A system and method for maintaining stimulation pulse amplitude at battery depletion by self-regulating current drain usage

Claim 2

The system as recited in Claim 1, wherein the signal processor comprises: rate responsive processing means for processing a raw sensor signal indicative of physiological need and producing a sensor-indicated rate signal as an output, the rate responsive processing means being capable of varying the rate of stimulation pulses between a programmable minimum rate and a programmable maximum rate in accordance to the sensor-indicated rate signal, wherein the mode of operation having a higher current drain comprises generating a sensor-indicated rate signal at a high rate and the mode of operation having a lower current drain comprises generating a sensor-indicated rate signal at a progressively lower rate until either the battery voltage rises above the first predetermined voltage or a predetermined rate limit is reached.

Claim 3

The system as recited in Claim 2, wherein the predetermined rate limit is equal to the programmable minimum rate.

Claim 4

The system as recited in Claim 1, further comprising: wherein the signal processor is operable in a waveform analysis mode wherein cardiac signal waveforms are analyzed for anomalities, and wherein the mode of operation having a higher level of current drain comprises operating in the waveform analysis mode at a high sampling rate and the mode of operation having a lower level of current drain comprises operating in the waveform analysis mode at a progressively lower sampling rate until either the battery voltage rises above the first predetermined voltage or the minimum sampling rate is reached.

Claim 5

In an implantable stimulation device, a system for maintaining a constant stimulation pulse amplitude and for preventing rapid battery depletion, the system comprising: a battery having a battery voltage which is dependent on current drain from the battery; a battery voltage threshold detector for monitoring the battery voltage of the battery, the battery voltage threshold detector detecting when the battery voltage drops at least to a first predetermined voltage; a pulse generator for generating stimulation pulses to a patient's heart, the stimulation pulses having a constant amplitude when the battery voltage is above the first predetermined voltage; a signal processor coupled to the battery voltage threshold detector, the signal processor being capable of operating in a mode of operation having at least a first and a second level of current drain, the first level of current drain being higher than the second level of current drain; and means for switching the mode of operation from the first level of current drain to the second level of current drain when the battery voltage threshold detector detects that the battery voltage is below the first predetermined voltage, whereby current drain is reduced and the stimulation pulse amplitude is maintained constant for as long as possible.

Claim 6

The system as recited in Claim 5, wherein the signal processor is capable of operating the mode of operation in a plurality of current drain levels, each current drain level being progressively lower in current drain than the previous level of current drain, wherein the switching means is capable of switching the mode of operation from the second level of current drain to a progressively lower level of current drain each time the battery voltage threshold detector detects that the battery voltage is below the first predetermined voltage until either the battery voltage rises above the first predetermined voltage or a predetermined limit is reached.

Claim 7

The system as recited in Claim 6, wherein the signal processor comprises: rate responsive processing means for processing a signal indicative of physiological need and producing a physiologically-indicated rate signal as an output, the rate responsive processing means being capable of operating in a rate responsive pacing mode wherein the rate of stimulation pulses is varied between a programmable minimum rate and a programmable maximum rate in accordance with the physiologically-indicated rate signal, wherein the mode of operation in a plurality of current drain levels comprises operating in a rate responsive pacing mode at a plurality of stimulation rates, the plurality of stimulation rates being progressively lower in stimulation rate corresponding to progressively lower current drain levels.

Claim 8

The system as recited in Claim 6, wherein the signal processor comprises: means for analyzing cardiac signal waveforms for anomalities thereof, the analyzing means being capable of operating in a waveform analysis mode at a plurality of sampling rates, wherein the mode of operation in a plurality of current drain levels comprises operating in the waveform analysis mode with a progressively lower in sampling rate.

Claim 9

An implantable rate responsive pacemaker, comprising: a battery having a battery voltage which is dependent on current drain from the battery; a battery voltage threshold detector for monitoring the battery voltage of the battery, the battery voltage threshold detector detecting when the battery voltage drops at least to a first predetermined voltage; a sensor for sensing physiological need of a patient and for generating a raw sensor signal in response thereto; processing means for generating a sensor-indicated rate signal based on the raw sensor signal as sensed by the sensor; a pulse generator for generating stimulation pulses according to the sensor-indicated rate signal generated by the processing means; means for decreasing the sensor-indicated rate signal when the battery voltage threshold detector detects that the battery voltage is below the first predetermined voltage.

Claim 10

The implantable rate responsive pacemaker as recited in Claim 9, wherein the decreasing means repeatedly decreases the sensor-indicated rate signal until either the battery voltage rises above the first predetermined voltage or a predetermined rate limit is reached.

Claim 11

The implantable rate responsive pacemaker as recited in Claim 10, wherein the predetermined rate limit is equal to the predetermined minimum rate.

Claim 12

The implantable rate responsive pacemaker as recited in Claim 10, wherein the predetermined rate limit is a rate lower than the predetermined minimum rate.

Claim 13

The implantable rate responsive pacemaker as recited in Claim 10, the pacemaker having a first predetermined time period corresponding to battery end of life and a second predetermined time period preceding the first predetermined time period by at least one month, said second predetermined time period corresponding to battery recommended replacement time, wherein the first predetermined voltage corresponds to the battery voltage at which the battery recommended replacement time occurs.

Claim 14

An implantable rate responsive pacemaker as recited in Claim 9, wherein the processing means comprises: means for generating an allowable maximum sensor rate, the allowable maximum sensor rate having a value between the programmable base rate and the programmable maximum sensor rate; and means for limiting the sensor-indicated rate to the programmable maximum sensor rate prior to detecting the battery voltage below the first predetermined value and for limiting the sensor-indicated rate to the allowable maximum sensor rate after the battery voltage is detected below the first predetermined value.

Claim 15

The implantable rate responsive pacemaker as recited in Claim 14, wherein the means for generating an allowable maximum sensor rate comprises: means for periodically monitoring the battery voltage threshold detector to determine whether the battery voltage has dropped at least to the first predetermined voltage; means for adjusting the allowable maximum sensor rate towards the programmable base rate whenever the monitoring means indicates at least once that the battery voltage threshold detector has detected the battery voltage at or below the first predetermined voltage; and means for adjusting the allowable maximum sensor rate towards the programmable maximum sensor rate whenever the monitoring means indicates at least a prescribed number of consecutive times that the battery threshold detector has detected the battery voltage above the first predetermined voltage.

Claim 16

The implantable rate responsive pacemaker as recited in Claim 15, wherein the prescribed number of consecutive times that the battery threshold detector has detected the battery voltage above the first predetermined voltage is at least two.

Claim 17

The implantable rate responsive pacemaker as recited in Claim 9, wherein the processing means further comprises: means for comparing the sensor-indicated rate signal to the programmable base rate whenever the battery voltage threshold detector indicates that the battery voltage is at or below the first predetermined voltage; means for counting the number of occurrences in which the sensor-indicated rate signal is equal to the programmable base rate; and means for suspending rate responsive processing when the counter means is equal to a predetermined value.

Claim 18

In an implantable stimulation device, a system for maintaining a constant stimulation pulse amplitude and for preventing rapid battery depletion, the system comprising: a battery having a battery voltage which is dependent on current drain from the battery; a battery voltage threshold detector for monitoring the battery voltage of the battery, the battery voltage threshold detector detecting when the battery voltage drops to a selected one of a plurality of voltage thresholds, the plurality of thresholds being selected according to a predetermined priority; a pulse generator for generating stimulation pulses to a patient's heart, the stimulation pulses having a constant amplitude when the battery voltage is above the first predetermined voltage; a processor, coupled to the battery voltage threshold detector, which processor is capable of operating in a plurality of high current drain modes of operation and in at least two progressively lower current drain modes of operation; and means for successively switching from one of the high current drain modes of operation to one of the progressively lower current drain modes of operation whenever the battery threshold detector detects that the battery voltage is below the selected one of the plurality of thresholds.