STAGED RHYTHM DETECTION SYSTEM AND METHOD

• US 20140323894A1
• Filed: 04/15/2014
• Published: 10/30/2014
• Est. Priority Date: 04/26/2013
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Zhang, Xusheng, Brown, Mark L, Greenhut, Saul E, Stadler, Robert W
• Granted Patent: US 9,775,559 B2
• Time in Patent Office: Days
• US Class Current: 600/518
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61N 1/3621 for treating or preventing abnormally high heart rate
• CPC Class Codes: A61N 1/3702 Physiological parameters A61N1/365 takes precedence; evoked response A61N1/371
• CPC Class Codes: A61N 1/37264 Changing the program; Upgrading firmware
• CPC Class Codes: A61N 1/37282 characterised by communication with experts in remote locations using a network
• CPC Class Codes: A61N 1/385 Devices for inducing an abnormal cardiac function, e.g. fibrillation

Abstract

A medical device and associated method for detecting and treating tachyarrhythmias acquires a cardiac signal using electrodes coupled to a sensing module. During an initial detection process, a shockable cardiac rhythm is detected by a processing module configured to compare the cardiac signal to a first set of detection criteria. By analyzing the cardiac signal, the processing module establishes at least one patient-specific detection threshold during the initial detection process. Upon establishing the at least one patient-specific detection threshold, the initial detection process is stopped, and a next detection process is started which includes comparing the cardiac signal to a second set of detection criteria including the at least one patient-specific detection threshold. In some embodiments, user programming of tachyarrhythmia detection parameters is not required.

Claims

1. A method for use in a medical device configured to detect and treat tachyarrhythmia, the method comprising:

acquiring a cardiac signal using a plurality of electrodes coupled to a sensing module;

during an initial detection process detecting a shockable cardiac rhythm by a processing module configured to compare the cardiac signal to a first set of detection criteria;

establishing, by the processing module analyzing the cardiac signal, at least one patient-specific detection threshold during the initial detection process; and

upon establishing the at least one patient-specific detection threshold, stopping the initial detection process and starting a next detection process comprising comparing the cardiac signal to a second set of detection criteria comprising the at least one patient-specific detection threshold,

the first set of detection criteria relating to a first set of cardiac signal features, the second set of detection criteria relating to a second set of cardiac signal features different than the first set of cardiac signal features.

2. The method of claim 1, wherein the first set of detection criteria comprises only population-based detection thresholds.

3. The method of claim 1, wherein comparing the cardiac signal to a first set of detection criteria comprises determining a gross morphology feature of the cardiac signal over a predetermined time interval independent of a timing of a cardiac cycle.

4. The method of claim 1, wherein establishing the at least one patient-specific detection threshold comprises determining a beat feature of the cardiac signal representative of a cardiac cycle.

5. The method of claim 1, further comprising determining a beat feature of a cardiac cycle of the cardiac signal during the next detection process that is not determined during the initial detection process and comparing the beat feature to one of the patient-specific detection thresholds.

6. The method of claim 1, further comprising detecting a concerning cardiac rhythm during a first stage of the next detection process;

and

discriminating the concerning cardiac rhythm as one of a shockable rhythm and a non-shockable rhythm during a second stage of the next detection process.

7. The method of claim 6, further comprising updating the at least one patient-specific detection threshold during the first stage when a concerning cardiac rhythm is not being detected.

8. The method of claim 6, wherein discriminating the concerning cardiac rhythm comprises:

determining a cardiac cycle feature and in a first comparison comparing the cardiac cycle feature to one of the patient-specific thresholds;

determining a gross morphology feature across a cardiac signal segment and in a second comparison comparing the gross morphology feature to a population-based threshold.

9. The method of claim 8, further comprising:

rating a first confidence of the first comparison;

rating a second confidence of the second comparison; and

adjusting one of the patient-specific threshold and the population-based threshold in response to comparing the first confidence and the second confidence ratings.

10. The method of claim 1, wherein establishing the patient specific threshold comprises:

setting a learning window;

confirming the learning window corresponds to a non-shockable rhythm using a non-ECG signal;

determining a feature of the cardiac signal for multiple cardiac cycles during the learning window; and

setting the patient-specific threshold in response to the feature.

11. The method of claim 1, further comprising:

setting a learning window;

determining a feature of the cardiac signal for multiple cardiac cycles during the learning window;

setting the patient-specific threshold in response to the feature; and

selecting at least one of a sensing vector and a decay rate of a sensing threshold in response to the feature.

12. The method of claim 1, further comprising:

setting a learning window;

determining a similarity between cycles of the cardiac signal over the learning window;

determining a feature of the cardiac signal for multiple cardiac cycles during the learning window if the similarity meets a correlation requirement; and

setting the patient-specific threshold in response to the feature.

13. The method of claim 1, further comprising:

determining a feature of the cardiac signal;

comparing the feature to a historic value of the feature;

updating the historic value of the feature if the determined feature is within a range of the historic value; and

setting the patient-specific threshold in response to the updated historic value,

the range being adjusted to a relatively narrower range as the historic value is updated over time.

14. The method of claim 1, further comprising performing the initial detection process and the next detection process without a user-programmed detection parameter.

15. A medical device for detecting and treating tachyarrhythmia, comprising:

a plurality of electrodes for acquiring a cardiac signal;

a sensing module coupled to the plurality of electrodes for sensing cardiac events in response to the cardiac signal; and

a processing module configured to;

perform an initial detection process comprising detecting a shockable cardiac rhythm by comparing the cardiac signal to a first set of detection criteria;

establish, by analyzing the cardiac signal, at least one patient-specific detection threshold during the initial detection process; and

upon establishing the at least one patient-specific detection threshold, stop the initial detection process and start a next detection process comprising comparing the cardiac signal to a second set of detection criteria comprising the at least one patient-specific detection threshold,

the first set of detection criteria relating to a first set of cardiac signal features, the second set of detection criteria relating to a second set of cardiac signal features different than the first set of cardiac signal features.

16. The device of claim 15, wherein the first set of detection criteria comprises only population-based detection thresholds.

17. The device of claim 15, wherein comparing the cardiac signal to a first set of detection criteria comprises determining a gross morphology feature of the cardiac signal over a predetermined time interval independent of a timing of a cardiac cycle.

18. The device of claim 15, wherein establishing the at least one patient-specific detection threshold comprises determining a beat feature of the cardiac signal representative of a cardiac cycle.

19. The device of claim 15, wherein the processing module is further configured to determine a beat feature of a cardiac cycle of the cardiac signal during the next detection process that is not determined during the initial detection process and compare the beat feature to one of the patient-specific detection thresholds.

20. The device of claim 15, wherein the processing module is further configured to detect a concerning cardiac rhythm during a first stage of the next detection process;

and

discriminate the concerning cardiac rhythm as one of a shockable rhythm and a non-shockable rhythm during a second stage of the next detection process.

21. The device of claim 20, wherein the processing module is further configured to update the at least one patient-specific detection threshold during the first stage when a concerning cardiac rhythm is not being detected.

22. The device of claim 20, wherein the processing module is configured to discriminate the concerning cardiac rhythm by:

determining a cardiac cycle feature and in a first comparison compare the cardiac cycle feature to one of the patient-specific thresholds;

determining a gross morphology feature across a cardiac signal segment and in a second comparison compare the gross morphology feature to a population-based threshold.

23. The device of claim 22, wherein the processing module is further configured to:

rate a first confidence of the first comparison;

rate a second confidence of the second comparison; and

adjust one of the patient-specific threshold and the population-based threshold in response to comparing the first confidence and the second confidence ratings.

24. The device of claim 15, wherein the processing module is configured to establish the patient specific threshold by:

setting a learning window;

confirming the learning window corresponds to a non-shockable rhythm using a non-ECG signal;

determining a feature of the cardiac signal for multiple cardiac cycles during the learning window; and

setting the patient-specific threshold in response to the feature.

25. The device of claim 15, wherein the processing module is configured to:

set a learning window;

determine a feature of the cardiac signal for multiple cardiac cycles during the learning window;

set the patient-specific threshold in response to the feature; and

select at least one of a sensing vector and a decay rate of a sensing threshold in response to the feature.

26. The device of claim 15, wherein the processing module is configured to:

set a learning window;

determine a similarity between cycles of the cardiac signal over the learning window;

determine a feature of the cardiac signal for multiple cardiac cycles during the learning window if the similarity meets a correlation requirement; and

set the patient-specific threshold in response to the feature.

27. The device of claim 15, wherein the processing module is configured to:

determine a feature of the cardiac signal;

compare the feature to a historic value of the feature;

update the historic value of the feature if the determined feature is within a range of the historic value; and

set the patient-specific threshold in response to the updated historic value,

the range being adjusted to a relatively narrower range as the historic value is updated over time.

28. The device of claim 15, wherein the processing module is configured to perform the initial detection process and the next detection process without a user-programmed detection parameter.

29. A non-transitory, computer-readable storage medium storing a set of instructions, which when executed by a processor of a medical device causes the device to:

acquire a cardiac signal using a plurality of electrodes coupled to a sensing module;

during an initial detection process, detect a shockable cardiac rhythm by comparing the cardiac signal to a first set of detection criteria;

establish, by analyzing the cardiac signal, at least one patient-specific detection threshold during the initial detection process; and

upon establishing the at least one patient-specific detection threshold, stop the initial detection process and start a next detection process comprising comparing the cardiac signal to a second set of detection criteria comprising the at least one patient-specific detection threshold,

the first set of detection criteria relating to a first set of cardiac signal features, the second set of detection criteria relating to a second set of cardiac signal features different than the first set of cardiac signal features.