RESPIRATORY PARAMETERS FOR ARRHYTHMIA DETECTION AND THERAPY

• US 20120197323A1
• Filed: 01/19/2012
• Published: 08/02/2012
• Est. Priority Date: 02/02/2011
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Hopper, Donald L., Seim, Gary T., Gilkerson, James O., Li, Dan, Perschbacher, David L., Elferri, Efdal, McPherson, Randall L.
• Granted Patent: US 8,639,324 B2
• Time in Patent Office: Days
• US Class Current: 607/4
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/091 Measuring volume of inspired or expired gases, e.g. to determine lung capacity
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/39622 Pacing therapy

Abstract

An implantable or ambulatory medical device can include a cardiac signal sensing circuit configured to provide a sensed cardiac depolarization signal of a heart of a subject, a respiration sensing circuit configured to provide a signal representative of respiration of the subject, and a control circuit communicatively coupled to the cardiac signal sensing circuit and the respiration circuit. The control circuit includes a tachyarrhythmia detection circuit configured to determine heart rate using the depolarization signal, determine a respiration parameter of the subject using the respiration signal, calculate a ratio using the determined heart rate and the determined respiration parameter, generate an indication of tachyarrhythmia when the calculated ratio satisfies a specified detection ratio threshold value, and provide the indication of tachyarrhythmia to a user or process.

Claims

1. An implantable or other ambulatory medical apparatus comprising:

a cardiac signal sensing circuit configured to provide a sensed cardiac depolarization signal of a heart of a subject;

a respiration sensing circuit configured to provide a signal representative of respiration of the subject; and

a control circuit communicatively coupled to the cardiac signal sensing circuit and the respiration circuit, wherein the control circuit includes a tachyarrhythmia detection circuit configured to;

determine heart rate using the depolarization signal;

determine a respiration parameter of the subject using the respiration signal;

calculate a ratio using the determined heart rate and the determined respiration parameter;

generate an indication of tachyarrhythmia when the calculated ratio satisfies a specified tachyarrhythmia detection ratio threshold value; and

provide the indication of tachyarrhythmia to a user or process.

2. The apparatus of claim 1,

wherein the tachyarrhythmia detection circuit includes a minute ventilation (MV) circuit configured to determine MV from the respiration signal as the respiration parameter, and

wherein the tachyarrhythmia detection circuit is configured to calculate the ratio using the determined heart rate and the determined MV.

3. The apparatus of claim 2, wherein the tachyarrhythmia detection circuit is configured to:

compare the determined heart rate to a specified lowest tachyarrhythmia rate (LTR) detection threshold value, and

calculate the ratio when the determined heart rate satisfies the specified LTR detection threshold.

4. The apparatus of claim 3, including:

a therapy circuit communicatively coupled to the control circuit and configured to selectively deliver electrical cardioversion/defibrillation shock therapy and electrical pacing stimulation energy to the heart;

wherein the control circuit is configured to;

initiate delivery of cardioversion/defibrillation shock therapy in response to the indication of tachyarrhythmia when the calculated ratio satisfies the tachyarrhythmia detection ratio threshold value; and

initiate delivery of anti-tachyarrhythmia pacing (ATP) therapy in response to the indication of tachyarrhythmia otherwise.

5. The apparatus of claim 3, wherein the tachyarrhythmia detection circuit is configured to generate an indication of tachyarrhythmia when the determined heart rate and the calculated ratio satisfy the LTR detection threshold and the specified detection ratio threshold, respectively, for a specified minimum detection time duration threshold value.

6. The apparatus of claim 2, wherein the MV circuit is configured to:

extract respiration rate from the respiration signal;

determine tidal volume using the respiration signal; and

calculate MV of the subject using the respiration rate and tidal volume.

7. The apparatus of claim 2, including:

a memory circuit integral to, or communicatively coupled to, the control circuit,

wherein the tachyarrhythmia detection circuit is configured to;

compare the determined heart rate to a specified lowest tachyarrhythmia rate (LTR) detection threshold value;

generate an indication of slow tachyarrhythmia when the heart rate is less than the specified LTR detection threshold value and the calculated ratio satisfies a specified detection ratio threshold value; and

store the indication of slow tachyarrhythmia using the memory circuit.

8. The apparatus of claim 1, including:

an activity sensing circuit configured to provide a signal representative of activity of the subject;

wherein the tachyarrhythmia detection circuit is configured to;

detect that the determined heart rate satisfies a specified LTR detection threshold value;

generate an indication of tachyarrhythmia when the calculated ratio satisfies the specified detection ratio threshold value; and

generate an indication of activity-induced tachyarrhythmia when the specified detection ratio threshold value is not satisfied and an activity level indicated by the activity signal exceeds an activity level threshold value.

9. The apparatus of claim 1, wherein the respiration sensing circuit includes an intra-thoracic impedance sensing circuit configured to provide an impedance signal representative of respiration of the subject.

10. The apparatus of claim 1, wherein the respiration sensing circuit includes an accelerometer, and wherein respiration signal includes an acceleration signal representative of motion of the thorax region of the subject.

11. A method of operating an ambulatory or implantable medical device, the method comprising:

determining heart rate of a subject;

determining a respiration parameter of the subject;

calculating a ratio using the determined heart rate and the determined respiration parameter; and

generating an indication of tachyarrhythmia when the calculated ratio satisfies a specified detection ratio threshold value and providing the indication of the tachyarrhythmia to a user or process.

12. The method of claim 11, wherein determining the respiration parameter includes determining MV for the subject.

13. The method of claim 12, including:

determining that the heart rate satisfies a specified lowest tachyarrhythmia rate (LTR) detection threshold value, and

wherein calculating the ratio includes calculating the ratio when the heart rate satisfies the specified LTR detection threshold.

14. The method of claim 13, including:

initiating delivery of cardioversion/defibrillation shock therapy with the device when the calculated ratio satisfies the tachyarrhythmia detection ratio threshold value; and

initiating delivery of anti-tachyarrhythmia pacing (ATP) therapy otherwise.

15. The method of claim 13, wherein generating an indication of tachyarrhythmia includes generating an indication of tachyarrhythmia when the determined heart rate and the calculated ratio satisfy the LTR detection threshold and the specified detection ratio threshold, respectively, for a specified minimum detection time duration threshold value.

16. The method of claim 12, including:

determining that the heart rate is less than a specified lowest tachyarrhythmia rate (LTR) detection threshold value; and

generating an indication of slow tachyarrhythmia when the heart rate is less than the specified LTR detection threshold value and the calculated ratio satisfies a specified detection ratio threshold value.

17. The method of claim 12, including:

monitoring activity of the subject;

detecting an episode of tachyarrhythmia during a period of subject activity;

generating an indication of tachyarrhythmia for the episode when the calculated ratio satisfies the specified detection ratio threshold value; and

generating an indication of activity-induced tachyarrhythmia for the episode otherwise.

18. The method of claim 12, wherein determining MV includes:

sensing a physiologic signal representative of respiration using the device;

extracting respiration rate from the physiologic signal representative of respiration;

determining tidal volume using the physiologic signal representative of respiration; and

calculating MV of the subject using the respiration rate and tidal volume.

19. The method of claim 18, wherein sensing a physiologic signal representative of respiration includes sensing an intra-thoracic impedance signal using the device.

20. The method of claim 18, wherein sensing a physiologic signal representative of respiration includes sensing motion of the thorax region of the subject using an accelerometer.