INTERDEVICE IMPEDANCE

• US 20100114204A1
• Filed: 01/30/2009
• Published: 05/06/2010
• Est. Priority Date: 10/31/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Krause, Paul G., Burnes, John E.
• Granted Patent: US 9,289,613 B2
• Time in Patent Office: Days
• US Class Current: 607/4
• CPC Class Codes: A61N 1/36114 Cardiac control, e.g. by vagal stimulation stimulating the heart A61N1/362
• CPC Class Codes: A61N 1/36146 specified by the stimulation parameters
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/37288 Communication to several implantable medical devices within one patient
• CPC Class Codes: A61N 2001/083 Monitoring integrity of contacts, e.g. by impedance measurement

Abstract

An electrical parameter value indicative of an impedance of an electrical path between a first medical device implanted within a patient and a second medical device implanted within the patient may be determined by generating and delivering an electrical signal between electrodes connected to the first medical device and sensing the electrical signal with two or more sense electrodes connected to the second medical device. In some examples, the electrical parameter value indicative of the impedance may be used to detect a system integrity issue, such as relative movement between the first and second medical devices, such as between leads connected to the medical devices, or a lead-related condition. In other examples, the determined impedance may indicate a transthoracic impedance of the patient.

Claims

1. A method comprising:

delivering an electrical signal between a first electrode and a second electrode connected to a first implantable medical device;

sensing the electrical signal with a second implantable medical device; and

determining an electrical parameter value indicative of an impedance of a path between the first and second implantable medical devices based on the sensed electrical signal.

2. The method of claim 1, the first implantable medical device being configured to deliver at least one of pacing, cardioversion or defibrillation therapy to a heart of a patient and the second implantable medical device being configured to deliver electrical stimulation to a tissue site within the patient.

3. The method of claim 2, wherein the tissue site comprises at least one of a nonmyocardial tissue site or a nonvascular cardiac tissue site.

4. The method of claim 1, the first implantable medical device being configured to deliver electrical stimulation to a tissue site within a patient and the second implantable medical device being configured to deliver at least one of pacing, cardioversion or defibrillation therapy to a heart of the patient.

5. The method of claim 1, further comprising determining whether electrodes connected to the first implantable medical device have moved relative to electrodes connected to the second implantable medical device based on the electrical parameter value.

6. The method of claim 5, wherein determining whether electrodes connected to the first implantable medical device have moved relative to electrodes connected to the second implantable medical device comprises comparing the electrical parameter value to a threshold value.

7. The method of claim 1, further comprising determining a presence of a lead-related condition based on the electrical parameter value.

8. The method of claim 1, further comprising determining whether the electrical parameter value is within a predetermined range of values, and generating an indication if the electrical parameter value is not within the predetermined range of values.

9. The method of claim 8, further comprising:

determining a patient posture or a patient activity level; and

selecting the predetermined range of values based on the patient posture or a patient activity level.

10. The method of claim 1, further comprising determining a rate of change of the electrical parameter value over time and generating an indication if the rate of change exceeds a threshold value.

11. The method of claim 1, wherein the impedance comprises the impedance of an electrical path between at least one of the first electrode or the second electrode connected to the first implantable medical device and a third and a fourth electrode connected to the second implantable medical device.

12. The method of claim 1, wherein the electrical signal comprises a signal characteristic less than a tissue activation threshold of a patient in which the first and second implantable medical devices are implanted.

13. The method of claim 1, further comprising controlling at least one of the first or second implantable medical devices to deliver therapy to a patient based on the electrical parameter value indicative of the impedance of the path between the first and second implantable medical devices.

14. The method of claim 1, further comprising modifying therapy delivery by the first or second medical devices based on the electrical parameter value.

15. The method of claim 14, wherein modifying therapy delivery by the first or second medical devices based on the electrical parameter value comprises suspending therapy delivery by the first or second medical devices based on the electrical parameter value.

16. The method of claim 1, further comprising generating an indication to a user based on the electrical parameter value.

17. The method of claim 16, wherein generating the indication comprises generating the indication with at least one of the implantable medical device or an external device.

18. The method of claim 1, wherein the electrical signal comprises a first electrical signal and the electrical parameter value comprises a first electrical parameter value, and wherein the first and second electrodes define a first electrode combination, the method further comprising:

delivering a second electrical signal between electrodes of a second electrode combination connected to the first implantable medical device, wherein the second electrode combination comprises at least one different electrode than the first electrode combination;

sensing the second electrical signal with the second implantable medical device;

determining a second electrical parameter value indicative of the impedance of the path between the first and second implantable medical devices based on the sensed second electrical signal; and

detecting movement of the first and second implantable medical devices relative to each other or movement of leads connected to the first and second implantable medical devices relative to each other based on the first and second electrical parameter values.

19. The method of claim 1, wherein the electrical signal comprises a first electrical signal and the electrical parameter value comprises a first electrical parameter value, and wherein sensing the first electrical signal with the second implantable medical device comprises sensing the first electrical signal via a first electrode combination including electrodes connected to the second implantable medical device, the method further comprising:

delivering a second electrical signal between the first and second electrodes connected to the first implantable medical device;

sensing the second electrical signal with a second electrode combination including electrodes connected to the second implantable medical device, wherein the second electrode combination comprises at least one different electrode than the first electrode combination;

determining a second electrical parameter value indicative of the impedance of the path between the first and second implantable medical devices based on the sensed second electrical signal; and

detecting movement of the first and second implantable medical devices relative to each other or movement of leads connected to the first and second implantable medical devices relative to each other based on the first and second electrical parameter values.

20. The method of claim 1, further comprising storing at least one of the electrical parameter value or a trend in the electrical parameter value over time in a memory.

21. The method of claim 1, further comprising determining a trend in the electrical parameter value over time.

22. The method of claim 21, further comprising transmitting data indicative of the trend in the electrical parameter value over time to a user.

23. A method comprising:

sensing an electrical signal with electrodes connected to a first implantable medical device, the electrical signal being generated by a second implantable medical device different than the first implantable medical device; and

determining an electrical parameter value indicative of an impedance of a path between the first and second implantable medical devices based on the sensed electrical signal.

24. The method of claim 23, further comprising determining whether the electrical parameter value is within a predetermined range of values, and generating an indication if the electrical parameter value is not within the predetermined range of values.

25. The method of claim 24, wherein generating the indication comprises generating the indication with at least one of the implantable medical device or an external device.

26. The method of claim 23, further comprising determining a rate of change of the electrical parameter value over time and generating an indication if the rate of change exceeds a threshold value.

27. The method of claim 23, further comprising receiving an indication of at least one of a voltage or a current of the electrical signal generated by the second implantable medical device.

28. A system comprising:

a first implantable medical device connected to a first electrode and a second electrode, wherein the first implantable medical device delivers an electrical signal between the first and second electrodes;

a second implantable medical device that senses the electrical signal; and

a processor that determines an electrical parameter value indicative of an impedance of a path between the first and second implantable medical devices based on the sensed electrical signal.

29. The system of claim 28, the first implantable medical device being configured to deliver at least one of pacing, cardioversion or defibrillation therapy to a heart of a patient and the second implantable medical device being configured to deliver electrical stimulation to a tissue site within the patient.

30. The system of claim 29, wherein the tissue site comprises at least one of a nonmyocardial tissue site or a nonvascular cardiac tissue site.

31. The system of claim 28, the first implantable medical device being configured to deliver electrical stimulation to a tissue site within a patient and the second implantable medical device being configured to deliver at least one of pacing, cardioversion or defibrillation therapy to a heart of the patient.

32. The system of claim 28, wherein the processor determines whether electrodes connected to the first implantable medical device have moved relative to electrodes connected to the second implantable medical device based on the electrical parameter value.

33. The system of claim 28, wherein the processor determines a presence of a lead-related condition based on the electrical parameter value.

34. The system of claim 28, wherein the processor determines whether the electrical parameter value is within a predetermined range of values, and generates an indication if the electrical parameter value is not within the predetermined range of values.

35. The system of claim 34, wherein the processor generates the indication via at least one of the implantable medical device or an external device.

36. The system of claim 34, further comprising:

a memory that stores a plurality of ranges of values and associated patient activity levels or posture levels; and

a sensor that generates a sensor signal indicative of patient activity level or posture, wherein the processor determines the patient activity level or posture based on the sensor signal and selects the predetermined range of values from the memory based on the determined patient activity level or posture.

37. The system of claim 28, wherein the processor determines a rate of change of the electrical parameter value over time and generates an indication if the rate of change exceeds a threshold value.

38. The system of claim 28, wherein the impedance comprises a transthoracic impedance of a patient in which the first and second implantable medical devices are implanted.

39. The system of claim 28, wherein the electrical signal comprises a signal characteristic that is less than a tissue activation threshold of a patient in which the first and second implantable medical devices are implanted.

40. The system of claim 28, wherein the first medical device comprises the processor.

41. The system of claim 28, wherein the second medical device comprises the processor.

42. The system of claim 28, further comprising a medical device programmer comprising the processor.

43. The system of claim 28, wherein the processor controls at least one of the first or second implantable medical devices to deliver therapy to a patient based on the electrical parameter value.

44. The system of claim 28, wherein the processor modifies a therapy parameter of at least one of the first or second implantable medical devices based on the electrical parameter value.

45. The system of claim 28, wherein the processor stores at least one of the electrical parameter value or a trend in the electrical parameter value over time in a memory.

46. The system of claim 28, wherein the processor determines a trend in the electrical parameter value over time.

47. The system of claim 46, wherein the processor transmits data indicative of the trend in the electrical parameter value over time to a user.

48. A system comprising:

means for delivering an electrical signal between a first electrode and a second electrode of a first implantable medical device;

means for sensing the electrical signal at a second implantable medical device; and

means for determining an impedance value of a path between the first and second implantable medical devices based on the sensed electrical signal.

49. The system of claim 48, further comprising means for determining whether the first implantable medical device and the second implantable medical device have moved relative to each other, or whether electrodes connected to the first and second implantable medical devices have moved relative to each other based on the electrical parameter value.

50. The system of claim 48, further comprising means for determining whether a lead-related condition is present based on the electrical parameter value.