Therapy control based on the rate of change of intracardiac impedance

• US 20070005114A1
• Filed: 06/29/2005
• Published: 01/04/2007
• Est. Priority Date: 06/29/2005
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Pastore, Joseph, Salo, Rodney, Hartley, Jesse, Stahmann, Jeffrey
• Granted Patent: US 7,376,463 B2
• Time in Patent Office: Days
• US Class Current: 607/17
• CPC Class Codes: A61N 1/30 Apparatus for iontophoresis, i.e. transfer of media in ionic state by an electromotoric force into the body, or cataphoresis
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

A system comprising a medical device that includes an impedance measurement circuit adapted to be coupled to implantable electrodes to obtain an intracardiac impedance signal between electrodes, a therapy circuit operable to deliver a therapy to a subject, and a controller circuit coupled to the impedance measurement circuit and the therapy circuit. The controller circuit determines a time rate of change of the intracardiac impedance signal and adjusts at least one parameter related to therapy in a manner that alters the rate of change.

Claims

1. A system comprising a medical device including:

a medical device including;

an impedance measurement circuit adapted to be coupled to implantable electrodes to obtain an intracardiac impedance signal between electrodes;

a therapy circuit operable to deliver a therapy to a subject; and

a controller circuit coupled to the impedance measurement circuit and the therapy circuit, wherein the controller circuit is operable to determine a time rate of change of the intracardiac impedance signal, and to adjust at least one parameter related to therapy in manner that alters the rate of change.

2. The system of claim 1, wherein the controller circuit is further operable to adjust the parameter in a closed feedback loop manner.

3. The system of claim 1, wherein the controller circuit is further operable to adjust the parameter to alter a peak value of the rate of change.

4. The system of claim 1, wherein the controller circuit adjusts at least one therapy parameter to maximize a measured peak absolute value of the intracardiac impedance time rate of change.

5. The system of claim 4, wherein the measured peak absolute value is a measured peak magnitude of a decreasing intracardiac impedance.

6. The system of claim 1, further including a plurality of implantable electrodes adaptable to sense electrical signals of a heart of a subject.

7. The system of claim 6, wherein the implantable electrodes include electrodes adapted for placement in one of a coronary sinus and a right ventricle, and wherein the impedance circuit obtains an intracardiac impedance signal from the left ventricle.

8. The system of claim 6, wherein the electrodes are adapted for placement in one of a right atrium and a right ventricle, and wherein the impedance circuit obtains an intracardiac impedance signal from the right ventricle.

9. The system of claim 6, wherein the electrodes are adapted for placement in a right ventricle and on a left ventricle lateral wall, and wherein the impedance circuit obtains an intracardiac impedance signal from between the right ventricle and the left ventricle lateral wall.

10. The system of claim 6, wherein the electrodes include at least a first set of electrodes adapted for placement to correspond to a first impedance vector and a second set of electrodes adapted for placement to correspond to a different second impedance vector, and wherein the impedance circuit is operable to obtain a first intracardiac impedance signal from the first set of electrodes and a second intracardiac impedance signal from the second set of electrodes, and wherein the controller circuit is operable to determine peak values of time rates of change of the first and second intracardiac impedance signals and to adjust at least one therapy parameter in a closed loop feedback arrangement to adjust a difference in time between the first intracardiac impedance signal reaching a peak rate of change value and the second intracardiac impedance signal reaching a peak rate of change value.

11. The system of claim 8, wherein the first impedance vector provides an intracardiac impedance signal associated with a right ventricle and the second impedance vector provides an intracardiac impedance signal associated with a left ventricle.

12. The system of claim 1, wherein the medical device is an implantable medical device and provides cardiac function management therapy.

13. The system of claim 12, wherein the medical device further includes a memory circuit coupled to the controller circuit, the controller circuit operable to store trend data related to a rate of change of an intracardiac impedance signal.

14. The system of claim 13, further including a second device to communicate wirelessly with the medical device, and wherein the medical device is operable to communicate the trend data to the second device.

15. The system of claim 14, wherein the second device is operable to communicate with a communication network.

16. A method comprising:

sensing at least one intracardiac impedance signal of a patient using a medical device;

measuring a rate of change of the intracardiac impedance signal with respect to time; and

adjusting at least one therapy parameter provided to the patient in a manner that alters the rate of change.

17. The method of claim 16, wherein adjusting the therapy parameter includes adjusting the parameter in a closed loop feedback manner.

18. The method of claim 16, wherein adjusting the therapy parameter to alter the rate of change includes adjusting the therapy parameter to increase the rate of change.

19. The method of claim 16, wherein adjusting at least one therapy parameter includes adjusting one or more parameters to maximize a peak absolute value of the rate of change.

20. The method of claim 16, wherein adjusting at least one therapy parameter includes adjusting one or more parameters to maximize a peak magnitude of a negative rate of change.

21. The method of claim 16, wherein adjusting at least one therapy parameter includes adjusting one or more parameters to increase a peak magnitude of both a positive rate of change value and a peak magnitude of a negative rate of change.

22. The method of claim 16, wherein measuring a rate of change of intracardiac impedance signal includes measuring a rate of change of an intracardiac impedance signal associated with a right ventricle.

23. The method of claim 16, wherein measuring a rate of change of intracardiac impedance includes measuring a rate of change of an intracardiac impedance signal associated with a left ventricle.

24. The method of claim 16, wherein measuring a rate of change of intracardiac impedance includes measuring a rate of change of an intracardiac impedance signal sensed between a right ventricle and a left ventricle.

25. The method of claim 16, wherein sensing at least one intracardiac impedance signal includes sensing first and second intracardiac impedance signals along different first and second impedance vectors, wherein measuring a rate of change of an intracardiac impedance signal includes measuring rates of change of the first and second intracardiac impedance signals, and wherein adjusting at least one therapy parameter includes adjusting a time difference between the first intracardiac impedance signal reaching a peak rate of change value and the second intracardiac impedance signal reaching a peak rate of change value.

26. The method of claim 25, wherein the first intracardiac impedance signal is sensed from a right ventricle and the second intracardiac impedance signal is sensed from a left ventricle.

27. The method of claim 25, wherein adjusting at least one therapy parameter includes adjusting a resynchronization pacing therapy parameter.

28. The method of claim 25, wherein adjusting at least one therapy parameter includes adjusting at least one pacing site.

29. The method of claim 16, wherein the method further includes communicating trend data related to a time rate of change of intracardiac impedance from the medical device.

30. The method of claim 16, wherein measuring a rate of change of the intracardiac impedance signal with respect to time further includes:

monitoring peak values of measured rates of change;

detecting a sudden change in a peak rate of change value and a sudden increase in heart rate; and

using the increase in heart rate and the sudden change in peak rate of change value as an indication of tachyarrhyrhmia, and wherein adjusting at least one therapy parameter in accordance with the measured time rate of change includes adjusting at least one therapy parameter related to treatment of tachyarrhythmia.

31. The method of claim 30, wherein detecting a sudden change in a peak rate of change value includes defining a sudden change as a percentage change in the peak rate of change value over a predetermined number of cardiac cycles.

32. A system comprising:

means for sensing at least one intracardiac impedance signal of a patient using a medical device;

means for measuring a rate of change of the intracardiac impedance signal with respect to time; and

means for adjusting at least one therapy parameter provided to the patient in a closed-loop feedback manner that tends to increase the rate of change.

33. The system of claim 32, wherein means for adjusting at least one therapy parameter includes means for adjusting one or more parameters to maximize a peak absolute value of the rate of change.

34. The system of claim 32, wherein means for adjusting at least one therapy parameter includes means for adjusting one or more parameters to maximize a peak magnitude of a negative rate of change.

35. The system of claim 32, wherein means for adjusting at least one therapy parameter includes means for adjusting one or more parameters to increase a peak magnitude of both a positive rate of change value and a peak magnitude of a negative rate of change.