QT interval determination methods and related devices

• US 9,986,932 B2
• Filed: 11/17/2014
• Issued: 06/05/2018
• Est. Priority Date: 11/17/2014
• Status: Active Grant

• Current Assignee: Medtronic Monitoring, Inc. (Medtronic Plc)
• Original Assignee: Medtronic Monitoring, Inc. (Medtronic Plc)
• Inventors: Chakravarthy, Niranjan, Chavan, Abhi, Williams, Scott, Gudivada, Rao
• Primary Examiner(s): D ABREU, MICHAEL JOSEPH
• Application Number:
  US14/543,180
• Publication Number:
  US 20160135708A1
• Time in Patent Office: 1,296 Days
• 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 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, and;

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

identifies first QRS complex attributes based only on the first EKG signal, wherein identified first QRS complex attributes include onset of the QRS complex (iRon_a) and QRS complex peak (IRpk_a);

identifies second QRS complex attributes based only on the second EKG signal, wherein identified second QRS complex attributes include QRS complex peak (IRpk_b) and T-wave offset (iToff_b);

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

measures QT intervals within the qualified beat segments based on the identified first and second QRS complex attributes, based on the equation iQT=(iRpk_a−

iRon_a)+(iToff_b-Rpk_b), wherein iQT is the QT interval; and

detecting a long QT interval based on a comparison of the measured QT interval to a threshold value.

2. The monitoring system of claim 1, wherein locating the T-wave offset for each beat includes utilizing and 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.

3. The monitoring system of claim 2, 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.

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

5. The monitoring system of claim 4, wherein the QT interval measurement module provides generated alerts and the received first EKG signal to a remote monitoring center.

6. The monitoring system of claim 1, 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.

7. The monitoring system of claim 6, wherein the first EKG signal and the second EKG signal are aligned based on timestamps associated with both EKG signals.

8. The monitoring system of claim 1, 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.

9. The monitoring system of claim of 8, 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.

10. 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.

11. 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.