QT interval determination methods and related devices

Patent metadata

Field	Value
Publication number	US-10722133-B2
Application number	US-201815975099-A
Country	US
Kind code	B2
Filing date	May 9, 2018
Priority date	Nov 17, 2014
Publication date	Jul 28, 2020
Grant date	Jul 28, 2020

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.

First claim

The invention claimed is:

1. A monitoring system for measuring QT intervals, the monitoring system comprising:
a monitoring device adhered to a patient at a location and configured to monitor an electrocardiogram (EKG) signal associated with the patient; and
a QT interval measurement module configured to:
receive the EKG signal from the monitoring device;
identify QRS complex attributes and heart rate attributes for each beat within the received EKG signal, wherein the QRS complex attributes include a peak of a QRS complex (iRpk) and a QRS onset (iRon);
generate a T-wave offset estimate (iToff_estimate) based at least in part on the identified heart rate attributes;
identify a T-wave offset detection window based on the identified peak of the QRS complex (iRpk) and the generated T-wave offset estimate (iToff_estimate);
locate a T-wave offset (iToff) within the identified T-wave offset detection window based on one or more detected maximums or minimums within the T-wave offset detection window; and
measure a QT interval based on the identified QRS onset (iRon) and the located T-wave offset (iToff).

2. The monitoring system of claim 1 , wherein the QT interval measurement module is further configured to generate an alert in response to detecting a long QT interval.

3. The monitoring system of claim 2 , wherein the QT interval measurement module is further configured to provide the generated alert and the received EKG signal to a remote monitoring center.

4. The monitoring system of claim 1 ,
wherein the QT interval measurement module is further configured to:
identify beats within the received EKG signal as noisy or non-noisy; and
identify a beat segment as non-noisy in response to identifying a consecutive number of beats as non-noisy,

wherein to measure the QT interval, the QT interval measurement module is configured to select only non-noisy beat segments.

5. The monitoring system of claim 1 , wherein the QT interval measurement module is further configured to select a beat segment to measure the QT interval based on one or more of a time of day, an activity level of the patient, an orientation of the patient, or a heart rate of the patient.

6. The monitoring system of claim 1 , wherein the QT interval measurement module is further configured to discards beats in which the QT interval measurement module cannot discern at least one of the QRS onset (iRon) or the T-wave offset (iToff) within the EKG signal even if the beat is non-noisy.

7. The monitoring system of claim 1 , wherein the T-wave offset detection window starts from the generated T-wave offset estimate (iToff_estimate) and extends by a threshold value.

8. The monitoring system of claim 1 , wherein to generate the T-wave offset estimate (iToff_estimate) based at least in part on the identified heart rate attributes, the QT interval measurement module is configured to use the identified heart rate attributes and a look-up table to estimate the T-wave offset detection window.

9. The monitoring system of claim 1 , wherein the QT interval measurement module is located in an intermediate device that comprises:
a processor configured to execute for executing instructions stored in a computer readable medium; and
an antenna configured to receive the EKG signal from the monitoring device.

10. A method for measuring QT intervals, the method comprising:
receiving an electrocardiogram (EKG) signal associated with a patient;
identifying QRS complex attributes and heart rate attributes for each beat within the received EKG signal, wherein the QRS complex attributes include a peak of a QRS complex (iRpk) and a QRS onset (iRon);
generating a T-wave offset estimate (iToff_estimate) based at least in part on the identified heart rate attributes;
identifying a T-wave offset detection window based on the identified peak of the QRS complex (iRpk) and the generated T-wave offset estimate (iToff_estimate);
locating a T-wave offset (iToff) within the identified T-wave offset detection window based on one or more detected maximums or minimums within the T-wave offset detection window; and
measuring a QT interval based on the identified QRS onset (iRon) and the located T-wave offset (iToff).

11. The method of claim 10 , further comprising:
identifying beats within the received EKG signal as noisy or non-noisy; and
setting beat-wise noise flags with respect to those beats identified as noisy.

12. The method of claim 11 , further comprising identifying a qualified beat segment within the EKG signal, wherein the qualified beat segment comprises at least a threshold number of consecutive non-noisy beats.

13. The method of claim 12 , wherein measuring the QT interval comprises measuring the QT measured with respect to only qualified beat segments.

14. The method of claim 10 , further comprising setting a long QT syndrome flag in response to determining that the measured QT interval exceeds a threshold value.

15. The method of claim 10 , further comprising:
storing the QT interval; and
using the QT interval as a benchmark for comparison to subsequently measured QT intervals.

16. A device comprising:
an antenna configured to receive an electrocardiogram (EKG) signal associated with the patient;
a memory operably coupled to a processor; and
the processor, wherein the processor is configured to:
identify QRS complex attributes and heart rate attributes for each beat within the received EKG signal, wherein the QRS complex attributes include a peak of a QRS complex (iRpk) and a QRS onset (iRon);
generate a T-wave offset estimate (iToff_estimate) based at least in part on the identified heart rate attributes;
identify a T-wave offset detection window based on the identified peak of the QRS complex (iRpk) and the generated T-wave offset estimate (iToff_estimate);
locate a T-wave offset (iToff) within the identified T-wave offset detection window based on one or more detected maximums or minimums within the T-wave offset detection window;
measure a QT interval based on the identified QRS onset (iRon) and the located T-wave offset (iToff); and
output an indication of the measured QT interval to a remote monitoring center.

17. The device of claim 16 , wherein the processor is further configured to:
determine that the measured QT interval is a long QT interval; and
generate, in response to determining that the measured QT interval is a long QT interval, an alert.

18. The device of claim 17 , wherein the processor is further configured to output, to the remote monitoring center, the alert and the received EKG signal.

19. The device of claim 16 ,
wherein the processor is further configured to:
identify beats within the received EKG signal as noisy or non-noisy; and
identify a beat segment as non-noisy in response to identifying a consecutive number of beats as non-noisy,

wherein to measure the QT interval, the processor is configured to select only non-noisy beat segments.

20. The device of claim 16 , wherein the T-wave offset detection window starts from the generated T-wave offset estimate (iToff_estimate) and extends by a threshold value.

Assignees

• Medtronic Monitoring Inc

Inventors

• Chakravarthy Niranjan
• Chavan Abhi
• Williams Scott
• Gudivada Rao

Classifications

• A61B5/36 Primary

  Detecting PQ interval, PR interval or QT interval · CPC title

• A61B5/366 Primary

  Detecting abnormal QRS complex, e.g. widening · CPC title

• G16H50/30

  for calculating health indices; for individual health risk assessment · CPC title

• A61B5/349

  Detecting specific parameters of the electrocardiograph cycle · CPC title

• A61B5/316 Primary

  Modalities, i.e. specific diagnostic methods · CPC title