METHODS AND IMPLANTABLE MEDICAL SYSTEMS THAT IMPLEMENT EXPOSURE MODES OF THERAPY THAT ALLOW FOR CONTINUED OPERATION DURING EXPOSURE TO A MAGNETIC DISTURBANCE

• US 20170296835A1
• Filed: 04/14/2017
• Published: 10/19/2017
• Est. Priority Date: 04/15/2016
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Yoon, Hyun J., Demmer, Wade M., Hoffman, Matthew J., Betzold, Robert A., Edmonson, Jonathan D., Ellingson, Michael L., Erickson, Mark K., Herberg, Ben E., Pronovici, Juliana E., Reinke, James D., Sheldon, Todd J., Solheim, Paul R.
• Granted Patent: US 10,441,798 B2
• Time in Patent Office: Days
• CPC Class Codes: A61N 1/3684 for stimulating the heart at multiple sites of the ventricle or the atrium
• CPC Class Codes: A61N 1/3688 configured for switching the pacing mode, e.g. from AAI to DDD
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

Implantable medical systems enter an exposure mode of operation, either manually via a down linked programming instruction or by automatic detection by the implantable system of exposure to a magnetic disturbance. A controller then determines the appropriate exposure mode by considering various pieces of information including the device type including whether the device has defibrillation capability, pre-exposure mode of therapy including which chambers have been paced, and pre-exposure cardiac activity that is either intrinsic or paced rates. Additional considerations may include determining whether a sensed rate during the exposure mode is physiologic or artificially produced by the magnetic disturbance. When the sensed rate is physiologic, then the controller uses the sensed rate to trigger pacing and otherwise uses asynchronous pacing at a fixed rate.

Claims

1. A method of controlling an exposure mode of therapy of an implantable medical device, comprising:

determining a device type of the implantable medical device;

upon detecting a need to switch to the exposure mode, selecting the exposure mode of therapy of the implantable medical device based on the device type and a pre-exposure mode of therapy; and

implementing the exposure mode of therapy at the implantable medical device by performing a first sensing of a heart rate and when the first sensing of heart rate indicates at least a first amount of noise is present, implementing an asynchronous pacing mode and then making adjustments to at least one sensing setting prior to a next sensing of the heart rate and when the first sensing of heart rate indicates that at least the first amount of noise is not present, then implementing a triggered pacing mode.

2. The method of claim 1, further comprising:

incrementing a revision counter upon making adjustments to the at least one sensing setting; and

subsequent to the next sensing of the heart rate, determining whether the revision counter exceeds a revision counter threshold such that when the revision counter does not exceed the revision counter threshold then making further adjustments to the at least one sensing setting and when the revision counter does exceed the revision counter threshold then not making further adjustments to the at least one sensing setting.

3. The method of claim 1, wherein determining the type of implantable medical device comprises determining whether the implantable medical device is a type capable of providing a defibrillation therapy and when the implantable medical device is not a type capable of providing defibrillation therapy, then selecting the exposure mode based on device type and the pre-exposure mode comprises implementing a pacing mode that paces a same set of chambers of the heart as the pre-exposure mode.

4. The method of claim 2, wherein when it is determined that the implantable medical device is capable of providing defibrillation therapy, then selecting the exposure mode based on device type and the pre-exposure mode comprises determining whether a pacing percentage of the device during a period of time prior to implementing the exposure mode exceeds a pacing percentage threshold and when the pacing percentage threshold is not exceeded then selecting a non-pacing mode as the exposure mode.

5. The method of claim 4, wherein when the pacing percentage threshold is exceeded by the pacing percentage, then determining whether the pre-exposure mode of the implantable medical device provides cardiac resynchronization therapy by pacing only a left ventricle of the heart and when the pre-exposure mode does only pace the left ventricle, then selecting the exposure mode based on device type and the pre-exposure mode comprises selecting a non-pacing mode as the exposure mode.

6. The method of claim 4, wherein when the pacing percentage threshold is exceeded by the pacing percentage, then selecting the exposure mode based on device type and the pre-exposure mode comprises implementing a pacing mode that paces a same set of chambers of the heart as the pre-exposure mode.

7. The method of claim 2, wherein when it is determined that the implantable medical device is capable of providing defibrillation therapy, then determining whether the pre-exposure mode of the implantable medical device provides cardiac resynchronization therapy by pacing only a left ventricle of the heart and when the pre-exposure mode does only pace the left ventricle, then selecting the exposure mode based on device type and the pre-exposure mode comprises selecting a non-pacing mode as the exposure mode.

8. The method of claim 7, wherein when it is determined that the pre-exposure mode does not provide cardiac resynchronization therapy by only pacing the left ventricle, then selecting the exposure mode based on device type and the pre-exposure mode comprises implementing a pacing mode that paces a same set of chambers of the heart as the pre-exposure mode.

9. The method of claim 1, wherein prior to implementing the exposure mode of therapy there are pre-exposure rates of cardiac activity and wherein the exposure mode of therapy includes providing pacing from the implantable medical device, the method further comprising:

upon detecting a need to switch to the exposure mode, selecting an exposure mode asynchronous pacing rate based on the pre-exposure rates where the exposure mode asynchronous pacing rate is used when in the asynchronous pacing mode; and

implementing the exposure mode asynchronous pacing rate at the implantable medical device while implementing the exposure mode of therapy when the asynchronous pacing mode is being implemented.

10. The method of claim 9, wherein selecting the exposure mode pacing rate based on the pre-exposure rates comprises determining whether an average rate of cardiac activity occurring during a period prior to implementing the exposure mode exceeds a rate threshold, when the average rate does not exceed the threshold then pacing at a pre-defined fixed rate as the exposure mode pacing rate and when the average does exceed the threshold then pacing at a rate equal to the average rate plus a fixed adjustment up to a pre-defined upper limit.

11. The method of claim 10, wherein the pre-exposure rates of cardiac activity are intrinsic rates.

12. The method of claim 11, wherein the pre-exposure rates of cardiac activity are paced rates.

13. A method of controlling an exposure mode of therapy of an implantable medical device, comprising:

determining a type of an implantable medical device by determining whether the implantable medical device is capable of providing a therapy to multiple chambers of a heart;

when the implantable medical device is not a type capable of providing therapy to multiple chambers of the heart, then determining whether the device is of a type capable of defibrillation therapy;

when the device is not capable of defibrillation therapy then comparing a pacing percentage of the device to a first threshold;

when the device is capable of defibrillation therapy then comparing a pacing percentage of the device to a second threshold; and

selecting the exposure mode based on device type and the pre-exposure mode by implementing a pacing mode that paces a same chamber of the heart as the pre-exposure mode when the pacing percentage exceeds the first threshold when the device is not capable of defibrillation therapy or the second threshold when the device is capable of defibrillation therapy.

14. The method of claim 13, wherein implementing the pacing mode that paces the same chamber of the heart as the pre-exposure mode comprises pacing asynchronously.

15. The method of claim 14, wherein a rate for pacing asynchronously is determined by comparing an average rate of cardiac activity over a period of time preceding the exposure mode to a rate threshold and when the rate threshold is not exceeded then pacing at a pre-defined fixed rate.

16. The method of claim 15, wherein when the rate threshold is exceeded then pacing at a rate equal to the average rate of cardiac activity plus a fixed adjustment with the rate having an upper limit.

17. The method of claim 14, wherein a rate for pacing asynchronously is determined by comparing a rate for a pre-defined percentile of a statistical distribution of rates of cardiac activity to a rate threshold and when the rate threshold is not exceeded then pacing at a pre-defined fixed rate.

18. The method of claim 17, wherein when the rate threshold is exceeded then pacing at a rate equal to the rate for the pre-defined percentile of the statistical distribution of rates plus a fixed adjustment with the rate having an upper limit.

19. The method of claim 13, wherein when the pacing percentage does not exceed the first threshold when the device is not capable of defibrillation therapy or does not exceed the second threshold when the device is capable of defibrillation therapy, then selecting the exposure mode based on device type and the pre-exposure mode comprises selecting a non-pacing mode as the exposure mode.

20. The method of claim 13, wherein when the implantable medical device is a type capable of providing therapy to multiple chambers of the heart, then comparing a pacing percentage of the device to a third threshold, and selecting the exposure mode based on device type and the pre-exposure mode comprises implementing a pacing mode that paces a same set of chambers of the heart as the pre-exposure mode when the pacing percentage exceeds the third threshold.

21. The method of claim 20, wherein implementing the pacing mode that paces the same set of chambers of a heart as the pre-exposure mode comprises pacing asynchronously.

22. The method of claim 20, wherein when the pacing percentage does not exceed the third threshold, then selecting the exposure mode based on device type and the pre-exposure mode comprises selecting a non-pacing mode as the exposure mode.

23. The method of claim 13, wherein implementing the pacing mode that paces the same chamber of the heart as the pre-exposure mode comprises determining an asynchronous rate based on whether prior cardiac activity exceeds a rate threshold such that a first rate is selected as the asynchronous rate when the prior cardiac activity does not exceed the rate threshold and a second rate is selected as the asynchronous rate when the prior cardiac activity does exceed the threshold.

24. The method of claim 23, further comprising continuously sensing an intrinsic rate and determining whether the intrinsic rate is artificial or physiologic by comparing the intrinsic rate to a physiologic range, when the intrinsic rate is physiologic then pacing during the exposure mode at a triggered pacing rate based on the intrinsic rate and when the intrinsic rate is artificial then pacing during the exposure mode at the asynchronous rate.

25. The method of claim 23, wherein when the device is capable of providing therapy to both the atrial and ventricular chambers, then the method further comprises continuously sensing an atrial intrinsic rate and a ventricular intrinsic rate, determining whether the atrial intrinsic rate and the ventricular intrinsic rate are artificial or physiologic by comparing the atrial and ventricular intrinsic rates to a physiologic range, when both the atrial and ventricular intrinsic rates are physiologic then atrial pacing at an atrial triggered pacing rate based on the atrial intrinsic rate and ventricular pacing at a ventricular triggered pacing rate based on the ventricular intrinsic rate during the exposure mode, when at least the ventricular intrinsic rate is artificial then pacing during the exposure mode at the asynchronous rate, and when the atrial intrinsic rate is artificial and the ventricular intrinsic rate is physiologic, then ventricular pacing at a ventricular triggered pacing rate based on the ventricular intrinsic rate during the exposure mode.

26. The method of claim 13, further comprising continuously sensing an intrinsic rate and determining whether the intrinsic rate is artificial or physiologic by comparing the intrinsic rate to a physiologic range, when the intrinsic rate is physiologic then pacing during the exposure mode at a triggered pacing rate based on the intrinsic rate and when the intrinsic rate is artificial then pacing during the exposure mode at an asynchronous rate.

27. The method of claim 13, wherein when the device is capable of providing therapy to both the atrial and ventricular chambers, then the method further comprises continuously sensing an atrial intrinsic rate and a ventricular intrinsic rate, determining whether the atrial intrinsic rate and the ventricular intrinsic rate are artificial or physiologic by comparing the atrial and ventricular intrinsic rates to a physiologic range, when both the atrial and ventricular intrinsic rates are physiologic then atrial pacing at an atrial triggered pacing rate based on the atrial intrinsic rate and ventricular pacing at a ventricular triggered pacing rate based on the ventricular intrinsic rate during the exposure mode, when at least the ventricular intrinsic rate is artificial then pacing during the exposure mode at the asynchronous rate, and when the atrial intrinsic rate is artificial and the ventricular intrinsic rate is physiologic, then ventricular pacing at a ventricular triggered pacing rate based on the ventricular intrinsic rate during the exposure mode.

28. An implantable medical system comprising:

a device for providing electrical sensing and pacing; and

a controller that is in control of the device to provide an exposure mode of therapy by the device and that is configured to determine a device type, detect a need to switch to the exposure mode, select the exposure mode of therapy of the device based on the device type and a pre-exposure mode of therapy, and implement the exposure mode of therapy at the device by performing a first sensing of a heart rate and when the first sensing of heart rate indicates at least a first amount of noise is present, implementing an asynchronous pacing mode and then making adjustments to at least one sensing setting prior to a next sensing of the heart rate and when the first sensing of heart rate indicates that at least the first amount of noise is not present, then implementing a triggered pacing mode.

29. An implantable medical system comprising:

a device for providing electrical sensing and pacing; and

a controller that is in control of the device to provide an exposure mode of therapy by the device and is configured to determine a type of the device by determining whether the device is a type capable of providing a therapy to multiple chambers of a heart and when the device is not a type capable of providing therapy to multiple chambers of the heart, then determining whether the device is of a type capable of defibrillation therapy, and when the device is not capable of defibrillation therapy then comparing a pacing percentage of the device to a first threshold, and when the device is capable of defibrillation therapy then comparing a pacing percentage of the device to a second threshold, and selecting the exposure mode based on device type and the pre-exposure mode comprises implementing a pacing mode that paces a same chamber of the heart as the pre-exposure mode when the pacing percentage exceeds the first threshold when the device is not capable of defibrillation therapy or the second threshold when the device is capable of defibrillation therapy.

30. A method for controlling an exposure mode of therapy of an implantable medical device, comprising:

determining whether the device is a defibrillator type and if so, then determining whether a lower pacing rate is lower than a rate threshold and whether a ventricular pacing percentage is lower than a pacing percentage threshold;

when the lower pacing rate is lower than the rate threshold and the pacing percentage is lower than the pacing percentage threshold, then choosing a non-pacing mode as the exposure mode of therapy; and

when the lower rate is not lower than the rate threshold and/or the pacing percentage is not lower than the pacing percentage, then choosing a permanent pacing mode of the device as the exposure mode of therapy.

31. A method for controlling an exposure mode of therapy of an implantable medical device, comprising:

determining whether a heart rate exceeds a first threshold;

when the heart rate does not exceed the first threshold, then setting a pacing rate for the exposure mode to the heart rate plus a first adjustment;

when the heart rate does exceed the first threshold, then determining whether the heart rate exceeds a second threshold that is higher than the first threshold and whether a ventricular pacing percentage exceeds a pacing percentage threshold;

when the heart rate does not exceed the second threshold and/or the ventricular pacing percentage does not exceed the pacing percentage threshold, then setting the pacing rate for the exposure mode to the heart rate plus a second adjustment but limited to a specified maximum;

when the heart rate does exceed the second threshold, the ventricular pacing percentage does exceed the pacing percentage threshold, and a device type is other than a resynchronization therapy device, then setting the pacing rate to a fixed amount higher than the first threshold and lower than the second threshold and setting a pacing mode to a VOO mode; and

when the heart rate does exceed the second threshold, the ventricular pacing percentage does exceed the pacing percentage threshold, and the device type is a resynchronization therapy device, then setting the pacing rate to the heart rate plus the second adjustment but limited to the specified maximum.