Implantable digital cardiac pacer having externally selectible operating parameters and "one shot" digital pulse generator for use therein

• US 4,049,004 A
• Filed: 03/03/1976
• Issued: 09/20/1977
• Est. Priority Date: 02/02/1976
• Status: Expired due to Term

• Current Assignee: Intermedics Incorporated
• Original Assignee: ARCO Medical Products Company
• Inventors: Walters, Robert A.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/663,372
• Time in Patent Office: 566 Days
• Field of Search: 128/419 E, 128/419 P, 128/419 PG, 128/419 PT, 128/419 R, 128/421, 128/422, 128/423, 307/265, 307/273, 328/193
• US Class Current: 607/30
• CPC Class Codes: A61N 1/37211 Means for communicating with stimulators

Abstract

An implantable cardiac pacer is instructable to vary the stimulation pulse interval, the stimulation pulse width, the stimulation pulse amplitude, the pacer sensitivity, the refractory period and the mode (demand or asynchronous).

A master parameter control circuit is provided to vary selected parameters of the heart pacer in accordance with an externally applied control signal.

An external control unit produces two sequential series of pulses, the first series being an access comprising at least one digital "0" state which must be detected by an access code detecting circuit within the master parameter control before the following parameter code will be accepted to vary the pacer parameters. The parameter code, generated subsequently to the access code, determines the selected set of pacer parameters, and can be selected from external controls upon the external control unit.

The master parameter control circuit includes means for recognizing the access code to enable the master parameter control circuit to only thereafter accept the selected parameter code. The entire parameter code must then be entirely received prior to changing the pacer parameters.

Claims

1. An implantable cardiac pacer for connection to heart contacting electrodes comprising:

means for generating a plurality of clock pulses within a normal heartbeat interval;

triggerable means for generating a heart stimulation pulse for delivery to said heart electrodes;

means for counting said clock pulses for a stimulation pulse interval to thereafter deliver a trigger signal to said stimulation pulse generating means;

means for counting said clock pulses to a refractory interval count;

means for detecting signals upon the heart electrodes and for generating a signal in response thereto to reinitiate the count of said refractory interval counting means;

means responsive to said detected heart electrode signal after said refractory interval count for resetting said stimulation counter;

means for independently adjusting the width of said stimulation pulse, the amplitude of said stimulation pulse, the refractory interval count, the stimulation pulse interval, the sensitivity of said detecting means, and the resetting of said stimulation counter;

means for receiving externally transmitted parameter control signals;

register means connected to said receiving means into which said parameter control signals are loaded prior to their execution;

memory means connected to receive signals from said register means for storing said parameter control signals for controlling said independent adjusting means;

means operative to load said parameter control signals into said memory means after said parameter control signals are loaded into said register means;

and means interconnecting said memory means to said adjusting means to execute the parameter control signals in said memory means, whereby said stimulation pulse width, stimulation pulse amplitude, refractory interval count, stimulation pulse interval, sensitivity of said detecting means and resetting of said stimulation counter are controlled by said parameter control signals.

2. The pacer of claim 1 further comprising means for generating a unique parameter determining signal at a location remote from said pacer, said signal uniquely identifying a selectible set of pacer operating parameters;

means for transmitting said signal to said pacer;

and means for receiving said signal in said pacer and generating said sequence of parameter control signals in response thereto for storage in said memory means.

3. The pacer of claim 2 wherein said transmitting means comprises means for generating electromagnetic pulses and wherein said means for receiving said signal in said pacer comprises a magnetically actuated reed switch.

4. The pacer of claim 2 wherein said means for generating a signal comprises means for producing a selectible number of electromagnetic pulses correlating in number to a predetermined unique set of pacer parameters.

5. The pacer of claim 2 further comprising an access code detecting circuit responsive to a predetermined sequence of signals preceding said unique parameter determining signal to enable said control signals to be loaded into said memory.

6. The pacer of claim 5 wherein said access code detecting circuit is responsive only to a predetermined access sequence of signals at a particular frequency.

7. The pacer of claim 6 wherein said access code comprises both high and low logic states.

8. The pacer of claim 2 wherein said means for generating said parameter determining signal comprises a clock pulse generator and means responsive to the clock pulses for spacing said parameter determining signals, and wherein said pacer includes clock pulse responsive means to control the reception of said parameter determining signals at a comparable clock frequency.

9. An implantable digital cardiac pacer adapted to deliver stimulation pulses to a heart contacting electrode having externally selectible operating parameters comprising:

a heart stimulation pulse generator for connection to said electrode;

an external instruction device adapted to transmit a train of parameter selection pulses;

means for receiving said train of pulses and for generating a digital signal in response thereto;

memory means for storing said digital signal;

means interconnecting said pulse receiving means and said memory means to permit the loading of said digital signal into said memory means only after said train of pulses is entirely received by said receiving means;

means for varying at least one of the operating parameters of said pulse generator;

and means connecting said memory means and said parameter varying means to enable said parameter varying means to control said at least one operating parameter in response to said digital signal.

10. The pacer of claim 9 further comprising means within said external instruction device for generating an access code signal preceding said train of parameter selection pulses, and wherein said means to control the loading of said digital signal into said memory means further comprises unlatching circuitry means adapted to discriminatingly reject all external signals until said access code has been recognized.

11. The pacer of claim 10 wherein said train of said parameter selection pulses and said access code signal comprise electromagnetic pulses generated by said external instruction device.

12. The pacer of claim 11 wherein said instruction device transmits said electromagnetic pulses at a predetermined frequency, and wherein said receiving means comprises a magnetically responsive reed switch within said pacer to receive said electromagnetic pulses, and further comprising means within said pacer for constraining the loading of said memory means only to said digital signal when generated in response to said electromagnetic pulses of said predetermined frequency.

13. A heart pacer having a pulse generator for delivering stimulation pulses to a heart contacting electrode and having selectible discrete operating parameters, comprising:

means for receiving a train of pulses of number corresponding to a preassigned pacer parameter combination;

means for counting the pulses received to produce a binary signal representing the number of said pulses in said train;

memory means into which said binary signal is loaded;

counting means connected to said memory means to permit said binary signal to be loaded into said memory only after the train of pulses is entirely received;

and control means connected to said memory means to select said operating parameters in said preassigned parameter combination for controlling said pulse generator.

14. The heart pacer of claim 13 further comprising a pulse transmitter for generating a train of pulses at a location remote from the pacer, the number of pulses being selectible to correspond to a preassigned pacer parameter combination.

15. The heart pacer of claim 14 wherein said pulse transmitter generates a train of electromagnetic pulses, and wherein said means for receiving a train of pulses comprises an electromagnetically actuated reed switch.

16. The heart pacer of claim 13 further comprising means connected to said electrode to detect pulses thereon to inhibit said pulse generator in response thereto and means connected to said pacer to control the asynchronous pulse rate, pulse amplitude, and pulse width of said pulse generator and the sensitivity, refractory period and mode of said inhibit means in response to said control means.

17. The heart pacer of claim 13 further comprising latch means to which said train of pulses is applied for disabling said binary signal producing counting means until said latch means receives a predetermined access sequence of pulse.

18. The heart pacer of claim 17 wherein said latch means comprises access recognition circuit means for recognizing a predetermined access code having at least one inverted pulse.

19. For use in a digital heart pacer of the type which receives externally transmitted pulses, a "one shot" digital pulse generator for producing a pulse of controlled amplitude and width upon the application of said received pulse, comprising:

a source of digital "high" and "low" states;

a clock pulse generator;

first and second flip-flop means each having a data input terminal, an output terminal, an inverted output terminal, a clock terminal operable to produce a next state output in accordance with the present state input, and a reset terminal;

said received pulse being conducted to the clock input of said first flip-flop, said data input terminal of said first flip-flop being connected to a digital "high" state, and the output of said first flip-flop being connected to the data input of said second flip-flop, and additionally defining the output of said digital "one shot" generator;

counter means having a clock input and an output which changes state after the application of a predetermined number of clock pulses to the clock input, and a reset terminal to initialize said counter;

said counter being reset by the signal on the inverted output terminal of said first flip-flop, and providing a signal upon said output terminal to said clock terminal of said second flip-flop, said counter receiving clock pulses from a clock generator upon its clock input terminal;

the output from said second flip-flop being connected to reset said first and second flip-flops to an initial state;

whereby upon the application of a received pulse to said first flip-flop, an output is presented upon its output terminals which is of predetermined amplitude, continuing until said first and second flip-flops are reset as controlled by the count output of said counter.

20. A circuit for controlling the parameters of an implantable cardiac pacer responsive to remote signals having a first portion defining an access code having both high and low logic states, and a second portion defining a parameter controlling code comprising,

means for receiving said remote signals,

access code recognizing circuit means for signalling the reception of said access code having both high and low logic states,

means for counting said second portion of said remote signals to produce a digital representation thereof,

gate means receiving said second portion for passing said second portion only after said access code recognizing circuit signals reception of said access code,

storage means for loading thereinto said digital representation of said second portion from said counting means for controlling the pacer parameters,

means for controlling the pacer parameters in accordance with said parameter controlling code in response to said digital representation loaded into said storage means.

21. The circuit of claim 20 further comprising timing means including clock means for generating timing pulses, and second gate means connected to receive said timing pulses and said remote signals to pass said remote signals to said second portion receiving gate means and said access code recognizing circuit means only in conjunction with said timing pulses.

22. The circuit of claim 21 further comprising means for timing the reception of said second portion to only thereafter permit said digital representation to be loaded into said storage means.

23. The circuit of claim 20 further comprising means for timing the reception of said second portion to only thereafter permit said digital representation to be loaded into said storage means.

24. A circuit for controlling after the reception of a cardiac signal or a stimulation signal the refractory period of an implantable digital cardiac pacer having a resettable stimulation pulse interval controlling means comprising:

means for producing a first reset signal upon detecting a cardiac or a stimulation signal,

a source of clock pulses,

a counter resettable by said first reset signal for counting said clock pulses after the occurrence of said first reset signal to produce at least first and second output signals at predetermined clock pulse counts,

signal selection means responsive to a digital signal applied to an input thereof and having inputs to which said first and second output signals are applied to produce a selected signal determined by said digital signal,

means for generating said digital signal in response to a remotely generated control signal, and

means to produce a second reset signal for resetting said stimulation pulse interval controlling means, said resetting signal producing means being enabled by said selected signal to thereafter produce said second signal upon the reception of a next following first reset signal.