QT INTERVAL DETERMINATION METHODS AND RELATED DEVICES

• US 20160135708A1
• Filed: 11/17/2014
• Published: 05/19/2016
• Est. Priority Date: 11/17/2014
• Status: Active Grant

• Current Assignee: Medtronic Monitoring, Inc. (Medtronic Plc)
• Original Assignee: Medtronic Monitoring, Inc. (Medtronic Plc)
• Inventors: GUDIVADA, Rao, CHAKRAVARTHY, Niranjan, CHAVAN, Abhi, WILLIAMS, Scott
• Granted Patent: US 9,986,932 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/36 Detecting PQ interval, PR interval or QT interval
• CPC Class Codes: A61B 5/366 Detecting abnormal QRS complex, e.g. widening
• CPC Class Codes: A61B 5/6823 Trunk, e.g., chest, back, abdomen, hip
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment

Abstract

Described herein is a system and method of automatically monitoring QT intervals in a patient based on one or more EKG signals received from attached monitoring devices. Each EKG signal is analyzed to detect attributes of the first and second EKG signals, including QRS onset information, QRS peak information, and T-wave offset information. A QT interval is calculated based on QRS onset information derived from the first EKG signal and T-wave offset information derived from the second EKG signal. The calculated QT interval is compared to thresholds to detect elongation of the QT interval and an alert is generated in response to a detected elongated QT interval.

Claims

1. A monitoring system for measuring QT intervals in patients, the monitoring system comprising:

a first monitoring device adhered to a patient at a first location that monitors a first electrocardiogram (EKG) signal associated with the patient;

a QT interval measurement module configured to receive the first EKG signal from the first monitoring device, wherein the QT interval measurement module;

identifies QRS complex attributes and heart rate attributes for each beat within the received first EKG signal;

locates based on identified QRS complex and heart rate attributes a T-wave offset (iToff) for each beat;

selects qualified beat segments comprised of a plurality of beats suitable for QT interval measurement within the received first EKG signal; and

measures QT intervals within the qualified beat segments based on QRS complex attributes and T-wave offsets identified with respect to each beat.

2. The monitoring system of claim 1, wherein identification of QRS complex attributes includes QRS peak (iRpk) and QRS onset (iRon) attributes.

3. The monitoring system of claim 2, wherein measurement of the QT interval is calculated as an interval between the QRS peak (iRpk) and the T-wave offset (iToff).

4. The monitoring system of claim 1, wherein locating the T-wave offset for each beat includes utilizing the identified heart rate of the patient and a look-up table to estimate a T-wave offset window in which to search for the T-wave offset.

5. The monitoring system of claim 4, wherein minimum and maximum values within the defined T-wave offset window are identified and utilized to detect the T-wave offset with respect to each beat.

6. The monitoring system of claim 1, wherein the selection of qualified beat segments includes selecting a consecutive number of non-noisy beats, wherein a number of beats required is set by a threshold.

7. The monitoring system of claim 1, wherein the QT interval measurement module is located in an intermediate device that includes a processor for executing instructions stored in a computer readable medium, and an antenna for receiving the first EKG signal from the first monitoring device.

8. The monitoring system of claim 1, wherein the QT interval measurement module generates an alert in response to detected long QT intervals.

9. The monitoring system of claim 8, wherein the QT interval measurement module provides generated alerts and the received first EKG signal to a remote monitoring center.

11. The monitoring system of claim 7, wherein the first attributes associated with the first EKG signal includes onset of the QRS complex (iRon_a) and QRS complex peak (iRpk_a), and wherein the second attributes associated with the second EKG signal includes QRS complex peak (iRpk_b) and T-wave offset (iToff_b).

12. The monitoring system of claim 11, wherein the QT interval is measured based on the equation:

iQT=(iRpk_a−

iRon_a)+(iToff_b−

Rpk_b).

10. A monitoring system for measuring QT intervals in patients, the monitoring system comprising:

a first monitoring device adhered to a patient at a first location that monitors a first electrocardiogram (EKG) signal associated with the patient;

a second monitoring device adhered to a patient at a second location different than the first location that monitors a second EKG signal associated with the patient;

a QT interval measurement module configured to receive the first and second EKG signals from the first and second monitoring devices, respectively, wherein the QT interval measurement module;

identifies first attributes associated with the first EKG signal and second attributes associated with the second EKG signal;

selects qualified beat segments comprised of a plurality of beats suitable for QT interval measurement within the received first and second EKG signals; and

measures QT intervals within the qualified beat segments based on a combination of the first attributes associated with the first EKG signal and second attributes associated with the second EKG signal.

13. The monitoring system of claim 10, wherein both the first monitoring device and the second monitoring device receiving timing information from an external source, wherein first and second EKG signals include timestamps based on the received timing information.

14. The monitoring system of claim 13, wherein the first EKG signal and the second EKG signal are aligned based on timestamps associated with both EKG signals.

15. The monitoring system of claim 10, wherein qualified beats within the first EKG signal are selected and a search is conducted within the second EKG signal to locate a qualified segment of beats that can be aligned with the qualified beats within the first EKG signal.

16. The monitoring system of claim of 15, wherein alignment between qualified beats within the first EKG signal and qualified beats within the second EKG signal are based on criterion that include one or more of minimum threshold interval of time between aligned QRS peaks and percentage of peaks aligned within a segment of beats.

17. The monitoring system of claim 10, wherein the QT interval measurement module is located in an intermediate device that includes a processor for executing instructions stored in a computer readable medium, and an antenna for receiving the first EKG signal from the first monitoring device.

18. The monitoring system of claim 10, wherein the QT interval measurement module generates an alert in response to detected long QT intervals.

19. The monitoring system of claim 18, wherein the QT interval measurement module provides generated alerts and the received first EKG signal to a remote monitoring center.

20. A method of automatically monitoring QT intervals in a patient, the method comprising:

receiving global timing information at a first adherent device and a second adherent device;

measuring a first electrocardiogram (EKG) signal using the first adherent device affixed to the patient at a first lead location and associating a timestamp with the first EKG signal based on received global timing information;

measuring a second EKG signal using the second adherent device affixed to the patient at a second lead location and associating a timestamp with the second EKG signal based on received global timing information;

communicating the first and second measured EKG signals and timestamp information from the first and second adherent devices, respectively, to a processor system;

calculating a QT interval based on the first and second EKG signals, wherein the QT interval is calculated based on QRS onset information derived from the first EKG signal and T-wave offset information derived from the second EKG signal; and

comparing the calculated QT interval to thresholds to detect elongation of the QT interval and generating an alert in response to a detected elongated QT interval provided as an output of the processor system.

21. The method of claim 20, further including selecting a string of beats within the first measured EKG signal qualified for estimating QT intervals, wherein the qualified string of beats is selected that meets both a noise level threshold and heart rate variation threshold.

22. The method of claim 21, wherein the heart rate variation threshold is identified as a difference between a maximum heart rate and a minimum heart rate within the first string of beats is less than five beats per minute.

23. The method of claim 20, wherein the first adherent device is located on the patient'"'"'s abdomen and the second adherent device is located on the patient'"'"'s chest at a forty-five degree angle to the first device.

24. The method of claim 20, wherein calculating a QT interval based on the selected qualified beats is defined by the equation:

iQT=(iRpk_a−

iRon_a)+(iToff_b−

iRpk_b), wherein iQT is the QT interval, iRpk_a is the QRS peak of a qualified beat associated with the first EKG signal, iRon_a is the onset of the QRS complex of a qualified beat associated with the first EKG signal, iToff_b is the T-wave offset of a qualified beat associated with the second EKG signal, and iRpk_b is the QRS peak of a qualified beat associated with the second EKG signal.

25. A method of detecting QT intervals, the method comprising:

receiving a first electrocardiogram (EKG) signal from a first device located in a first lead configuration on a patient'"'"'s abdomen;

receiving a second EKG signal from a second device located in a second lead configuration located on the patient'"'"'s chest at a defined angle relative to the first device;

detecting QRS onset and QRS peak information with respect to the first EKG signal and QRS peak and T-wave offset information with respect to the second EKG signal;

matching a first plurality of beats associated with the first measured EKG signal with a second plurality of beats associated with the second EKG signal to align the QRS peaks of the first plurality of beats with the QRS peaks of the second plurality of beats;

calculating a QT interval based on the detected QRS onset information associated with the first EKG signal and T-wave offset information associated with the second EKG signal; and

detecting abnormalities in the QT interval based on the calculated QT interval.

26. The method of claim 25, wherein matching the first plurality of beats associated with the first measured EKG signal with the second plurality of beats associated with the second EKG signal includes:

identifying a first string of beats in the first EKG signal with acceptable heart rate variation;

matching a second string of beats in the second EKG signal with the first string of beats identified in the first EKG signal; and

selecting within the matched string of beats one or more qualified beats, wherein the qualified beats are preceded by QRS-matched beats located in a non-noisy segments of the matched string of beats;

27. The method of claim 26, wherein acceptable heart rate variation is identified as a difference between a maximum heart rate and a minimum heart rate within the first string of beats is less than five beats per minute.

28. The method of claim 26, wherein matching a second string of beats in the second electrocardiogram signal with the first string of beats includes matching heart rate patterns.

29. The method of claim 28, wherein the second string of beats is selected to match the heart rate provided in the first string of beats.

30. The method of claim 25, wherein calculating a QT interval based on the selected qualified beats is defined by the equation:

iQT=(iRpk_a−

iRon_a)+(iToff_b−

iRpk_b), wherein iQT is the QT interval, iRpk_a is the QRS peak of a qualified beat associated with the first EKG signal, iRon_a is the onset of the QRS complex of a qualified beat associated with the first EKG signal, iToff_b is the T-wave offset of a qualified beat associated with the second EKG signal, and iRpk_b is the QRS peak of a qualified beat associated with the second EKG signal.