IMPEDANCE VARIABILITY ANALYSIS TO IDENTIFY LEAD-RELATED CONDITIONS

• US 20090299432A1
• Filed: 07/25/2008
• Published: 12/03/2009
• Est. Priority Date: 06/02/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Metronic Incorporated
• Inventors: Stadler, Robert W., Gunderson, Bruce D., Patel, Amisha S.
• Granted Patent: US 8,644,931 B2
• Time in Patent Office: Days
• US Class Current: 607/28
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/3706 Pacemaker parameters stimulation threshold A61N1/371

Abstract

In general, the disclosure relates to techniques for calculating mean impedance values and impedance variability values to detect a possible condition with a lead or device-lead pathway or connection. In one example, a device may be configured to determine an impedance value for an electrical path based on a plurality of measured impedance values for the electrical path, wherein the electrical path comprises a plurality of electrodes, and to determine an impedance variability value based on at least one of the plurality of measured impedance values. The device may be further configured to determine a threshold value based on the determined impedance value and the impedance variability value, compare a newly measured impedance value for the electrical path to the threshold value, and indicate a possible condition of the electrical path based on the comparison.

Claims

1. A method comprising:

determining an impedance value for an electrical path based on a plurality of measured impedance values for the electrical path, wherein the electrical path comprises a plurality of electrodes for at least one of stimulation or sensing;

determining an impedance variability value based on at least one of the plurality of measured impedance values;

determining a threshold value based on the determined impedance value and the impedance variability value;

comparing a newly measured impedance value for the electrical path to the threshold value; and

indicating a possible condition of the electrical path based on the comparison.

2. The method of claim 1, wherein determining the impedance value comprises:

measuring the plurality of measured impedance values for the electrical path at defined points in time during a time interval; and

determining the impedance value based on at least one of the plurality of measured impedance values measured during the time interval.

3. The method of claim 1, further comprising:

determining a second impedance value for a second electrical path based on a second plurality of measured impedance values for the second electrical path, wherein the second electrical path comprises a plurality of electrodes for at least one of patient stimulation or sensing;

determining a second impedance variability value based on at least one of the second plurality of measured impedance values;

determining a second threshold value based on the second determined impedance value and the second impedance variability value;

comparing a newly measured impedance value for the second electrical path to the second threshold value; and

indicating a possible condition of the second electrical path based on the comparison to the second threshold value.

4. The method of claim 1, further comprising:

determining multiple impedance values based on a plurality of initially measured impedance values for the electrical path over a defined time period to obtain an adapted value of the determined impedance value; and

determining multiple impedance variability values based on differences between the plurality of initially measured impedance values and the multiple determined impedance values over the defined time period to obtain an adapted value of the impedance variability value.

5. The method of claim 1, wherein indicating the possible condition comprises generating an indication to a user of the possible condition.

6. The method of claim 1, wherein:

determining the impedance value comprises determining a mean maximum impedance value based on a plurality of measured maximum impedance values;

determining the impedance variability value comprises determining a maximum impedance variability value based a difference between at least one of the plurality of measured maximum impedance values and the mean maximum impedance value at a particular point in time;

determining the threshold value comprises determining a maximum threshold value based on the mean maximum impedance value and the maximum impedance variability value; and

comparing the newly measured impedance value comprises comparing a newly measured maximum impedance value to the maximum threshold value.

7. The method of claim 6, wherein comparing the newly measured maximum impedance value to the maximum threshold value comprises determining whether the newly measured maximum impedance value exceeds the maximum threshold value.

12. The method of claim 1, further comprising:

constraining the impedance variability value based on the determined impedance value.

13. The method of claim 1, further comprising:

determining an impedance range value for the electrical path based on a plurality of difference ranges between maximum and minimum impedance values;

determining an impedance range variability value based on a difference between the determined impedance range value and at least one of the plurality of difference ranges;

determining a threshold range value based on the determined impedance range value and the impedance range variability value; and

comparing newly measured maximum and minimum impedance values for the electrical path to the threshold range value,

wherein indicating the possible condition of the electrical path is further based on the comparison of the newly measured maximum and minimum impedance values to the threshold range value.

15. The method of claim 1, wherein at least one of the plurality of electrodes is located on an implantable medical lead coupled to an implantable medical device.

16. The method of claim 1, wherein determining the impedance variability value comprises determining the impedance variability value based on a difference between the at least one of the plurality of measured impedance values and the determined impedance value at a particular point in time.

8. The method of 1, further comprising:

when the newly measured impedance value is below the threshold value, determining an updated impedance variability value based on the impedance variability value and a difference between the determined impedance value and the newly measured impedance value, such that impedance variability values may adapt over time; and

when the newly measured impedance value is below the threshold value, determining an updated impedance value based on the determined impedance value and the newly measured impedance value, such that determined impedance values may adapt over time.

9. The method of claim 8, further comprising:

repeating, over multiple time periods, the determining of the impedance value, the determining of the impedance variability value, the determining of the threshold value, the comparing of the newly measured impedance value to the threshold value, the determining of the updated impedance variability value, and the determining of the updated impedance value.

10. The method of claim 9, wherein indicating the possible condition occurs when multiple newly measured impedance values have crossed the threshold value during the multiple time periods.

11. The method of claim 10, wherein when the multiple newly measured impedance values have crossed the threshold value a defined number of times, the method further comprises:

determining multiple impedance variability values based on differences between a plurality of subsequently measured impedance values and the determined impedance value over a defined time period to obtain a re-adapted value of the impedance variability value.

14. The method of 13, further comprising:

determining an updated impedance range variability value based on the impedance range variability value and a difference between the determined impedance range value and the newly measured maximum and minimum impedance values, such that impedance range variability values may adapt over time; and

determining an updated impedance range value based on the determined impedance range value and the newly measured maximum and minimum impedance values, such that determined impedance range values may adapt over time.

17. An implantable medical device comprising:

a module configured to measure impedance values for an electrical path associated with at least one implantable lead, wherein the electrical path comprises a plurality of electrodes for at least one of patient stimulation or sensing; and

a processor configured to;

determine an impedance value for the electrical path based on a plurality of measured impedance values for the electrical path;

determine an impedance variability value based on at least one of the plurality of measured impedance values;

determine a threshold value based on the determined impedance value and the impedance variability value;

compare a newly measured impedance value for the electrical path to the threshold value; and

indicate a possible condition of the electrical path based on the comparison.

18. The implantable medical device of claim 17, further comprising a stimulation generator configured to deliver stimulation via the at least one implantable lead, wherein at least one of the plurality of electrodes is located on the at least one implantable lead.

19. The implantable medical device of claim 17, wherein the processor is configured to determine the impedance value at least by measuring the plurality of measured impedance values for the electrical path at defined points in time during a time interval and determining the impedance value based on at least one of the plurality of measured impedance values measured during the time interval.

20. The implantable medical device of claim 17, wherein the processor is further configured to:

determine a second impedance value for a second electrical path based on a second plurality of measured impedance values for the second electrical path, wherein the second electrical path comprises a plurality of electrodes for at least one of patient stimulation or sensing;

determine a second impedance variability value based on at least one of the second plurality of measured impedance values;

determine a second threshold value based on the second determined impedance value and the second impedance variability value;

compare a newly measured impedance value for the second electrical path to the second threshold value; and

indicate a possible condition of the second electrical path based on the comparison to the second threshold value.

21. The implantable medical device of claim 17, wherein the processor is further configured to:

determine multiple impedance values based on a plurality of initially measured impedance values for the electrical path over a defined time period to obtain an adapted value of the determined impedance value; and

determine multiple impedance variability values based on differences between the plurality of initially measured impedance values and the multiple determined impedance values over the defined time period to obtain an adapted value of the impedance variability value.

22. The implantable medical device of claim 17, wherein the processor is configured to generate an indication to a user of the possible condition.

23. The implantable medical device of claim 17, wherein:

the processor is configured to determine the impedance value at least by determining a mean maximum impedance value based on a plurality of measured maximum impedance values;

the processor is configured to determine the impedance variability value at least by determining a maximum impedance variability value based on a difference between at least one of the plurality of measured maximum impedance values and the mean maximum impedance value at a particular point in time;

the processor is configured to determine the threshold value at least by determining a maximum threshold value based on the mean maximum impedance value and the maximum impedance variability value; and

the processor is configured to compare the newly measured impedance value at least by comparing a newly measured maximum impedance value to the maximum threshold value.

24. The implantable medical device of claim 23, wherein the processor is configured to compare the newly measured maximum impedance value to the maximum threshold value at least by determining whether the newly measured maximum impedance value exceeds the maximum threshold value.

29. The implantable medical device of claim 17, wherein the processor is further configured to constrain the impedance variability value based on the determined impedance value.

30. The implantable medical device of claim 17, wherein the processor is further configured to:

determine an impedance range value for the lead based on a plurality of difference ranges between maximum and minimum impedance values;

determine an impedance range variability value based on a difference between the determined impedance range value and at least one of the plurality of difference ranges;

determine a threshold range value based on the determined impedance range value and the impedance range variability value; and

compare newly measured maximum and minimum impedance values for the electrical path to the threshold range value,

wherein the processor is further configured to indicate the possible condition of the electrical path based on the comparison of the newly measured maximum and minimum impedance values to the threshold range value.

32. The implantable medical device of claim 17, wherein the processor is configured to determine the impedance variability value at least by determining the impedance variability value based on a difference between the at least one of the plurality of measured impedance values and the determined impedance value at a particular point in time.

25. The implantable medical device of 17, wherein the processor is further configured to:

determine an updated impedance variability value based on the impedance variability value and a difference between the determined impedance value and the newly measured impedance value when the newly measured impedance value is below the threshold value, such that impedance variability values may adapt over time; and

determine an updated impedance value based on the determined impedance value and the newly measured impedance value when the newly measured impedance value is below the threshold value, such that determined impedance values may adapt over time.

26. The implantable medical device of claim 25, wherein the processor is further configured to:

repeat, over multiple time periods, the determining of the impedance value, the determining of the impedance variability value, the determining of the threshold value, the comparing of the newly measured impedance value to the threshold value, the determining of the updated impedance variability value, and the determining of the updated impedance value.

27. The implantable medical device of claim 26, wherein the processor is configured to indicate the possible condition when multiple newly measured impedance values have crossed the threshold value during the multiple time periods.

28. The implantable medical device of claim 27, wherein when the multiple newly measured impedance values have crossed the threshold value a defined number of times, the processor is further configured to determine multiple impedance variability values based on differences between a plurality of subsequently measured impedance values and the determined impedance value over a defined time period to obtain a re-adapted value of the impedance variability value.

31. The implantable medical device of 30, wherein the processor is further configured to:

determine an updated impedance range variability value based on the impedance range variability value and a difference between the determined impedance range value and the newly measured maximum and minimum impedance values, such that impedance range variability values may adapt over time; and

determine an updated impedance range value based on the determined impedance range value and the newly measured maximum and minimum impedance values, such that determined impedance range values may adapt over time.

33. A system comprising:

a module configured to receive impedance measurement values for an electrical path associated with at least one lead, wherein the electrical path comprises a plurality of electrodes for at least one of patient stimulation or sensing; and

one or more processors configured to;

determine an impedance value for the electrical path based on a plurality of measured impedance values for the electrical path;

determine an impedance variability value based on at least one of the plurality of measured impedance values;

determine a threshold value based on the determined impedance value and the impedance variability value;

compare a newly measured impedance value for the electrical path to the threshold value; and

indicate a possible condition of the electrical path based on the comparison.

34. The system of claim 33, further comprising a user interface module configured to display an alarm that indicates the possible condition of the electrical path.

35. The system of claim 33, wherein the one or more processors are configured to determine the impedance value at least by measuring the plurality of measured impedance values for the electrical path at defined points in time during a time interval and determining the impedance value based on at least one of the plurality of measured impedance values measured during the time interval.

36. The system of claim 33, wherein the one or more processors are further configured to:

determine a second impedance value for a second electrical path based on a second plurality of measured impedance values for the second electrical path, wherein the second electrical path comprises a plurality of electrodes for at least one of patient stimulation or sensing;

determine a second impedance variability value based on at least one of the second plurality of measured impedance values;

determine a second threshold value based on the second determined impedance value and the second impedance variability value;

compare a newly measured impedance value for the second electrical path to the second threshold value; and

indicate a possible condition of the second electrical path based on the comparison to the second threshold value.

37. The system of claim 33, wherein the one or more processors are further configured to:

determine multiple impedance values based on a plurality of initially measured impedance values for the electrical path over a defined time period to obtain an adapted value of the determined impedance value; and

determine multiple impedance variability values based on differences between the plurality of initially measured impedance values and the multiple determined impedance values over the defined time period to obtain an adapted value of the impedance variability value.

38. The system of claim 33, wherein the one or more processors are configured to generate an indication to a user of the possible condition.

39. The system of claim 33, wherein:

the one or more processors are configured to determine the impedance value at least by determining a mean maximum impedance value based on a plurality of measured maximum impedance values;

the one or more processors are configured to determine the impedance variability value at least by determining a maximum impedance variability value based on a difference between at least one of the plurality of measured maximum impedance values and the mean maximum impedance value at a particular point in time;

the one or more processors are configured to determine the threshold value at least by determining a maximum threshold value based on the mean maximum impedance value and the maximum impedance variability value; and

the one or more processors are configured to compare the newly measured impedance value at least by comparing a newly measured maximum impedance value to the maximum threshold value.

40. The system of claim 39, wherein the one or more processors are configured to compare the newly measured maximum impedance value to the maximum threshold value at least by determining whether the newly measured maximum impedance value exceeds the maximum threshold value.

45. The system of claim 33, wherein the one or more processors are further configured to constrain the impedance variability value based on the determined impedance value.

46. The system of claim 33, wherein the one or more processors are further configured to:

determine an impedance range value for the lead based on a plurality of difference ranges between maximum and minimum impedance values;

determine an impedance range variability value based on differences between the determined impedance range value and at least one of the plurality of difference ranges;

determine a threshold range value based on the determined impedance range value and the impedance range variability value; and

compare newly measured maximum and minimum impedance values for the electrical path to the threshold range value,

wherein the one or more processors are further configured to indicate the possible condition of the electrical path based on the comparison of the newly measured maximum and minimum impedance values to the threshold range value.

48. The system of claim 33, wherein the one or more processors are configured to determine the impedance variability value at least by determining the impedance variability value based on a difference between the at least one of the plurality of measured impedance values and the determined impedance value at a particular point in time.

41. The system of 33, wherein the one or more processors are further configured to:

determine an updated impedance variability value based on the impedance variability value and a difference between the determined impedance value and the newly measured impedance value when the newly measured impedance value is below the threshold value, such that impedance variability values may adapt over time; and

determine an updated impedance value based on the determined impedance value and the newly measured impedance value when the newly measured impedance value is below the threshold value, such that determined impedance values may adapt over time.

42. The system of claim 41, wherein the one or more processors are further configured to:

repeat, over multiple time periods, the determining of the impedance value, the determining of the impedance variability value, the determining of the threshold value, the comparing of the newly measured impedance value to the threshold value, the determining of the updated impedance variability value, and the determining of the updated impedance value.

43. The system of claim 42, wherein the one or more processors are configured to indicate the possible condition when multiple newly measured impedance values have crossed the threshold value during the multiple time periods.

44. The system of claim 42, wherein when the multiple newly measured impedance values have crossed the threshold value a defined number of times, the one or more processors are further configured to determine multiple impedance variability values based on differences between a plurality of subsequently measured impedance values and the determined impedance value over a defined time period to obtain a re-adapted value of the impedance variability value.

47. The system of 46, wherein the one or more processors are further configured to:

determine an updated impedance range variability value based on the impedance range variability value and a difference between the determined impedance range value and the newly measured maximum and minimum impedance values, such that impedance range variability values may adapt over time; and

determine an updated impedance range value based on the determined impedance range value and the newly measured maximum and minimum impedance values, such that determined impedance range values may adapt over time.

49. A system comprising:

an impedance measurement module configured to receive impedance measurement values for an electrical path associated with at least one medical lead wherein the electrical path comprises a plurality of electrodes for at least one of patient stimulation or sensing;

a threshold update module configured to determine an impedance value for the electrical path based on a plurality of measured impedance values for the electrical path, to determine an impedance variability value based on at least one of the plurality of measured impedance values, and to determine a threshold value based on the determined impedance value and the impedance variability value;

a threshold comparison module configured to compare a newly measured impedance value for the electrical path to the threshold value; and

an integrity indication module configured to indicate a possible condition of the electrical path based on the comparison.

50. A computer-readable medium comprising instructions for causing one or more processors to:

determine an impedance value for an electrical path based on a plurality of measured impedance values for the electrical path, wherein the electrical path comprises a plurality of electrodes for at least one of stimulation or sensing;

determine an impedance variability value based on at least one of the plurality of measured impedance values;

determine a threshold value based on the determined impedance value and the impedance variability value;

compare a newly measured impedance value for the electrical path to the threshold value; and

indicate a possible condition of the electrical path based on the comparison.

51. A system comprising:

means for determining an impedance value for an electrical path based on a plurality of measured impedance values for the electrical path;

means for determining an impedance variability value based on at least one of the plurality of measured impedance values;

means for determining a threshold value based on the determined impedance value and the impedance variability value;

means for comparing a newly measured impedance value for the electrical path to the threshold value; and

means for indicating a possible condition of the electrical path based on the comparison.