Algorithm for the automatic determination of optimal pacing intervals

• US 20060271117A1
• Filed: 05/24/2005
• Published: 11/30/2006
• Est. Priority Date: 05/24/2005
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Rueter, John C., Cho, Yong K., Burnes, John E., Mongeon, Luc R., Zilinski, Jodi, Igel, David A., Stone, Harold E.
• Granted Patent: US 7,711,423 B2
• Time in Patent Office: Days
• US Class Current: 607/9
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

Impedance, e.g. sub-threshold impedance, is measured across the heart at selected cardiac cycle times as a measure of chamber expansion or contraction. One embodiment measures impedance over a long AV interval to obtain the minimum impedance, indicative of maximum ventricular expansion, in order to set the AV interval. Another embodiment measures impedance change over a cycle and varies the AV pace interval in a binary search to converge on the AV interval causing maximum impedance change indicative of maximum ventricular output. Another method varies the right ventricle to left ventricle (VV) interval to converge on an impedance maximum indicative of minimum cardiac volume at end systole. Another embodiment varies the VV interval to maximize impedance change. Other methods vary the AA interval to maximize impedance change over the entire cardiac cycle or during the atrial cycle.

Claims

1. A method for setting a pacing interval, the method comprising:

adjusting the pacing interval to a plurality of settings;

measuring an impedance signal sensitive to changes in cardiac volume;

determining the pacing interval setting associated with a maximum impedance measurement; and

setting the pacing interval to the pacing interval setting associated with the maximum impedance measurement.

2. The method as in claim 1, wherein the pacing interval is an atrial-to-atrial (AA) interval.

3. The method as in claim 1, wherein the impedance measuring occurs during the atrial cycle.

4. The method as in claim 3, wherein the impedance measuring includes selecting impedance measuring electrodes for measuring an impedance signal sensitive to changes in atrial volume.

5. The method as in claim 1, wherein the maximum impedance measurement is a measurement of a maximum change in impedance.

6. The method as in claim 1, wherein adjusting the pacing interval settings includes selecting a plurality of pacing interval settings that converge on the maximum impedance measurement in decreasing time intervals.

7. The method as in claim 6, wherein the selecting pacing interval settings is performed according to a binary searching method for converging on the maximum impedance measurement.

8. The method as in claim 1, wherein the measuring the impedance signal includes measuring the impedance signal at a plurality of time points beginning near an A-pace event until near a next V-event.

9. The method as in claim 1, wherein the measuring the impedance signal includes measuring the impedance signal at a plurality of time points beginning near a V-event until near a next A-event.

10. The method as in claim 1, wherein the measuring the impedance signal further includes:

sensing a respiration signal;

measuring the impedance signal at a time point corresponding to substantially unchanged impedance due to respiration.

11. The method as in claim 10, wherein the sensing includes sensing respiration movement using an accelerometer.

12. The method as in claim 10, wherein the sensing includes selecting a set of impedance measuring electrodes for measuring an impedance signal sensitive to respiration.

13. A system, comprising:

at least one pair of impedance sensing electrodes;

an impedance measurement unit for measuring the impedance between the electrode pair;

a control unit for setting a pacing interval to a plurality of settings and for causing the impedance measurement unit to perform an impedance measurement during at least one cardiac cycle for each of the plurality of pacing interval settings; and

a processing unit for receiving the impedance measurements and for determining the pacing interval setting associated with a maximum impedance measurement.

14. The system according to claim 13 wherein the control unit receives from the processing unit the pacing interval setting during which the maximum impedance was measured and the control unit sets the pacing interval substantially equal to the pacing interval setting.

15. The system according to claim 13 wherein the impedance sensing electrodes are adapted for implantation in a patient'"'"'s body and the impedance measurement unit is included in an implantable medical device.

16. The system according to claim 13 wherein the control unit and the processing unit are included in an implantable medical device.

17. The system according to claim 13 wherein at least one of the control unit and the processing unit are included in an external programming unit.

18. The system according to claim 13 further including an external programming unit including a display unit for displaying instructions to a physician for directing a patient to perform steps that cause the patient to achieve a predetermined physiological condition.

19. The system according to claim 13 further including a physiological sensor for detecting a physiological condition and wherein the control unit causes the impedance measuring unit to perform impedance measurements when the physiological sensor detects a predetermined physiological condition.

20. The system according to claim 19 wherein the predetermined physiological condition is any combination of the physiological conditions selected from the group of:

a heart rate condition, a respiration condition, a posture condition, and a physical activity condition.

21. A system, comprising:

means for varying a pacing interval setting;

means for measuring an impedance signal sensitive to changes in cardiac volume during at least one cardiac cycle for each pacing interval setting;

means for determining the pacing interval setting associated with a maximum impedance measurement;

means for setting the pacing interval to the determined pacing interval setting associated with the maximum impedance measurement.

22. A computer readable medium containing instructions that when implemented in a medical device, cause the device to:

adjust a pacing interval to a plurality of pacing interval settings;

measure an impedance signal at least one time point during at least one cardiac cycle for each of the pacing interval settings; and

determine the pacing interval setting associated with a maximum impedance measurement.

23. The computer readable medium of claim 22, further causing the device to set the pacing interval to the pacing interval setting associated with the maximum impedance measurement.

24. The computer readable medium of claim 22 wherein the maximum impedance measurement is a maximum change in impedance.

25. The computer readable medium of claim 22 wherein the pacing interval is an atrial-to-atrial (AA) interval.

26. The computer readable medium of claim 22 wherein the impedance signal is substantially sensitive to changes in atrial volume.