SENSOR RESPONSE DELAY FOR HEMODYNAMIC STABILITY DETECTION DURING ARRHYTHMIA

• US 20120303078A1
• Filed: 05/09/2012
• Published: 11/29/2012
• Est. Priority Date: 05/23/2011
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Li, Dan, Brisben, Amy Jean
• Granted Patent: US 8,812,102 B2
• Time in Patent Office: Days
• US Class Current: 607/4
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61N 1/36507 controlled by gradient or slope of the heart potential
• CPC Class Codes: A61N 1/36578 controlled by mechanical motion of the heart wall, e.g. measured by an accelerometer or microphone
• CPC Class Codes: A61N 1/36585 controlled by two or more physical parameters
• CPC Class Codes: A61N 1/3956 Implantable devices for applying electric shocks to the heart, e.g. for cardioversion

Abstract

An apparatus comprises a cardiac signal sensing circuit, a physiologic sensor circuit configured to provide a physiologic sensor signal representative of mechanical cardiac activity, a therapy circuit, and a control circuit. The control circuit includes a cardiac depolarization detection circuit, a tachyarrhythmia detection circuit, and a timer circuit. A time interval between a mechanical cardiac event and a detected fiducial electrical cardiac event is monitored. The control circuit is configured to correct the monitored time interval for variation with heart rate to form a corrected electromechanical time interval, initiate anti-tachyarrhythmia therapy when the corrected electromechanical time interval satisfies a specified time interval threshold value during a detected episode of tachyarrhythmia, and withhold anti-tachyarrhythmia therapy otherwise.

Claims

1. An apparatus comprising:

a cardiac signal sensing circuit configured to provide a cardiac signal representative of electrical cardiac activity;

a physiologic sensor circuit configured to provide a physiologic sensor signal representative of mechanical cardiac activity;

a therapy circuit configured to provide anti-tachyarrhythmia therapy; and

a control circuit communicatively coupled to the cardiac signal sensing circuit, the physiologic sensor circuit, and the therapy circuit, wherein the control circuit includes;

a cardiac depolarization detection circuit configured to detect a cardiac depolarization using at least one of the cardiac signal and the physiologic sensor signal;

a tachyarrhythmia detection circuit; and

a timer circuit configured to monitor a time interval between a mechanical cardiac event and a detected fiducial electrical cardiac event; and

wherein the control circuit is configured to;

correct the monitored time interval for variation with heart rate to form a corrected electromechanical time interval;

initiate anti-tachyarrhythmia therapy when the corrected electromechanical time interval satisfies a specified time interval threshold value during a detected episode of tachyarrhythmia; and

withhold anti-tachyarrhythmia therapy otherwise.

2. The apparatus of claim 1, wherein the control circuit is configured to calculate a corrected time interval using a ratio that includes a measured cardiac depolarization interval and the time interval between the mechanical cardiac event and the fiducial electrical cardiac event.

3. The apparatus of claim 1, wherein the control circuit is configured to:

establish a baseline electromechanical time interval during normal sinus rhythm (NSR); and

normalize a value of the electromechanical time interval measured during the episode of tachyarrhythmia with the baseline electromechanical time interval.

4. The apparatus of claim 1,

wherein the therapy circuit is configured to provide cardioversion/defibrillation shock therapy and anti-tachyarrhythmia pacing (ATP) therapy, and

wherein the control circuit is configured to:

initiate cardioversion/defibrillation shock therapy when detecting a change in the time interval during the episode of tachyarrhythmia that satisfies the specified time interval change threshold; and

initiate anti-tachyarrhythmia pacing (ATP) therapy when detecting a change in the time interval during the episode of tachyarrhythmia that does not satisfy the specified time interval change threshold.

5. The apparatus of claim 1,

wherein the therapy circuit is configured to provide cardioversion/defibrillation shock therapy and anti-tachyarrhythmia pacing (ATP) therapy, and

wherein the control circuit is configured to:

initiate anti-tachyarrhythmia pacing (ATP) therapy when the time interval satisfies a first time interval change threshold during the episode of tachyarrhythmia; and

initiate cardioversion/defibrillation shock therapy when the time interval satisfies a second time interval change threshold during the episode of tachyarrhythmia.

6. The apparatus of claim 1, wherein the control circuit is configured to:

establish a baseline for the corrected time interval between a mechanical cardiac event and a fiducial electrical cardiac event; and

initiate anti-tachyarrhythmia therapy when detecting, during the episode of tachyarrhythmia, a change in the corrected time interval from the baseline time interval that satisfies a specified time interval change threshold.

7. The apparatus of claim 1,

wherein the timer circuit is configured to monitor the electromechanical time interval after delivery of the anti-tachyarrhythmia therapy;

and

wherein the control circuit is configured to re-initiate the anti-tachyarrhythmia therapy when the corrected electromechanical time interval satisfies the same or a different time interval change threshold.

8. The apparatus of claim 1,

wherein physiologic sensor circuit includes a cardiac pressure sensing circuit, and

wherein the timer circuit is configured to monitor a time interval between the detected fiducial electrical cardiac event and a detected fiducial in systolic pressure.

9. The apparatus of claim 8, wherein the cardiac pressure sensing circuit is configured for placement in or near at least one of the right ventricle, the left ventricle, and the pulmonary artery.

10. The apparatus of claim 1,

wherein the physiologic sensor circuit includes a heart sound sensing circuit, and

wherein the timer circuit is configured to monitor a time interval between the detected fiducial electrical cardiac event and a measurement of a detected heart sound.

11. The apparatus of claim 1,

wherein the physiologic sensor circuit includes a cardiac impedance sensing circuit, and

wherein the timer circuit is configured to monitor a time interval between the detected fiducial electrical cardiac event and a detected fiducial in cardiac impedance.

12. A method of operating an implantable medical device, the method comprising:

monitoring a time interval between a detected mechanical cardiac event and a detected fiducial electrical cardiac event;

detecting an episode of tachyarrhythmia;

correcting the monitored time interval for variation with heart rate to form a corrected electromechanical time interval;

initiating anti-tachyarrhythmia therapy when the corrected electromechanical time interval satisfies a specified time interval threshold value during the episode of tachyarrhythmia; and

withholding anti-tachyarrhythmia therapy otherwise.

13. The method of claim 12, wherein correcting the time interval includes forming a ratio using the monitored time interval and one of a measured heart rate or a measured heart beat interval.

14. The method of claim 12, wherein correcting the time interval includes:

determining a baseline electromechanical time interval during normal sinus rhythm (NSR), and

wherein correcting the time interval includes normalizing a value of the electromechanical time interval measured during the episode of tachyarrhythmia with the baseline electromechanical time interval.

15. The method of claim 12, wherein initiating anti-tachyarrhythmia therapy includes:

initiating cardioversion/defibrillation shock therapy when detecting, during the episode of tachyarrhythmia, a change in the time interval that satisfies the specified time interval change threshold; and

initiating anti-tachyarrhythmia pacing (ATP) therapy when detecting a change in the time interval during the episode of tachyarrhythmia that does not satisfy the specified time interval change threshold.

16. The method of claim 12, wherein initiating anti-tachyarrhythmia therapy includes:

initiating anti-tachyarrhythmia pacing (ATP) therapy when the time interval satisfies a first specified time interval change threshold during the episode of tachyarrhythmia; and

initiating cardioversion/defibrillation shock therapy when the time interval satisfies a second specified time interval change threshold during the episode of tachyarrhythmia.

17. The method of claim 16, including adjusting a parameter of the initiated therapy according to the monitored time interval.

18. The method of claim 12, wherein monitoring a time interval includes monitoring a time interval between the detected fiducial electrical cardiac event and a detected fiducial in at least one of a signal representative of cardiac impedance and a signal representative of right ventricular systolic pressure.

19. The method of claim 12, wherein monitoring a time interval includes monitoring a time interval between the detected fiducial electrical cardiac event and a detected fiducial of a heart sound signal.

20. The method of claim 12,

wherein monitoring a time interval includes monitoring a baseline time interval between the fiducial electrical cardiac event and a fiducial of the mechanical cardiac event, and

wherein initiating anti-tachyarrhythmia therapy includes initiating anti-tachyarrhythmia therapy when detecting, during the episode of tachyarrhythmia, a change in the time interval from the baseline time interval that satisfies a specified time interval change threshold.