Threshold tracking system and method for stimulating a physiological system

Claim 3

The method as described in claim 1, wherein said second time interval is less than said first time interval.

Claim 4

The method as described in claim 1, wherein said series of backup pulses is generated within the time interval between successive stimulation pulses.

Claim 5

The method as described in claim 3, wherein the first of said series of backup pulses is generated within about 40-50 ms following said each such stimulation pulse, and each succeeding backup pulse is generated and connected to the body organ within about 40-50 ms following the prior backup pulse.

Claim 6

The method as described in claim 1, wherein the first backup pulse has an intensity level greater than the immediately preceding stimulating pulse, and each successive backup pulse has an intensity level greater than the previous backup pulse.

Claim 7

The method as described in claim 5, wherein the energy level of successive backup pulses increases in predetermined increments.

Claim 8

The method as described in claim 5, wherein the pulse width of successive backup pulses is increased relative to respective preceding backup pulses.

Claim 9

The method as described in claim 5, wherein said series comprises three backup pulses.

Claim 10

The method as described in claim 5, further comprising resetting the energy level of the next succeeding stimulation pulse after the step of connecting a backup pulse to said organ.

Claim 11

The method as described in claim 9, comprising determining the stimulus level at which a backup pulse first evokes responsive physiological activity following sensing failure of occurrence of said physiological activity and setting the energy level of the next succeeding stimulation pulse at a predetermined safe energy level above said evoking level.

Claim 12

The method as described in claim 5, wherein the number of said backup pulses connected is limited to a predetermined number.

Claim 13

The method as described in claim 1, comprising changing the energy level of said stimulation pulses in a predetermined way until said failure is sensed.

Claim 14

A demand type pacing system for stimulating cardiac response of a patient, said system having means for delivering signals to and receiving signals from said patient''s heart, comprising: a. means for sensing to determine the occurrence of heartbeats of said patient; b. means for generating periodic stimulation pulses for stimulating heartbeats in said patient; c. first connecting means for connecting one of said stimulation pulses to said heart whenever absence of a heartbeat is sensed for a first predetermined time interval; d. backup means for generating, following each such generated stimulation pulse, a predetermined series of backup pulses, said backup pulses having a predetermined time and energy relationship to the preceding stimulation pulse; e. second connecting means, for connecting the pulses of said series serially to said patient''s heart following the failure of a sensed heartbeat within a second predetermined time interval following connection of one of said stimulation pulses.

Claim 15

A demand type pacing system for stimulating cardiac response of a patient, said system having means for delivering signals to and receiving signals from said patient''s heart, comprising: a. means for sensing to determine the occurrence of heartbeats of said patient; b. means for generating periodic stimulation pulses for stimulating heartbeats in said patient; c. first connecting means for connecting one of said stimulation pulses to said heart whenever absence of a heartbeat is sensed for a first predetermined time interval; d. backup means for generating, following each such generated stimulation pulse, a predetermined series of backup pulses, said backup pulses having a predetermined time and energy relationship to the preceding stimulation pulse; e. second connecting means, for connecting the pulses of said series serially to said patient''s heart following the failure of a sensed heartbeat within a second predetermined time interval following connection of one of said stimulation pulses.

Claim 16

The system as described in claim 13, wherein each successive backup pulse has a greater energy level, and comprising means for readjusting the energy level of fOllowing stimulation pulses as a function of the energy level of the backup pulse which evokes a heartbeat.

Claim 17

The system as described in claim 14, comprising means for changing the energy level of said stimulation pulses in a predetermined way until said failure to sense said heartbeat occurs.

Claim 18

In a system for sensing and stimulating responses in a physiological system of a human patient, apparatus comprising the combination of stimulus generating means for generating periodic stimulus signals and threshold testing means for determining the stimulus threshold for evoking a response with a generated stimulus signal, said threshold testing means comprising a. program means for programming changes in the level of said stimulus signals and for detecting threshold by determining the stimulus level which first fails to evoke a response, b. backup means for generating at least one backup stimulus signal of a level greater than said first level and following such first stimulus within an interval such that no response is missed, c. memory means for remembering the level of the last generated stimulus signal, and d. logic means operating in combination with said memory means to set the next succeeding periodic stimulus signal following threshold detection at a level providing a predetermined safety margin.

Claim 19

In a system for sensing and stimulating responses in a physiological system of a human patient, apparatus comprising the combination of stimulus generating means for generating periodic stimulus signals and threshold testing means for determining the stimulus threshold for evoking a response with a generated stimulus signal, said threshold testing means comprising a. program means for programming changes in the level of said stimulus signals and for detecting threshold by determining the stimulus level which first fails to evoke a response, b. backup means for generating at least one backup stimulus signal of a level greater than said first level and following such first stimulus within an interval such that no response is missed, c. memory means for remembering the level of the last generated stimulus signal, and d. logic means operating in combination with said memory means to set the next succeeding periodic stimulus signal following threshold detection at a level providing a predetermined safety margin.

Claim 20

The system as described in claim 16, comprising logic means for combining said backup means operatively with said program means in a manner such that upon any said failure to evoke a response with a stimulus signal the next succeeding heartbeat normally due in said patient is evoked by a backup stimulus signal, whereby there is no missed heartbeat.

Claim 21

The system as described in claim 16, in combination with sensing means adapted for sensing cardiac responses and stimulus delivery means for delivering said stimulus signals to the heart of a human patient, and wherein said sensing means is adapted to detect the presence or absence of an evoked response to a delivered stimulus signal within a time period of 20-50 ms following the delivery of said stimulus.

Claim 22

The system as described in claim 16, wherein said threshold testing means comprises logic means for carrying out threshold testing in a programmed cycle mode.

Claim 23

The system as described in claim 16, wherein said threshold testing means comprises logic means for carrying out said threshold testing in a continuous mode.

Claim 24

The system as described in claim 16, wherein said memory means comprises an up/down counter.

Claim 25

The system as described in claim 16, comprising manual testing means for testing for threshold.

Claim 26

The system as described in claim 16, comprising means for sensing signal interference and means for inhibiting said programmed changes during said sensed signal interference.

Claim 27

The system as described in claim 23, comprising means for increasing the intensity level of said stimulus signals upon sensing of said signal interference.

Claim 28

Demand pacing apparatus for stimulating cardiac responses in a patient, comprising: a. sensing means for periodically sensing to determine the occurrence of heartbeats; b. generator means for generating pacing signals at a predetermined repetition rate; c. connecting means operatively responsive to said sensing means for connecting said pacing signals to said patient''s heart when the patient''s heartbeat is not sensed for a predetermined interval defined by said repetition rate; d. second generating means for generating a predetermined series of backup pulses following each said generating pacing signal; and e. logic means, operatively responsive to said sensing means, for connecting the pulses of said series of backup pulses serially to the heart when no heartbeat is sensed following a connected pacing signal, until a heartbeat is evoked.

Claim 29

Demand pacing apparatus for stimulating cardiac responses in a patient, comprising: a. sensing means for periodically sensing to determine the occurrence of heartbeats; b. generator means for generating pacing signals at a predetermined repetition rate; c. connecting means operatively responsive to said sensing means for connecting said pacing signals to said patient''s heart when the patient''s heartbeat is not sensed for a predetermined interval defined by said repetition rate; d. second generating means for generating a predetermined series of backup pulses following each said generating pacing signal; and e. logic means, operatively responsive to said sensing means, for connecting the pulses of said series of backup pulses serially to the heart when no heartbeat is sensed following a connected pacing signal, until a heartbeat is evoked.

Claim 30

The apparatus as described in claim 25, wherein said second generating means is further characterized by generating said series of backup pulsEs such that each backup pulse has a predetermined time relation to the prior pacing signal.

Claim 31

The apparatus as described in claim 25, comprising programming means for causing programmed changes in the energy level of said pacing signals, whereby threshold testing is carried out.

Claim 32

In a demand pacing apparatus which generates periodic pacing stimulus signals for cardiac pacing of a patient, which apparatus is adapted to transmit said pacing signals for delivery to the patient''s heart and to receive patient signals representative of cardiac response, a threshold tracking system for determining the patient''s cardiac threshold to said pacing stimulus signals, said threshold tracking system comprising; a. digital increment means for controlling the intensity of said pacing stimulus signals to predetermined incremental levels; b. program means in combination with said digital increment means for setting the intensity of said pacing stimulus signals; c. means for detecting threshold by determining when a stimulus signal of a given level fails to evoke a cardiac response; d. said threshold detecting means including means for generating a series of signals during the time interval between said detected failure and the next periodic pacing signal; and e. logic means for programming said digital increment means in response to detected threshold, whereby said pacing signals are programmed to be of an intensity above said threshold following such failure.

Claim 33

In a demand pacing apparatus which generates periodic pacing stimulus signals for cardiac pacing of a patient, which apparatus is adapted to transmit said pacing signals for delivery to the patient''s heart and to receive patient signals representative of cardiac response, a threshold tracking system for determining the patient''s cardiac threshold to said pacing stimulus signals, said threshold tracking system comprising; a. digital increment means for controlling the intensity of said pacing stimulus signals to predetermined incremental levels; b. program means in combination with said digital increment means for setting the intensity of said pacing stimulus signals; c. means for detecting threshold by determining when a stimulus signal of a given level fails to evoke a cardiac response; d. said threshold detecting means including means for generating a series of signals during the time interval between said detected failure and the next periodic pacing signal; and e. logic means for programming said digital increment means in response to detected threshold, whereby said pacing signals are programmed to be of an intensity above said threshold following such failure.

Claim 34

The system as described in claim 28, wherein said digital imcrement means comprises up/down counter logic circuitry.

Claim 35

The system as described in claim 28, wherein said program means comprises threshold searching means for searching for the patient''s threshold.

Claim 36

The system as described in claim 28, wherein said threshold detecting means comprises prebackup control means to control the operation of said series generating means.

Claim 37

The system as described in claim 28, wherein said logic means controls the intensity of said pacing signals to a level above the detected threshold level which corresponds to a predetermined margin of safety.

Claim 38

A demand pacer for cardiac pacing, adapted to operate with a connecting system for delivering signals to and receiving signals from a patient, comprising: a. stimulating means for generating heart stimulating pulses; b. detecting means for detecting natural heartbeats and inhibiting means for inhibiting said stimulating means on the occurrence of natural heartbeats; c. interference sensing means for sensing interference signals; d. means for testing for the threshold to said heart stimulating pulses of the patient being paced by the pacer; e. means for inhibiting said threshold testing during the presence of said sensed interference signals; and f. means for increasing the intensity of said heart stimulating pulses upon sensing interference signals.

Claim 39

A demand pacer for cardiac pacing, adapted to operate with a connecting system for delivering signals to and receiving signals from a patient, comprising: a. stimulating means for generating heart stimulating pulses; b. detecting means for detecting natural heartbeats and inhibiting means for inhibiting said stimulating means on the occurrence of natural heartbeats; c. interference sensing means for sensing interference signals; d. means for testing for the threshold to said heart stimulating pulses of the patient being paced by the pacer; e. means for inhibiting said threshold testing during the presence of said sensed interference signals; and f. means for increasing the intensity of said heart stimulating pulses upon sensing interference signals.

Claim 40

A demand type pacing system for stimulating cardiac response of a patient, said system having means for delivering signals to and receiving signals from said patient''s heart, comprising: a. means for sensing to determine the occurrence of heartbeats of said patient; b. means for generating periodic stimulation pulses for stimulating heartbeats in said patient; c. first connecting means for connecting one of said stimulation pulses to said heart whenever absence of a heartbeat is sensed for a first predetermined time interval; d. backup means for generating, following each such generated stimulation pulse, a predetermined series of backup pulses; e. second connecting means, for connecting the pulses of said series serially to said patient''s heart following the failure of a sensed heartbeat within a second predetermined time interval following connection of one of said stimulation pulses; f. logic means connected to said backup means for controlling the value of each pulse of said series, and having an input for receiving lOgic signals, said controlling being a function of said received logic signals; and g. failure logic signal means connected to said sensing means for generating a failure logic signal when said failure is sensed, said failure logic signals being connected to said input circuit, whereby said series pulses are logically controlled by said logic means following each said failure.

Claim 41

A demand type pacing system for stimulating cardiac response of a patient, said system having means for delivering signals to and receiving signals from said patient''s heart, comprising: a. means for sensing to determine the occurrence of heartbeats of said patient; b. means for generating periodic stimulation pulses for stimulating heartbeats in said patient; c. first connecting means for connecting one of said stimulation pulses to said heart whenever absence of a heartbeat is sensed for a first predetermined time interval; d. backup means for generating, following each such generated stimulation pulse, a predetermined series of backup pulses; e. second connecting means, for connecting the pulses of said series serially to said patient''s heart following the failure of a sensed heartbeat within a second predetermined time interval following connection of one of said stimulation pulses; f. logic means connected to said backup means for controlling the value of each pulse of said series, and having an input for receiving lOgic signals, said controlling being a function of said received logic signals; and g. failure logic signal means connected to said sensing means for generating a failure logic signal when said failure is sensed, said failure logic signals being connected to said input circuit, whereby said series pulses are logically controlled by said logic means following each said failure.

Claim 42

The system as described in claim 34, wherein said logic means controls said backup pulses such that each successive backup pulse has a greater energy level, and further comprising readjustment means connected to said logic means for readjusting the energy level of the next successive stimulation pulse following failure.