Digital cardiac pacemaker with rate limit means

• US 4,515,159 A
• Filed: 03/15/1982
• Issued: 05/07/1985
• Est. Priority Date: 11/06/1978
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Thompson, David L., Hartlaub, Jerome T., McDonald, Ray S., Rossing, Martin A.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US06/358,172
• Time in Patent Office: 1,149 Days
• Field of Search: 128/419 PG, 128/421, 128/422
• US Class Current: 607/9
• CPC Class Codes: A61N 1/37252 Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data

Abstract

A programmable cardiac pacemaker pulse generator utilizing digital circuitry for controlling the provision of cardiac stimulating pulses. The pulse generator is capable of having the rate, the pulse width, the pulse amplitude, the refractory period, the sensitivity and the mode of operation programmed. In addition, the pulse generator can have the output inhibited and can respond to programming signals causing a threshold margin test to be performed, effects of closure of the reed switch overridden, a hysteresis function added and a high rate exceeding the normal upper rate limit programmed. Many of the programmable functions of the pulse generator can either be programmed on a permanent or a temporary basis. The pulse generator further includes means for signaling the acceptance of a programming signal, and means to reset the program acceptance circuit if extraneous signals are detected as programming signals. The program signal acceptance circuit performs several different checks on the detected programming signal including a parity check, an access code check and determining if the proper number of signals were transmitted within a given time. The timing circuit of the pulse generator includes a crystal clock oscillator and counter means for counting the clock pulses therefrom to determine the rate of the pacemaker. The pulse width of each pacemaker pulse is determined by using a voltage controlled oscillator in place of the crystal oscillator to obtain energy compensation due to the battery voltage decreasing with time.

Claims

1. A medical device pulse generator for providing stimulating pulses to output terminals adapted to being electrically coupled to body tissue, said pulse generator comprising:

clock means for providing a series of clock pulses;

counter means for counting said clock pulses;

first decoding means responsive to said counter means for providing a signal whenever said counter means reaches a first certain count, said first count relating to the time between stimulating pulses;

first bistable means for being set in response to said first decoding means signal;

second decoding means responsive to said counter means for providing a signal whenever said counter means reaches a second certain count, said second certain count relating to the minimum acceptable time between stimulating pulses;

second bistable means for being set in response to said second decoding means signal;

gate means responsive to said first and second bistable means for providing a signal when both said first and second bistable means are set;

output means for providing said stimulating pulses in response to said gate means signal;

reset means for resetting said counter means, said first bistable means and said second bistable means in response to the provision of said stimulating pulse; and

override means for providing a signal to enable said gate means to provide a signal whenever said first bistable means is set regardless of the state of said second bistable means, said override means signal only being provided when it is desired to provide stimulating pulses separated by a time period less than the time for said counter means to reach said second count.

2. The invention according to claim 1 wherein said pulse generator further includes override means for providing a signal to enable said gate means to provide a signal whenever said first bistable means is set ragardless of the state of said second bistable means, said override means signal only being provided when it is desired to provide stimulating pulses separated by a time period less than the time for said counter means to reach said second count.

3. The invention according to claim 1 wherein said gate means includes first and second gates, said first gate being responsive to said override means signal and said second bistable means for providing a signal whenever either said override signal is applied thereto or said second bistable means is set, and said second gate being responsive to said first bistable means being set and the signal from said first gate means for providing said gate means signal.

4. The invention according to claim 1,

wherein said output means includes rate limit means for providing said stimulating pulse at a rate not exceeding an upper rate, said rate limit means providing a signal after a certain time related to the time period of stimulating pulses provided at said upper rate;

and

wherein said rate limit means signal is applied to said gate means and said gate means provides said signal only after said rate limit means signal is applied thereto.

5. The invention according to claim 4 wherein said pulse generator further includes override means for providing a signal to enable said gate means to provide a signal regardless of the state of said second bistable means or the provision of said rate limit means signal, said override means signal only being provided when it is desired to provide stimulating pulses separated by a time period less than both said time for said counter means to reach said second count and said certain time.

6. The invention according to claim 5 wherein said gate means includes first, second and third gates, said first gate being responsive to said rate limit signal and said second bistable means being set for providing a signal when both said second bistable means is set and said rate limit signal is provided, said second gate being responsive to said first gate signal and said override means signal for providing a signal whenever either of the signals applied thereto are provided and said third gate being responsive to said first bistable means being set and to the second gate signal for providing said gate means signal.

7. The invention according to claim 6 wherein said override means includes switch means for closing a short circuit path from the output of said rate limit circuit to a predetermined voltage level to override said rate limit circuit.

8. The invention according to claim 5 wherein said override means includes switch means for closing a short circuit path from the output of said rate limit circuit to a predetermined voltage level to override said rate limit circuit.

9. A rate programmable medical device for providing stimulating pulses at a programmed rate defined by a programming signal applied thereto, said medical device comprising:

detector means responsive to said programming signal for providing rate control signals manifesting the programmed rate and for further providing an override signal manifesting that said programmed rate exceeds a certain upper rate whenever said programmed rate exceeds said certain upper rate;

pulse generator means responsive to said rate control signals for providing said stimulating pulses at said programmed rate, said pulse generator means including rate limit means responsive to said override signal for limiting the rate at which said pulse generator means provides said stimulating pulses unless said override signal is applied thereto.

10. The invention according to claim 9 wherein said pulse generator means includes:

oscillator means responsive to said rate control signals for providing control signals at said programmed rate, said oscillator means including rate limit means which, unless disabled, limits the rate at which said oscillator means provides said control signals;

output means responsive to said control signals for providing said stimulating signals; and

rate limit override means responsive to said override signal for disabling said rate limit means.

11. The invention according to claim 10 wherein said oscillator means includes:

clock means for providing a series of clock pulses;

counter means for counting said clock pulses;

first decoding means responsive to said counter means for providing a signal whenever said counter means reaches a first count relating to the time period between stimulating pulses provided at said programmed rate;

first bistable means for being set in response to said first decoding means signal;

second decoding means responsive to said counter means for providing a signal whenever said counter means reaches a second count, said second count being related to a time no longer than the time period between stimulating pulses provided at said limited rate;

second bistable means for being set in response to said second decoding means signal; and

logic means responsive to said first and second bistable means being set for providing said control signals and for resetting said first and second bistable means.

12. The invention according to claim 11 wherein said logic means includes gate means enabled by either said second bistable means being set or the provision of said override signal, said enable gate means providing a signal whenever said first bistable means is set to initiate the provision of said control signal.

13. The invention according to claim 12 wherein said override means provides a signal to enable said gate means to provide a signal whenever said first bistable means becomes set, regardless of whether said rate limit signal is provided or said second bistable means is set.

14. The invention according to claim 9 wherein said override means provides a signal to enable said gate means to provide a signal whenever said first bistable means becomes set, regardless of whether said second bistable means is set.

15. The invention according to claim 11 wherein said output means includes second rate limit means for providing a rate limit signal until a certain time after each stimulating pulse, said certain time being no greater than the time at which said stimulating pulses are provided at said limited rate, said output means further including means disabled by the provision of said rate limit signal for providing said stimulating pulses in response to said control signals.

16. The invention according to claim 15 wherein said logic means includes gate means enabled by either said second bistable means being set or the provision of said override signal, said enable gate means providing a signal whenever said first bistable means is set to initiate the provision of said control signal.

17. The invention according to claim 16 wherein said gate means is disabled by the provision of said rate limit signal.

18. The invention according to claim 17 wherein said override means includes means coupled to the output of said second rate limit means for preventing the provision of said rate limit signal.

19. The invention according to claim 18 wherein said override means provides a signal to enable said gate means to provide a signal whenever said first bistable means becomes set, regardless of whether said rate limit signal is provided or said second bistable means is set.

20. The invention according to claim 17 wherein said override means provides a signal to enable said gate means to provide a signal whenever said first bistable means becomes set, regardless of whether said rate limit signal is provided or said second bistable means is set.

21. The invention according to claim 11 wherein said override means includes means coupled to the output of said second rate limit means for preventing the provision of said rate limit signal.

22. The invention according to claim 9 wherein said pulse generator means includes:

oscillator means responsive to said rate control signals for providing control signal at said programmed rate;

output means responsive to said control signals for providing said stimulating pulses, said output means including second rate limit means which, unless disabled, limits the rate at which said output means provides said stimulating pulses; and

rate limit override means responsive to said override signal for disabling said first and second rate limit means.

23. The invention according to claim 22:

wherein said oscillator includes rate limit means which, unless disabled, limits the rate at which said oscillator provides said control pulses; and

wherein said rate limit override means signal disables said oscillator rate limit means.

24. A medical device pulse generator for providing stimulating pulses to output terminals adapted to being electrically coupled to body tissue, said pulse generator comprising:

clock means for providing a series of clock pulses;

counter means for counting said clock pulses;

first decoding means responsive to said counter means for providing an enabling signal whenever said counter means reaches a certain count relating to the minimum acceptable time and maximum rate of stimulating pulses;

second decoding means for providing a stimulating rate control signal whenever said counter means reaches a further count relating to the time between stimulating pulses;

output means for providing stimulating pulses in response to a stimulating rate signal;

rate limit means for preventing said output means from providing said stimulating pulses at a rate exceeding a further maximum rate corresponding to a further minimum acceptable time between successive stimulating pulses;

means responsive to said rate limit means and said enabling signal for enabling the provision of said stimulating rate control signal to said output means only after the expiration of said minimum acceptable times between stimulating pulses; and

reset means for resetting said counter means to a predetermined initial count in response to the provision of said stimulating pulse.

25. The pulse generator of claim 24 wherein said predetermined initial count is an initial count number other than zero and said reset means resets said counter means to said initial count number;

said certain count is the number zero and said enable means provides said enabling signal whenever said counter means reaches the count zero; and

said further count is a further count number other than zero.

26. The pulse generator of claim 24 further comprising override means for enabling said output means to respond to said stimulating rate control signal in the absence of said enabling signal when it is desired to provide stimulating pulses at a rate exceeding the maximum rate.

27. A medical device pulse generator for providing stimulating pulses separated by a predetermined time interval to terminal means adapted to being coupled to bodily tissue at a defined rate, said pulse generator being susceptible of suffering malfunction such that said rate can exceed said defined rate, said pulse generator comprising:

clock means for providing a series of clock pulses;

digital timing means responsive to said clock signals for establishing said predetermined time interval as a function of the count of a first predetermined number of said clock pulses and for providing an output trigger signal upon expiration of said first predetermined time interval;

digital rate limit means responsive to said clock pulses for establishing a first minimum time interval between output trigger signals as a function of a second predetermined number of clock pulses;

output means responsive to said output trigger signal for providing said stimulating signal, said output means further comprising further rate limit means for establishing a second minimum time interval between stimulating signals; and

logic means for preventing said output means from responding to said output trigger signal until expiration of both said first and second minimum time intervals.

28. The medical device of claim 27 wherein said logic means further comprises means for preventing said output means from receiving an output trigger signal until expiration of said second minimum time interval.

29. The medical device of either claim 27 or claim 28 wherein said digital rate limit means is coupled to said digital timing means and is operative to prevent said digital timing means from providing an output trigger signal until after the first minimum time interval elapses.

30. A body stimulator pulse generator for providing stimulating pulses at a programmed rate defined by an external programming signal applied thereto to terminal means adapted to being coupled to body tissue, comprising digital oscillator means for providing signals at said defined rate, said digital oscillator means including first rate limit means to prevent said oscillator signals from exceeding a first upper rate;

output means responsive to said oscillator signals, for providing said stimulating pulses, said output means including second rate limit means to prevent said stimulating pulses from exceeding a second upper rate, detector means responsive to said programming signal for providing rate control signals manifesting the programmed rate and for further providing a high rate signal whenever said programmed rate exceeds said first or second upper rate, and further means responsive to said high rate signal for overriding said first and second rate limit means.

31. A stimulator pulse generator as claimed in claim 30 wherein said second rate limit means provides a signal to said first rate limit means;

and wherein said first rate limit means responds to said second rate limit means signal by preventing oscillator pulses from being provided at a rate exceeding the lower of said first and second upper rates.

32. A stimulator pulse generator as claimed in claim 30 or 31, further comprising temporary memory means for receiving and storing said high rate control signal;

and means for terminating said high rate programming signal and resetting said further means.

33. A stimulator pulse generator as claimed in claim 32 wherein said output means includes second rate limit means and is arranged to provide said stimulating pulse at a rate not exceeding an upper rate, said second rate limit means providing a signal after a certain time related to the time period of stimulating pulses provided at said upper rate;

and wherein said second rate limit means signal is applied to said gate means and said gate means provides said signal only after said second rate limit means signal is applied thereto.

34. A stimulator pulse generator as claimed in claim 33 wherein said override means is arranged to provide a signal only when it is desired to provide stimulating pulses separated by a time period less than both said time for said counter means to reach said second count and said certain time.

35. A stimulator pulse generator as claimed in claim 34 wherein said gate means includes first, second and third gates, said first gate being responsive to said second rate limit signal and said second bistable means being set for providing a signal when both said second bistable means is set and said rate limit signal is provided, said second gate being responsive to said first gate signal and said override means signal for providing a signal whenever either of the signals applied thereto are provided and said third gate being responsive to said first bistable means being set and to the second gate signal for providing said gate means signal.

36. A body stimulator pulse generator for providing stimulating pulses to output terminals adapted to being electrically coupled to body tissue, said pulse generator comprising:

clock means for providing a series of clock pulses;

counter means for counting said clock pulses;

first decoding means responsive to said counter means for providing a signal whenever said counter means reaches a first certain count, said first count relating to the time between stimulating pulses;

first bistable means for being set in response to said first decoding means signal;

second decoding means responsive to said counter means for providing a signal whenever said counter means reaches a second certain count, said second certain count relating to the minimum acceptable time between stimulating pulses and establishing a first rate limit;

second bistable means for being set in response to said second decoding means signal;

gate means responsive to said first and second bistable means for providing a signal when both said first and second bistable means are set;

output means for providing said stimulating pulses in response to said gate means signal; and

reset means for resetting said counter means, said first bistable means and said second bistable means in response to the provision of said stimulation pulse, said pulse generator further including override means for providing a signal to enable said gate means to provide a signal whenever said first bistable means is set regardless of the state of said second bistable means, said override means signal only being provided when it is desired to provide stimulating pulses separated by a time period less than the time for said counter means to reach said second count.

37. A stimulator pulse generator as claimed in claim 36 wherein said gate means includes first and second gates, said first gate being responsive to said override means signal and said second bistable means for providing a signal whenever either said override signal is applied thereto or said second bistable means is set, and said second gate being responsive to said first bistable means being set and the signal from said first gate means for providing said gate means signal.

38. A stimulator pulse generator as claimed in claim 36 or 37 wherein said override means includes switch means for closing a short circuit path from the output of said second rate limit circuit to a predetermined voltage level to override said rate limit circuit.