Use of thoracic and extra-thoracic impedance for diagnostic monitoring

• US 8,868,185 B2
• Filed: 11/27/2012
• Issued: 10/21/2014
• Est. Priority Date: 10/31/2011
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Zielinski, Todd M., Hettrick, Douglas A., Cho, Yong K., Warman, Eduardo N., Sobotka, Paul A.
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): CAREY, MICHAEL JAMES
• Application Number:
  US13/686,359
• Publication Number:
  US 20140148867A1
• Time in Patent Office: 693 Days
• Field of Search: 607/17, 607/7
• US Class Current: 607/17
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/085 Measuring impedance of respiratory organs or lung elasticity
• CPC Class Codes: A61M 27/00 Drainage appliance for wounds or the like , i.e. wound drains, implanted drains negative pressure wound therapy devices A61M1/90; implements for holding wound open A61B17/02 ; middle ear drainage A61F11/202
• CPC Class Codes: A61N 1/3627 for treating a mechanical deficiency of the heart, e.g. congestive heart failure or cardiomyopathy
• CPC Class Codes: A61N 1/36507 controlled by gradient or slope of the heart potential
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

A medical device and associated method for delivery of a cardiac therapy that includes determining a first impedance signal along a thoracic electrode vector extending within a portion of a thoracic cavity, determining a second impedance signal along an extra-thoracic electrode vector extending outside the thoracic cavity, comparing first amplitude measurements corresponding to the first impedance signals and second amplitude measurements corresponding to the second impedance signals, comparing first slope measurements corresponding to the first impedance signals and second slope measurements corresponding to the second impedance signals, and determining delivery of the cardiac therapy in response to the comparing.

Claims

1. A medical device for delivering a cardiac therapy, comprising:

a plurality of electrodes to sense a first impedance signal along a thoracic electrode vector extending within a portion of a thoracic cavity and a second impedance signal along an extra-thoracic electrode vector extending outside the thoracic cavity;

a therapy delivery module to deliver the therapy via electrodes of the plurality of electrodes; and

a processor configured to compare first amplitude measurements corresponding to the first impedance signals and second amplitude measurements corresponding to the second impedance signals, compare first slope measurements corresponding to the first impedance signals and second slope measurements corresponding to the second impedance signals, and control the therapy delivery module to deliver the cardiac therapy in response to the comparing, wherein the processor is further configured to determine amplitude differences between the first amplitude measurements and the second amplitude measurements at a predetermined amplitude difference interval, determine whether the amplitude differences correspond to decreasing impedance along the thoracic electrode vector relative to the extra-thoracic electrode vector, and deliver a first therapy in response to decreasing impedance along the thoracic electrode vector relative to the extra-thoracic electrode vector, and wherein the processor is further configured to determine whether the amplitude differences correspond to decreasing impedance along the extra-thoracic electrode vector relative to the thoracic electrode vector, and deliver a second therapy different from the first therapy in response to decreasing impedance along the extra-thoracic electrode vector relative to the thoracic electrode vector.

2. The medical device of claim 1, wherein the first therapy corresponds to pulmonary edema and the second therapy corresponds to tissue fluid removal.

3. A medical device for delivering a cardiac therapy, comprising:

a plurality of electrodes to sense a first impedance signal along a thoracic electrode vector extending within a portion of a thoracic cavity and a second impedance signal along an extra-thoracic electrode vector extending outside the thoracic cavity;

a therapy delivery module to deliver the therapy via electrodes of the plurality of electrodes; and

a processor configured to compare first amplitude measurements corresponding to the first impedance signals and second amplitude measurements corresponding to the second impedance signals, compare first slope measurements corresponding to the first impedance signals and second slope measurements corresponding to the second impedance signals, and control the therapy delivery module to deliver the cardiac therapy in response to the comparing, wherein the processor is further configured to determine amplitude differences between the first amplitude measurements and the second amplitude measurements, determine an amplitude difference trend in response to the determined amplitude differences, determine slope differences between the first slope measurements and the second slope measurements, determine a slope difference trend in response to the determined slope differences, and determine delivery of the cardiac therapy in response to the amplitude difference trend and the slope difference trend, compare a current determined amplitude difference trend and a previously determined amplitude difference trend, determine amplitude difference trend change in response to the comparing of the current determined amplitude difference trend and a previously determined amplitude difference trend, and determine delivery of the cardiac therapy in response to the determined amplitude difference trend change, and compare a current determined slope difference trend and a previously determined slope difference trend, determine slope difference trend change in response to the comparing of the current determined slope difference trend and a previously determined slope difference trend, and determine delivery of the cardiac therapy in response to the determined slope difference trend change, wherein the processor is further configured to determine whether the amplitude difference indicates either a decreasing impedance along the thoracic electrode vector relative to the extra-thoracic electrode vector or a decreasing impedance along the extra-thoracic electrode vector relative to the thoracic electrode vector, deliver a first therapy in response to decreasing impedance along the thoracic electrode vector relative to the extra-thoracic electrode vector, and deliver a second therapy different from the first therapy in response to decreasing impedance along the extra-thoracic electrode vector relative to the thoracic electrode vector.

4. The medical device of claim 3, wherein the first therapy corresponds to pulmonary edema and the second therapy corresponds to tissue fluid removal.

5. A medical device for delivering a cardiac therapy, comprising:

a plurality of electrodes to sense a first impedance signal along a thoracic electrode vector extending within a portion of a thoracic cavity and a second impedance signal along an extra-thoracic electrode vector extending outside the thoracic cavity;

a therapy delivery module to deliver the therapy via electrodes of the plurality of electrodes; and

a processor configured to compare first amplitude measurements corresponding to the first impedance signals and second amplitude measurements corresponding to the second impedance signals, compare first slope measurements corresponding to the first impedance signals and second slope measurements corresponding to the second impedance signals, and control the therapy delivery module to deliver the cardiac therapy in response to the comparing, wherein the processor is further configured to determine amplitude differences between the first amplitude measurements and the second amplitude measurements, determine an amplitude difference trend in response to the determined amplitude differences, determine slope differences between the first slope measurements and the second slope measurements, determine a slope difference trend in response to the determined slope differences, and determine delivery of the cardiac therapy in response to the amplitude difference trend and the slope difference trend, and wherein the processor is further configured to compare a current determined amplitude difference trend and a previously determined amplitude difference trend, determine whether there is a change in amplitude difference trend in response to the comparing of the current determined amplitude difference trend and a previously determined amplitude difference trend, and deliver a first therapy in response to determining no change in amplitude difference trend.

6. The medical device of claim 5, wherein the processor is further configured to compare a current determined slope difference trend and a previously determined slope difference trend in response to determining change in amplitude difference trend, determine whether there is a change in slope difference trend in response to the comparing of the current determined slope difference trend and a previously determined slope difference trend, deliver a second therapy in response to determining no change in slope difference trend, and deliver a third therapy in response to determining change in slope difference trend.

7. A method for determining delivery of a cardiac therapy, comprising:

determining a first impedance signal along a thoracic electrode vector extending within a portion of a thoracic cavity;

determining a second impedance signal along an extra-thoracic electrode vector extending outside the thoracic cavity;

comparing first amplitude measurements corresponding to the first impedance signals and second amplitude measurements corresponding to the second impedance signals;

comparing first slope measurements corresponding to the first impedance signals and second slope measurements corresponding to the second impedance signals;

determining delivery of the cardiac therapy in response to the comparing determining amplitude differences between the first amplitude measurements and the second amplitude measurements at a predetermined amplitude difference interval;

determining whether the amplitude differences correspond to decreasing impedance along the thoracic electrode vector relative to the extra-thoracic electrode vector;

delivering a first therapy in response to decreasing impedance along the thoracic electrode vector relative to the extra-thoracic electrode vector;

determining whether the amplitude differences correspond to decreasing impedance along the extra-thoracic electrode vector relative to the thoracic electrode vector; and

delivering a second therapy different from the first therapy in response to decreasing impedance along the extra-thoracic electrode vector relative to the thoracic electrode vector.

8. The method of claim 7, wherein the first therapy corresponds to pulmonary edema and the second therapy corresponds to tissue fluid removal.

9. A method for determining delivery of a cardiac therapy, comprising:

determining a first impedance signal along a thoracic electrode vector extending within a portion of a thoracic cavity;

determining a second impedance signal along an extra-thoracic electrode vector extending outside the thoracic cavity;

comparing first amplitude measurements corresponding to the first impedance signals and second amplitude measurements corresponding to the second impedance signals;

comparing first slope measurements corresponding to the first impedance signals and second slope measurements corresponding to the second impedance signals;

determining delivery of the cardiac therapy in response to the comparing;

determining amplitude differences between the first amplitude measurements and the second amplitude measurements;

determining an amplitude difference trend in response to the determined amplitude differences;

determining slope differences between the first slope measurements and the second slope measurements;

determining a slope difference trend in response to the determined slope differences; and

determining delivery of the cardiac therapy in response to the amplitude difference trend and the slope difference trend;

comparing a current determined amplitude difference trend and a previously determined amplitude difference trend;

determining amplitude difference trend change in response to the comparing of the current determined amplitude difference trend and a previously determined amplitude difference trend;

determining delivery of the cardiac therapy in response to the determined amplitude difference trend change;

comparing a current determined slope difference trend and a previously determined slope difference trend;

determining slope difference trend change in response to the comparing of the current determined slope difference trend and a previously determined slope difference trend;

determining delivery of the cardiac therapy in response to the determined slope difference trend change;

determining whether the amplitude difference indicates either a decreasing impedance along the thoracic electrode vector relative to the extra-thoracic electrode vector or a decreasing impedance along the extra-thoracic electrode vector relative to the thoracic electrode vector;

delivering a first therapy in response to decreasing impedance along the thoracic electrode vector relative to the extra-thoracic electrode vector; and

delivering a second therapy different from the first therapy in response to decreasing impedance along the extra-thoracic electrode vector relative to the thoracic electrode vector.

10. The method of claim 9, wherein the first therapy corresponds to pulmonary edema and the second therapy corresponds to tissue fluid removal.

11. A method for determining delivery of a cardiac therapy, comprising:

determining a first impedance signal along a thoracic electrode vector extending within a portion of a thoracic cavity;

determining a second impedance signal along an extra-thoracic electrode vector extending outside the thoracic cavity;

comparing first amplitude measurements corresponding to the first impedance signals and second amplitude measurements corresponding to the second impedance signals;

comparing first slope measurements corresponding to the first impedance signals and second slope measurements corresponding to the second impedance signals;

determining delivery of the cardiac therapy in response to the comparing;

determining amplitude differences between the first amplitude measurements and the second amplitude measurements;

determining an amplitude difference trend in response to the determined amplitude differences;

determining slope differences between the first slope measurements and the second slope measurements;

determining a slope difference trend in response to the determined slope differences;

determining delivery of the cardiac therapy in response to the amplitude difference trend and the slope difference trend;

comparing a current determined amplitude difference trend and a previously determined amplitude difference trend;

determining whether there is a change in amplitude difference trend in response to the comparing of the current determined amplitude difference trend and a previously determined amplitude difference trend; and

delivering a first therapy in response to determining no change in amplitude difference trend.

12. The method of claim 11, further comprising:

comparing a current determined slope difference trend and a previously determined slope difference trend in response to determining change in amplitude difference trend;

determining whether there is a change in slope difference trend in response to the comparing of the current determined slope difference trend and a previously determined slope difference trend;

delivering a second therapy in response to determining no change in slope difference trend; and

delivering a third therapy in response to determining change in slope difference trend.