Detection of cardiac evoked potentials

• US 4,858,610 A
• Filed: 02/08/1988
• Issued: 08/22/1989
• Est. Priority Date: 12/11/1985
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Telectronics Incorporated
• Inventors: Schroeppel, Edward A., Callaghan, Frank J.
• Primary Examiner(s): JAWORSKI, FRANCIS J
• Application Number:
  US07/157,084
• Time in Patent Office: 561 Days
• Field of Search: 128/419 P, 128/419 PG, 128/419 D
• US Class Current: 607/13
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/3712 Auto-capture, i.e. automatic adjustment of the stimulation threshold
• CPC Class Codes: A61N 1/3716 with reduction of residual polarisation effects

Abstract

Automatic detection of cardiac pacer evoked potentials may be obtained through a cardiac pacer lead positioned in a heart chamber. An electrical stimulus is emitted in unipolar mode from a first electrode to stimulate muscular contraction. The cardiac electrical activity evoked by the stimulus is then detected in unipolar mode by a second electrode which is spaced from the first electrode and free of electrical connection thereto. Accordingly, signal interference caused by residual polarization of the first electrode is suppressed. The natural cardiac electrical activity is sensed in a bipolar mode, and the pulse is inhibited if a heartbeat is detected within an alert period.

Claims

1. The method of cardiac pacing and sensing which comprises the steps of:

providing a cardiac pacing lead having a first electrode carried on the distal end of said lead and a second electrode carried by the lead and spaced from said first electrode and free of electrical connection thereto;

positioning said lead in a heart chamber;

periodically emitting an electrical stimulus, pulse in a unipolar mode, from said first electrode to stimulate cardiac muscular contraction; and

detecting in a unipolar mode, an electric potential response evoked by said pulse, by said second electrode, whereby signal interference caused by residual polarization of said first electrode is suppressed.

2. The method of claim 1 in which said pacer lead connects to pacer power and circuit means sealed in a metal can, said metal can serving as reference electrode to said first and second electrodes.

3. The method of claim 1 in which, following said pulse, an output capacitor is discharged through the heart muscle for 5 to 15 milliseconds to cause residual charge to depart said first electrode.

4. The method of claim 1 in which pairs of said first and second electrodes are carried on separate lead sections, said electrode pairs being all in electrical communication with pacer power and circuit means sealed in a metal can, said metal can serving as a reference electrode to said first and second electrodes, one of said pairs of electrodes being installed in an atrium and another pair in a ventricle.

5. The method of claim 1 in which said first and second electrodes are spaced at least about 0.5 cm. apart.

6. The method of cardiac pacing and sensing which comprises the steps of:

providing a cardiac pacing lead having a first electrode carried on the distal end of said lead and a second electrode carried by the lead and spaced from said first electrode and free of electrical connection thereto;

positioning said lead in a heart chamber;

periodically emitting an electrical stimulus pulse from said first electrode to stimulate cardiac muscular contraction and

detecting, in a unipolar mode, an electric potential response evoked by said pulse, by said second electrode, whereby signal interference caused by residual polarization of said first electrode is suppressed;

said second electrode being activated at a predetermined time interval after said electrical stimulus, the duration of said activation being about 10 to 50 milliseconds, whereby said evoked response can be detected and selected from other heart electrical activity.

7. The method of claim 6 in which, at a predetermined interval before said electrical stimulus pulse and while the evoked response is not being detected, a circuit is activated including said first and second electrodes in bipolar relation to identify heart electrical activity associated with heartbeat generation, and emission of said electrical stimulus pulse is inhibited upon sensing of said heart electrical activity.

8. A method of cardiac pacing and sensing which comprises providing a cardiac pacing lead having a first electrode carried on the distal end of said lead and a second electrode carried by the lead and spaced from said first electrode and free of electrical connection thereto, said second electrode being in the form of a ring carried by said lead and being spaced at least about 0.5 cm from said first electrode, periodically emitting an electrical stimulus pulse in a unipolar mode, from said first electrode positioned in a heart chamber to stimulate cardiac muscular contraction, and detecting an electric potential response evoked by said pulse, in a unipolar mode, by said second electrode, whereby signal interference caused by residual polarization of said first electrode is suppressed.

9. The method of claim 8 in which said pacer lead connects to pacer power and circuit means sealed in a metal can, said metal can serving as a reference electrode to said first and second electrodes.

10. The method of claim 9 in which following said pulse, an output capacitor is discharged through the heart muscle for 5 to 15 milliseconds to cause residual charge to depart said first electrode.

11. The method of claim 9 in which an evoked response sensing circuit including said second electrode is activated at a predetermined time interval after said electrical stimulus pulse, the duration of said activation being about 10 to 50 milliseconds, whereby said evoked response can be detected and selected from other heart electrical activity.

12. The method of cardiac pacing and sensing which comprises providing a cardiac pacing lead having a first electrode carried on the distal end of said lead and a second electrode carried by the lead and spaced from said first electrode and free of electrical connection thereto, said second electrode being in the form of a ring carried by said lead and being spaced at least about 0.5 cm from said first electrode, periodically emitting an electrical stimulus pulse from said first electrode on a cardiac pacer lead positioned in a heart chamber to stimulate cardiac muscular contraction, detecting an electric potential response evoked by said pulse, by said second electrode, whereby signal interference caused by residual polarization of said first electrode is suppressed;

providing pacer power and circuit means sealed in a metal can and serving as a reference electrode to said first and second electrodes;

providing an evoked response sensing circuit including said second electrode, activating said second electrode at a predetermined time interval after said electrical stimulus pulse, the duration of said activation being about 10 to 50 milliseconds, whereby said evoked response can be detected and selected from other heart electrical activity;

activating a circuit to identify heart electrical activity associated with hearbeat generation, and inhibiting the emission of a subsequent electrical stimulus upon sensing of said heart electrical activity.

13. The method of claim 12 in which said first electrode emits said pulse and the second electrode detects said evoked response in unipolar mode.

14. The method of claim 12 in which pairs of first and second electrodes are carried on separate lead sections, said electrode pairs being all in electrical communication with pacer power and circuit means sealed in a metal can, said metal can serving as a reference electrode to said first and second electrodes.

15. The method of claim 14 in which one of said pairs of electrodes is for atrial installation and another pair is for ventricular installation.

16. The method of cardiac pacing and sensing which comprises providing a cardiac pacing lead having a first electrode carried on the distal end of said lead and a second electrode carried by the lead and spaced from said first electrode and free of electrical connection thereto;

positioning said lead in a heart chamber;

periodically emitting an electrical stimulus pulse from said first electrode to stimulate cardiac muscular contraction, said electrical stimulus pulse being emitted from the first electrode in unipolar mode;

sensing the evoked response from the heart muscle by the second electrode in unipolar mode during a predetermined window of time subsequent to said emitting of the pulse of electrical potential;

prior to emitting said electrical stimulus pulse from a first electrode, sensing for electrical signals indicating natural heart contraction in bipolar mode using the first and second electrodes during a predetermined alert period preceding the emission of said electrical stimulus pulse by the first electrode, and if said electrical activity signifying natural heart contraction is sensed, inhibiting the emission of the electrical stimulus pulse.

17. The method of claim 16 in which a third electrode is provided to serve as a reference electrode for the first and second electrodes during emission of the electrical stimulus pulse and during sensing of the evoked response.

18. The method of claim 17 in which pacer power and circuit means are provided sealed in a metal can, said metal can serving as said reference electrode for said first and second electrodes during the emissions of the electrical stimulus pulse and during the sensing of the evoked response.

19. The method of claim 18 in which said first electrode is carried on the distal end of said cardiac pacer lead, and the second electrode is in the form of a ring carried about said lead.

20. The method of claim 19 in which, following said electrical stimulus pulse, an output capacitor is discharged through the heart muscle for 5 to 15 milliseconds to cause residual charge to depart said first electrode.

21. The method of claim 20 in which pairs of first and second electrodes are carried on separate lead sections, said electrode pairs being all in electrical communication with said pacer power and circuit means, one of said pairs of electrodes being installed in an atrium and the other being installed in the ventricle.

22. The method of claim 21 in which said first and second electrodes on a common lead are spaced at least about 0.5 cm. apart.

23. Apparatus for cardiac pacing and sensing which comprises:

a cardiac pacing lead adapted for positioning within a heart chamber, said lead having a first electrode on its distal end and a second electrode spaced from said first electrode;

means for transmitting to said first electrode an electrical stimulus pulse in a unipolar mode, to stimulate cardiac muscular contraction;

sensing means, coupled to said second electrode, for detecting an electric potential response evoked by said electrical stimulus pulse in a unipolar mode;

circuit means permitting said first electrode and said second electrode to be free of electrical connection between each other while transmitting said pulse and while sensing, whereby signal interference caused by residual polarization of said first electrode is suppressed.

24. The apparatus of claim 23 in which said second electrode is in the form of a ring carried about said cardiac pacing lead.

25. The apparatus of claim 23 in which pacer power and circuit means are provided in connection with said pacer lead, said pacer power and circuit means being sealed in a metal can, said metal can serving as a reference electrode to said first and second electrodes.

26. The apparatus of claim 23 in which output capacitor means and control means are provided to provide a discharge path through the heart muscle to intermittently permit residual charge to depart said first electrode.

28. The apparatus of claim 23 including means for detecting heart electrical activity associated with heart muscle contraction, and means for inhibiting said transmitting means upon sensing of said heart electrical activity.

29. The apparatus of claim 23 having a plurality of said pairs of first and second electrodes carried on separate lead sections, said electrode pairs all being in electrical communication with pacer power and circuit means, and reference electrode means provided in electrical communication with said first and second electrodes.

30. The apparatus of claim 29 in which said reference electrode means is a metal can which carries said pacer power and circuit means.

27. Apparatus for cardiac pacing and sensing which comprises:

a cardiac pacing lead adapted for positioning within a heart chamber, said lead having a first electrode on its distal end and a second electrode spaced from said first electrode;

means for transmitting to said first electrode an electrical stimulus pulse to stimulate cardiac muscular contraction;

sensing means, coupled to said second electrode, for detecting, in a unipolar mode, an electric potential response evoked by said electrical stimulus pulse;

circuit means permitting said first electrode and said second electrode to be free of electrical connection between each other while transmitting said pulse and while sensing, whereby signal interference caused by residual polarization of said first electrode is suppressed;

said sensing means including means for activation thereof at a predetermined time interval after activation of the means for transmitting to the first electrode an electrical stimulus pulse and for limiting the duration of activation of said sensing means to about 10 to 50 milliseconds, whereby said evoked response can be detected and selected from other heart electrical activity.

31. Apparatus for cardiac pacing and sensing which comprises:

a cardiac pacing lead adapted for positioning within a heart chamber, said lead having a first electrode on its distal end and a second electrode in the form of a ring spaced from said first electrode;

pacer power and circuit means connected to said pacer lead, and including means for transmitting to said first electrode an electrical stimulus pulse in the unipolar mode to stimulate cardiac muscular contraction;

sensing means coupled to said second electrode, for detecting in a unipolar mode an electric potential response evoked by said pulse; and

circuit means permitting said first electrode and said second electrode to be free of electrical connection between each other while transmitting said pulse and while sensing, whereby signal interference caused by residual polarization of said first electrode is suppressed.

32. The apparatus of claim 31 in which a third electrode is provided to serve as a reference electrode to said first and second electrodes.

33. The apparatus of claim 32 including means for detecting heart electrical activity associated with heart muscle contraction, and means for inhibiting said transmitting means upon sensing of said heart electrical activity.

34. Apparatus for cardiac pacing and sensing which comprises:

a cardiac pacing lead adapted for positioning within a heart chamber, said lead having a first electrode on its distal end and a second electrode in the form of a ring spaced from said first electrode;

pacer power and circuit means provided in connection with said pacer lead, and including means for transmitting to said first electrode an electrical stimulus pulse in a unipolar mode to stimulate cardiac muscular contraction;

sensing means coupled to said electrode, for detecting in a unipolar mode an electric potential response evoked by said pulse;

circuit means permitting said first electrode and said second electrode to be free of electrical connection between each other while transmitting said pulse and while sensing, whereby signal interference caused by residual polarization of said first electrode is suppressed;

means for detecting heart electrical activity associated with heart muscle contraction;

means for inhibiting said transmitting means upon sensing of said heart electrical activity;

said sensing means including means for activation thereof at a predetermined time interval after activation of the transmitting means, and for limiting the duration of activation of said sensing means to about 10 to 50 milliseconds, whereby said evoked response can be detected and selected from other heart electrical activity.

35. The apparatus of claim 34 in which output capacitor means and control means are provided to provide a discharge path through the heart muscle to intermittently permit residual charge to depart said first electrode after transmitting to the first electrode an electrical stimulus.

36. The apparatus of claim 35 in which said pacer power and circuit means is carried in a metal can, said metal can also serving as said reference electrode means.

37. The apparatus of claim 36 having a plurality of said pairs of first and second electrodes, said electrode pairs being all in electrical communication with said pacer power and circuit means.

38. The apparatus of claim 37 in which one of said pairs of electrodes is for atrial installation and another pair is for ventricular installation.

39. The apparatus of claim 38 in which said first and second electrodes are spaced at least about 0.5 cm. apart.

40. Apparatus for cardiac pacing and sensing which comprises:

a cardiac pacing lead adapted for positioning within a heart chamber, said lead having a first electrode on its distal end and a second electrode spaced from said first electrode;

means for transmitting to said first electrode an electrical stimulus pulse in a unipolar mode, to stimulate cardiac muscular contraction.

sensing means, coupled to said second electrode, for detecting an electric potential response evoked by said electrical stimulus pulse in a unipolar mode;

circuit means permitting said first electrode and said second electrode to be free of electrical connection between each other while transmitting said pulse and while sensing, whereby signal interference caused by residual polarization of said first electrode is suppressed;

pacer power means;

one of said pairs of electrodes being for atrial installation and another pair of electrodes being for ventricular installation; and

said first and second electrodes being spaced at least about 0.5 cm. apart.