METHOD AND APPARATUS FOR ACCURATELY DETERMINING HEART RATE VARIABILITY AND SYMPATHETIC RESERVE

• US 20150141851A1
• Filed: 02/04/2014
• Published: 05/21/2015
• Est. Priority Date: 11/21/2013
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Sharma, Vinod
• Granted Patent: US 10,736,516 B2
• Time in Patent Office: Days
• US Class Current: 600/483
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/25 Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/333 Recording apparatus specially adapted therefor
• 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

Abstract

An implantable monitoring device is disclosed for monitoring a patient'"'"'s heart rate variability over time. The device includes a cardiac electrogram amplifier, a sensing electrode coupled to an input of the amplifier, timing circuitry, processing circuitry and a memory. The timing circuitry defines successive shorter time periods during each monitoring period. The processing circuitry relies upon electrogram activity that occurs during rest periods that extend as long as T1, all of which is stored into memory. Active periods are not considered as part of the heart rate variability calculation. The processing circuitry calculates median intervals between depolarizations of the patient'"'"'s heart sensed by the amplifier during the shorter time periods and calculates a standard deviation of the median intervals during T2, a longer monitoring period.

Claims

1. A device for monitoring a patient'"'"'s heart rate variability comprising:

a sensing electrode to detect a cardiac depolarization;

a sense amplifier coupled to the sensing electrode to produce a signal indicative of a detected cardiac depolarization;

an activity sensor to generate a signal indicative of activity;

processing means for measuring intervals between successive cardiac depolarizations;

a timing means for defining successive shorter time periods during a longer monitoring period;

processing means for using the signal for determining whether a patient is active;

processing means for using data from the signal for determining rest periods that extend as long as the shorter time period;

processing means for determining cardiac intervals occurring during each rest period;

storing means for storing the measured cardiac intervals;

processing means for calculating a central tendency metric of the measured cardiac intervals during each rest period; and

in response to calculating the central tendency metric, processing means for determining a coefficient of variation of the cardiac intervals during the rest periods within the longer monitoring period to generate the heart rate variability.

2. The device of claim 1 wherein the device is an implantable medical device.

3. The device of claim 1 wherein the device is external to a patient.

4. A device according to claim 1, further comprising means for rejecting measured cardiac depolarization intervals that begin with a paced depolarization.

5. A device according to claim 1, further comprising means for rejecting measured cardiac depolarization intervals occurring during tachyarrhythmias and wherein the calculating means comprises means for calculating median measured cardiac depolarization intervals based only on measured cardiac depolarization intervals not rejected.

6. A device according to claim 5 further comprising means for determining a total duration of the non-rejected measured cardiac depolarization intervals occurring during the shorter time periods, and

means for preventing calculation of a median measured cardiac depolarization interval for the preceding shorter time period if the total duration of non-rejected measured cardiac depolarization intervals during a shorter time period is less than a required duration.

7. A device according to claim 6, further comprising:

processing means for rejecting measured cardiac depolarization intervals occurring during tachyarrhythmias and wherein the calculating step comprises calculating median measured cardiac depolarization intervals based only on measured cardiac depolarization intervals not rejected.

8. A device according to claim 7 wherein the calculating step comprises determining a total duration of the non-rejected measured cardiac depolarization intervals during the shorter time periods and preventing calculation of a median measured cardiac depolariation interval if the total duration of non-rejected heart intervals during a shorter time period is less than a required duration.

9. A device of claim 1 wherein the cardiac interval is a sensed atrial depolarization extending to a next sensed atrial depolarization in a same atria.

10. A device of claim 1 wherein the cardiac interval is a sensed ventricular depolarization extending to a next sensed ventricular depolarization in a same ventricle.

11. A device of claim 1 wherein the cardiac interval is 10 minutes or less.

12. A device of claim 1 wherein the cardiac interval is user programmable interval.

13. A device of claim 1 wherein the coefficient of variation includes standard deviation is just one measure of variability.

14. A computer-implemented method for monitoring a patient'"'"'s heart rate variability comprising:

sensing through an electrode to detect a cardiac depolarization;

producing a signal indicative of the detected cardiac depolarization;

generating a signal indicative of activity;

measuring intervals between successive cardiac depolarizations;

defining successive shorter time periods during a longer monitoring period;

using the signal for determining whether a patient is active;

using data from the signal for determining rest periods that extend as long as the shorter time period;

determining cardiac intervals occurring during each rest period;

storing the measured cardiac intervals;

processing means for calculating a central tendency metric of the measured cardiac intervals during each rest period; and

In response to calculating, the central tendency metric, processing means for determining a coefficient of variation of the cardiac intervals during the rest periods within the longer monitoring period to generate the heart rate variability.

15. The method of claim 14 wherein the method is performed by an implantable medical device.

16. The method of claim 14 wherein the device is external to a patient.

17. The method according to claim 14, further comprising means for rejecting measured cardiac depolarization intervals that begin with a paced depolarization.

18. The method according to claim 14, further comprising means for rejecting measured cardiac depolarization intervals occurring during tachyarrhythmias and wherein the calculating means comprises means for calculating median measured cardiac depolarization intervals based only on measured cardiac depolarization intervals not rejected.

19. A method according to claim 14, further comprising:

processing means for rejecting measured cardiac depolarization intervals occurring during tachyarrhythmias.

20. A non-transitory machine readable medium containing executable computer program instructions which when executed by a data processing system cause the system to perform a method of determining heart rate variability, the method comprising:

sensing through an electrode to detect a cardiac depolarization;

producing a signal indicative of the detected cardiac depolarization;

generating a signal indicative of activity;

measuring intervals between successive cardiac depolarizations;

defining successive shorter time periods during a longer monitoring period;

using the signal for determining whether a patient is active;

using data from the signal for determining rest periods that extend as long as the shorter time period;

determining cardiac intervals occurring during each rest period;

storing the measured cardiac intervals;

calculating an average of the measured cardiac intervals during each rest period; and

in response to calculating the average of the measured cardiac intervals, processing means for determining a coefficient of variation of the cardiac intervals during the rest periods within the longer monitoring period to generate the heart rate variability.

21. The medium as in claim 20, further comprising means for rejecting measured cardiac depolarization intervals that begin with a paced depolarization.

22. The medium as in claim 20, further comprising means for rejecting measured cardiac depolarization intervals occurring during tachyarrhythmias and wherein the calculating means comprises means for calculating median measured cardiac depolarization intervals based only on measured cardiac depolarization intervals not rejected.

23. A device for monitoring a patient'"'"'s heart rate variability consisting essentially of:

a sensing electrode to detect a cardiac depolarization;

a sense amplifier coupled to the sensing electrode to produce a signal indicative of a detected cardiac depolarization;

an activity sensor to generate an activity signal indicative of activity;

processing means for measuring intervals between successive cardiac depolarizations;

a timing means for defining successive shorter time periods during a longer monitoring period;

processing means for using the activity signal for determining whether a patient is active;

processing means for using data from the activity signal for determining rest periods that extend as long as the shorter time period;

processing means for determining cardiac intervals occurring solely during each rest period;

storing means for storing the measured cardiac intervals;

processing means for calculating an median or average of the measured cardiac intervals during each rest period; and

in response to calculating the median or the average, processing means for calculating standard deviation within the rest periods.

24. The device of claim 23 wherein the cardiac interval is a sensed atrial depolarization extending to a next sensed atrial depolarization in a same atria.

25. The device of claim 23 wherein the cardiac interval is a sensed ventricular depolarization extending to a next sensed ventricular depolarization in a same ventricle.

26. An implantable medical device for monitoring a patient'"'"'s heart rate variability comprising:

a sensing electrode to detect a cardiac depolarization;

a sense amplifier electrically coupled to the sensing electrode to produce a signal indicative of a detected cardiac depolarization, the sense amplifier associated with amplifying P waves;

an activity sensor to generate an activity signal indicative of activity;

processing means for measuring intervals between successive cardiac depolarizations, the interval being defined as a sensed atrial depolarization extending to a next sensed atrial depolarization in a same atria;

a timing means for defining successive shorter time periods during a longer monitoring period;

processing means for using the activity signal for determining whether a patient is active;

processing means for using data from the activity signal for determining rest periods that extend as long as the shorter time period;

processing means for determining cardiac intervals occurring solely during each rest period;

storing means for storing the measured cardiac intervals;

processing means for calculating a central tendency metric of the measured cardiac intervals during each rest period; and

processing means for determining a coefficient of variation of the cardiac intervals during the rest periods within the longer monitoring period to generate the heart rate variability.

27. A device of claim 26 wherein the cardiac interval is 10 minutes or less.

28. A device of claim 26 wherein the cardiac interval is user programmable interval.

29. A device of claim 26 wherein the coefficient of variation includes standard deviation is just one measure of variability.

30. A device for monitoring a patient'"'"'s heart rate variability comprising:

a sensing electrode to detect a cardiac depolarization;

a sense amplifier coupled to the sensing electrode to produce a signal indicative of a detected cardiac depolarization;

an activity sensor to generate a signal indicative of activity;

processing means for measuring intervals between successive cardiac depolarizations;

a timing means for defining successive shorter time periods during a longer monitoring period;

processing means for using the signal for determining whether a patient is active;

processing means for using data from the signal for determining rest periods that extend as long as the shorter time period;

processing means for determining cardiac intervals occurring during each rest period;

storing means for storing the measured cardiac intervals;

processing means for calculating a central tendency metric of the measured cardiac intervals during each rest period; and

in response to calculating the central tendency metric, processing means for determining a coefficient of variation of the cardiac intervals during the rest periods within the longer monitoring period to generate the heart rate variability,

wherein the measured interval is solely sensed atrial depolarizations sensed in a same atria.

31. A device for monitoring a patient'"'"'s heart rate variability comprising:

a sensing electrode to detect a cardiac depolarization;

a sense amplifier coupled to the sensing electrode to produce a signal indicative of a detected cardiac depolarization;

an activity sensor to generate a signal indicative of activity;

processing means for measuring intervals between successive cardiac depolarizations;

a timing means for defining successive shorter time periods during a longer monitoring period;

processing means for using the signal for determining whether a patient is active;

processing means for using data from the signal for determining rest periods that extend as long as the shorter time period;

processing means for determining cardiac intervals occurring during each rest period;

storing means for storing the measured cardiac intervals;

processing means for calculating a central tendency metric of the measured cardiac intervals during each rest period; and

in response to calculating the central tendency metric, processing means for determining a coefficient of variation of the cardiac intervals during the rest periods within the longer monitoring period to generate the heart rate variability,

wherein the measured interval is solely sensed ventricular depolarizations sensed in a same ventricle.