Method and apparatus for dual chamber cardiac pacing

• US 5,507,782 A
• Filed: 03/17/1994
• Issued: 04/16/1996
• Est. Priority Date: 03/17/1994
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Hess, Michael F., Kieval, Robert S.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/214,933
• Time in Patent Office: 761 Days
• Field of Search: 607/9, 607/28
• US Class Current: 607/9
• CPC Class Codes: A61N 1/056 Transvascular endocardial electrode systems
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/3682 with a variable atrioventricular delay
• CPC Class Codes: A61N 1/3712 Auto-capture, i.e. automatic adjustment of the stimulation threshold

Abstract

A dual chamber pacemaker and a method of employing the pacemaker to accomplish atrial synchronized ventricular pacing with complete ventricular capture by control of the A-V escape intervals of the pacer. The maximum A-V escape interval effective to accomplish complete ventricular capture is determined and compared to intrinsic A-V conduction time to derive an offset interval. The offset interval is subtracted from the initially measured conduction time to select initial A-V escape interval durations and is subtracted from A-V conduction times measured after implant of the pacemaker to automatically adjust A-V escape interval durations of the pacemaker to maintain complete ventricular capture.

Claims

1. A method of pacing a heart, comprising:

detecting atrial and ventricular depolarizations;

measuring atrial--ventricular conduction time of said heart;

delivering ventricular pacing pulses capable of completely capturing said heart'"'"'s ventricles absent concurrent spontaneous depolarizations of said ventricles;

determining a time interval following an atrial depolarization of said heart, such that a ventricular pacing pulse delivered at expiration of said time interval results in complete ventricular capture of said heart;

deriving a first offset interval based on relative durations of said determined time interval and said measured atrial--ventricular conduction time;

defining A-V escape intervals following atrial depolarizations;

delivering ventricular pacing pulses at the expirations of said A-V escape intervals absent ventricular depolarizations during said A-V escape intervals;

measuring atrial--ventricular conduction time of a ventricular depolarization occurring within a said A-V escape interval; and

defining duration of a subsequent said A-V escape interval based on said first offset interval and said atrial--ventricular conduction time measured within said A-V escape interval.

8. A method according to claim 1 or claim 2, further comprising the steps of sensing spontaneous atrial depolarizations and delivering atrial pacing pulses and wherein said step of defining duration of a subsequent A-V escape interval comprises defining a first A-V escape interval duration to be employed following spontaneous atrial depolarizations and a second A-V escape interval to be employed following delivered atrial pacing pulses.

9. A method according to claim 1 or claim 2, wherein said step of defining duration of a subsequent A-V escape interval comprises determining heart rate and defining duration of a subsequent said A-V escape interval based on said first offset interval, said atrial--ventricular conduction time measured within said extended A-V escape interval, and said determined heart rate.

2. A method of pacing a heart, comprising:

detecting atrial and ventricular depolarizations;

measuring atrial--ventricular conduction time of said heart;

delivering ventricular pacing pulses capable of completely capturing said heart'"'"'s ventricles absent concurrent spontaneous depolarizations of said ventricles;

determining a time interval following an atrial depolarization of said heart, such that a ventricular pacing pulse delivered at expiration of said time interval results in complete ventricular capture of said heart;

deriving a first offset interval based on relative durations of said determined time interval and said measured atrial--ventricular conduction time;

defining an A-V escape intervals following atrial depolarizations;

delivering ventricular pacing pulses at the expirations of said A-V escape intervals absent ventricular depolarizations during said A-V escape intervals;

extending durations of said A-V escape intervals until a ventricular depolarization falls within a said extended A-V escape interval;

measuring atrial--ventricular conduction time of a ventricular depolarization occurring within a said extended A-V escape interval; and

defining duration of a subsequent said A-V escape interval based on said first offset interval and said atrial--ventricular conduction time measured within said extended A-V escape interval.

3. A method according to claim 2, further comprising the step of counting sequentially delivered ventricular pacing pulses and wherein said extending step comprises extending said A-V escape intervals in response to counting a predetermined number of sequentially delivered ventricular pacing pulses.

4. A method according to claim 2, wherein said extending step comprises extending said A-V escape intervals up to a predefined maximum A-V escape interval, and further comprising the step of preventing subsequent extensions of said A-V escape intervals for a period of time in response to failure of a ventricular depolarization to occur within said maximum A-V escape interval.

5. A method of pacing a heart, comprising:

sensing atrial depolarizations;

delivering a ventricular pacing pulse to said heart to induce complete ventricular capture;

"determining a ventricular depolarization waveform caused by said ventricular pacing pulse and indicative of complete ventricular capture;

"

defining A-V escape intervals following atrial depolarizations;

delivering ventricular pacing pulses at expirations of said A-V escape intervals;

varying durations of said A-V intervals while monitoring waveforms of ventricular depolarizations following said ventricular pacing pulses to define an A-V escape interval such that a ventricular pacing pulse delivered at expiration of said defined A-V escape interval results in complete ventricular capture of said heart; and

employing said defined A-V escape interval to control durations of subsequent A-V escape intervals.

6. A method according to claim 5, wherein said employing step comprises employing said defined A-V escape interval as subsequent A-V escape intervals.

7. A method according to claim 5, further comprising the step of measuring atrial--ventricular conduction time of said heart, and wherein said employing step comprises the steps of:

deriving a first offset interval based on relative durations of said defined A-V escape interval and said measured atrial--ventricular conduction time;

measuring atrial--ventricular conduction time of a ventricular depolarization occurring within a first one of said subsequent A-V escape intervals; and

defining duration of a second, later one of said subsequent A-V escape intervals based on said first offset interval and said atrial--ventricular conduction time measured within first one of said subsequent A-V escape intervals.

10. Apparatus for pacing a heart, comprising:

means for sensing atrial depolarizations;

means for defining a first offset interval;

means for defining A-V escape intervals following atrial depolarizations;

means for sensing ventricular depolarizations of said heart;

means for delivering ventricular pacing pulses at the expirations of said A-V escape intervals in the absence of ventricular depolarizations during said A-V escape intervals;

means for extending durations of said A-V escape intervals until a ventricular depolarization falls within a said extended A-V escape interval;

means for measuring atrial--ventricular conduction time of a sensed ventricular depolarization occurring within a said extended A-V escape interval; and

means for defining duration of a subsequent said A-V escape interval by subtracting said first offset interval and said atrial--ventricular conduction time measured within said extended A-V escape intervail;

wherein said means for extending said A-V escape intervals comprises means for extending said A-V escape intervals up to a predefined maximum A-V escape interval, and further comprises means for preventing subsequent extensions of said A-V escape intervals for a period of time in response to failure of a ventricular depolarization to occur within said maximum A-V escape interval.

11. A apparatus according to claim 10, further comprising means for counting sequentially delivered ventricular pacing pulses and wherein said means for extending said A-V escape intervals comprises extending said A-V escape intervals in response to counting a predetermined number of sequentially delivered ventricular pacing pulses.

12. Apparatus according to claim 10, wherein said means for extending said A-V escape intervals comprises means for extending said A-V escape intervals up to a predefined maximum A-V escape interval, and further comprises means for preventing subsequent extensions of said A-V escape intervals for a period of time in response to failure of a ventricular depolarization to occur within said maximum A-V escape interval.

13. Apparatus according to claim 10, further comprising means for delivering atrial pacing pulses and wherein said means for defining duration of a subsequent A-V escape interval comprises means for defining a first A-V escape interval duration to be employed following a sensed spontaneous atrial depolarizations and means for defining a second A-V escape interval to be employed following delivered atrial pacing pulses.

14. Apparatus according to claim 10, wherein said means for defining duration of a subsequent A-V escape interval comprises means for determining heart rate and means for defining duration of a subsequent said A-V escape interval based on said first offset interval, said atrial--ventricular conduction time measured within said extended A-V escape interval, and said determined heart rate.

15. Apparatus for pacing a heart, comprising:

means for sensing atrial and ventricular depolarizations;

means for measuring atrial--ventricular conduction time of said heart;

means for delivering ventricular pacing pulses capable of completely capturing said heart'"'"'s ventricles absent concurrent spontaneous depolarizations of said ventricles;

means for determining a time interval following an atrial depolarization of said heart, such that a said ventricular pacing pulse delivered at expiration of said time interval results in complete ventricular capture of said heart;

means for deriving a first offset interval based on relative durations of said determined time interval and said measured atrial--ventricular conduction time;

means for defining A-V escape intervals following atrial depolarizations;

means for sensing ventricular depolarizations of said heart;

delivering ventricular pacing pulses at the expirations of said A-V escape intervals absent sensed ventricular depolarizations during said A-V escape intervals;

means for measuring atrial--ventricular conduction time of a ventricular depolarization occurring within a said A-V escape interval; and

means for defining duration of a subsequent said A-V escape interval based on said first offset interval and said atrial--ventricular conduction time measured within said A-V escape interval.

16. Apparatus for pacing a heart, comprising:

means for sensing atrial and ventricular depolarizations;

means for measuring atrial--ventricular conduction time of said heart;

means for delivering ventricular pacing pulses capable of completely capturing said heart'"'"'s ventricles absent concurrent spontaneous depolarizations of said ventricles;

means for determining a time interval following an atrial depolarization of said heart, such that a ventricular pacing pulse delivered at expiration of said time interval results in complete ventricular capture of said heart;

means for deriving a first offset interval based on relative durations of said determined time interval and said measured atrial--ventricular conduction time;

means for defining an A-V escape intervals following atrial depolarizations;

means for sensing ventricular depolarizations of said heart;

means for delivering ventricular pacing pulses at the expirations of said A-V escape intervals absent ventricular depolarizations during said A-V escape intervals;

means for extending durations of said A-V escape intervals until a sensed ventricular depolarization falls within a said extended A-V escape interval;

means for measuring atrial--ventricular conduction time of a sensed ventricular depolarization occurring within a said extended A-V escape interval; and

means for defining duration of a subsequent said A-V escape interval based on said first offset interval and said atrial--ventricular conduction time measured within said extended A-V escape interval.

17. Apparatus for pacing a heart, comprising:

means for sensing atrial and ventricular depolarizations;

means for delivering a ventricular pacing pulse to said heart to induce complete ventricular capture;

means for delivering ventricular pacing pulses capable of completely capturing said heart'"'"'s ventricles absent concurrent spontaneous depolarizations of said ventricles;

means for monitoring waveforms of ventricular depolarizations;

means for determining a ventricular depolarization waveform indicative of complete ventricular capture;

means for defining A-V escape intervals following atrial depolarizations;

means for delivering said ventricular pacing pulses at expirations of said A-V escape intervals;

means for varying durations of said A-V intervals while monitoring waveforms of ventricular depolarizations following said ventricular pacing pulses;

means responsive to said monitoring means, for identifying a said A-V escape interval duration such that a ventricular pacing pulse delivered at expiration of said identified A-V escape interval duration results in complete ventricular capture of said heart; and

means for employing said identified A-V escape interval duration to define durations of subsequent said A-V escape intervals.

18. Apparatus according to claim 17, wherein said employing means comprises means for employing said identified A-V escape interval duration as a subsequent said A-V escape intervals.

19. Apparatus according to claim 17, further means for measuring atrial--ventricular conduction time of said heart, and wherein said employing means comprises:

means for deriving a first offset interval based on relative durations of said identified A-V escape interval and said measured atrial--ventricular conduction time;

means for measuring atrial--ventricular conduction time of a ventricular depolarization occurring within a first one of said subsequent A-V escape intervals; and

means for defining duration of a second, later one of said subsequent A-V escape intervals based on said first offset interval and said atrial--ventricular conduction time measured within first one of said subsequent A-V escape intervals.