DIGITAL COUNTER DRIVEN PACER

• US 3,557,796 A
• Filed: 03/10/1969
• Issued: 01/26/1971
• Est. Priority Date: 03/10/1969
• Status: Expired due to Term

• Current Assignee: Telectronics Incorporated
• Original Assignee: Gomer L. Davies, John W. Keller Jr, Reese S. Terry Jr
• Inventors: Keller, John W. Jr., Terry, Reese S. Jr., Davies, Gomer L.
• Application Number:
  US04/805,714
• Time in Patent Office: 687 Days
• US Class Current: 607/9
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/368 comprising more than one electrode co-operating with different heart regions A61N1/3622, A61N1/3627 take precedence

Abstract

The cardiac pacer disclosed herein employs a digital counter driven by a relatively high frequency oscillator to time intervals which simulate various cardiac functions. When allowed to cycle repetitively, the counter provides a relatively slow, fixed rate mode of operation. However, the counter may be reset under certain conditions by ventricular signals to provide a demand mode of operation and by atrial signals under certain other conditions to provide a so-called synchronized mode of operation. Noise rejection circuitry is also disclosed.

Claims

1. Cardiac pacer apparatus comprising:

an oscillator providing a pulsating signal at a preselected frequency, which preselected frequency is a relatively large multiple of a normal heart beat rate;

a cyclically operating digital counter means for counting the pulsations of said pulsating signal; and

means controlled by said counter for generating a cardiac stimulating potential when said counter reaches a predetermined count.

2. Apparatus as set forth in claim 1 wherein said means for generating said cardiac stimulating potential includes means for initiating the generation of said potential at the start of one cycle of said pulsating signal and for terminating the generation of said potential at the start of the next cycle of said pulsating signal.

3. Apparatus as set forth in claim 1 further comprising:

means for detecting cardiac signals generated during a heartbeat; and

means responsive to such detected cardiac signals for setting said counter to a starting point count which precedes said predetermined count by a number corresponding to a preselected maximum interval between successive heartbeats whereby a stimulating potential is generated only if said preselected maximum interval elapses between heartbeats.

4. Apparatus as set forth in claim 3 including means controlled by said counter for inhibiting resetting of said counter when the count held thereby is between said starting point count and a count which is intermediate said starting point count and said predetermined count, the difference between said starting point count and the intermediate count corresponding to a preselected refractory delay period.

5. Apparatus as set forth in claim 4 further comprising:

a second digital counter for counting signals detected by said detecting means;

means controlled by said second digital counter For inhibiting resetting of the first said counter between said intermediate count and said predetermined count if more than a predetermined number of detected signals are counted by said second counter during the interval between a count which is intermediate said starting point count and said intermediate count whereby rapidly repeated electrical noise signals reaching said detecting means are ineffective to prevent generation of a stimulating potential at said predetermined count.

6. Apparatus as set forth in claim 1 further comprising means for detecting atrial signals;

and means responsive to such detected atrial signals for setting said counter to a starting point count, which precedes said predetermined count by a number corresponding to a preselected A-V delay whereby stimulating potentials are generated in synchronously timed relationship to said atrial signals.

7. Apparatus as set forth in claim 6 including means controlled by said counter for inhibiting resetting of said counter when the count held thereby is between said predetermined count and a subsequent count, the difference between said predetermined count and said subsequent count corresponding to a predetermined refractory delay period.

8. Apparatus as set forth in claim 7 further comprising:

a second digital counter for counting signals detected by said detecting means;

means controlled by said second digital counter for inhibiting resetting of the first said counter between said subsequent count and said starting point count if more than a predetermined number of detected signals are counted by said second counter during the interval between;

a count which is intermediate said predetermined count and said subsequent count; and

said subsequent count, whereby rapidly repeated electrical noise signals reaching said detecting means are ineffective to prevent generation of a stimulating potential at said predetermined count.

9. Cardiac pacer apparatus comprising:

an oscillator providing a pulsating signal at a preselected frequency, which preselected frequency is a relatively large multiple of a normal heart beat rate;

a cyclically operating digital counter means for counting the pulsations of said pulsating signal;

means for initiating the generation of a cardiac stimulating potential starting at a predetermined count and for terminating the generation of said potential at a subsequent count;

means for detecting cardiac signals generated during a heartbeat;

means for setting said counter to a starting point count which precedes said predetermined count by a number corresponding to a preselected maximum interval between successive heartbeats in response to cardiac signals which are detected after a count which is intermediate said starting point count and said predetermined count, the difference between said starting point count and the intermediate count corresponding to a preselected refractory delay period.

10. Apparatus as set forth in claim 9 further comprising:

a second digital counter for counting signals detected by said detecting means;

means controlled by said second digital counter for inhibiting resetting of the first said counter between said intermediate count and said predetermined count if more than a predetermined number of detected signals are counted by said second counter during the interval between;

a count which is intermediate said starting point count and said intermediate count; and

the first said intermediate count, whereby rapidly repeated electrical noise signals reaching said detecting means are ineffective to prevent generation of a stimulating potential at said predetermined count.

11. Cardiac pacer apparatus comprising:

an oscillator providing a pulsating signal at a preselected frequency, which preselected frequency is a relatively large multiple of a normal heartbeat rate;

a cyclically operating digital counter means for counting the pulsations of said pulsating signal;

means for initiatIng the generation of a cardiac stimulating potential starting at a predetermined count and for terminating the generation of said potential at a subsequent count;

means for detecting atrial signals;

means for setting said counter to a starting point count which precedes said predetermined count by a number corresponding to a preselected A-V delay in response to atrial signals which are detected after a subsequent count which is after said predetermined count by a number corresponding to a preselected refractory delay period.

12. Apparatus as set forth in claim 7 further comprising:

a second digital counter for counting signals detected by said detecting means;

means controlled by said second digital counter for inhibiting resetting of the first said counter between said subsequent count and said starting point count if more than a predetermined number of detected signals are counted by said second counter during the interval between;

a count which is intermediate said predetermined count and said subsequent count; and

said subsequent count, whereby rapidly repeated electrical noise signals reaching said detecting means are ineffective to prevent generation of a stimulating potential at said predetermined count.