discriminating against random disturbances, second sensor means for detecting the value of a physiological parameter of the body further indicative of exercise, means for generating pulses at a controllably variable rate to stimulate the patient's heart at any of a plurality of selectable rates at which the pulses are applied to the heart, and means responsive to both said signal and the detected value of said physiological parameter for adjusting the rate of the pulse generating means according to one or the other of them at any given point in time based on the relative values of the separate rates dictated by each within a predetermined period of time and further based on the amplitude of said signal relative to a selectable threshold value indicative of exercise.

Claim 23

A rate responsive cardiac pacemaker for implantation in a patient, comprising first sensor means for detecting rhythmic physical exercise by the patient and generating an electrical signal representative thereof while discriminating against random disturbances, second sensor means for detecting the value of a physiological parameter of the body further indicative of exercise, means for generating pulses at a controllably variable rate to stimulate the patient's heart at any of a plurality of selectable rates at which the pulses are applied to the heart, and means responsive to both said signal and the detected value of said physiological parameter for adjusting the rate of the pulse generating means according to one or the other of them at any given point in time based on the relative values of the separate rates dictated by each within a predetermined period of time and further based on the amplitude of said signal relative to a selectable threshold value indicative of exercise.