RMS electrocardiography system and method

• US 8,849,381 B2
• Filed: 07/11/2006
• Issued: 09/30/2014
• Est. Priority Date: 07/11/2006
• Status: Expired due to Fees

• Current Assignee: Covance (Canada), Inc. (Laboratory Corporation Of America Holdings)
• Original Assignee: Covance (Canada), Inc. (Laboratory Corporation Of America Holdings)
• Inventors: Lux, Robert L., Mason, Jay W.
• Primary Examiner(s): Koharski, Christopher D
• Assistant Examiner(s): Dinga, Roland
• Application Number:
  US11/484,539
• Publication Number:
  US 20080015453A1
• Time in Patent Office: 3,003 Days
• Field of Search: 600509-528
• US Class Current: 600/509
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/355 Detecting T-waves
• CPC Class Codes: A61B 5/36 Detecting PQ interval, PR interval or QT interval
• 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

Abstract

A system for assessing a cardiac condition of a subject includes a sensor configured to record a plurality N of electrocardiographic signals from the subject to generate an ECG (electrocardiogram). The system further includes a processor configured to compute an RMS (root-mean-square) magnitude function from the recorded signals, and to measure from the RMS magnitude function an RMS variable that contains information about the cardiac condition of the subject. The ECG may be a standard 12-lead clinical ECG. The measured RMS variables may include RMS T-wave width, RMS RT recovery time, and RMS QT interval.

Claims

1. A system for assessing a cardiac condition of a subject, the system comprising:

electronic circuitry configured to record a plurality N of electrocardiographic signals from the subject to generate an ECG (electrocardiogram); and

a processor configured to compute estimates of a plurality of variables from the recorded signals that contain information about the cardiac condition of the subject using at least one RMS (root-mean-square) magnitude function to compute RMS variables that contain information about the cardiac condition of the subject including fiducial marks providing, on a beat by beat basis, estimates of;

(a) the mean ventricular depolarization time, (b) the mean ventricular repolarization time, (c) the mean ventricular action potential duration, and (d) the ranges of both depolarization and repolarization times;

wherein a mathematical formulation of the RMS magnitude function comprises;

2. The system of claim 1, wherein the system further comprises one or more monitoring electrodes configured to receive the electrocardiographic signals from the subject when placed in contact with the subject.

3. The system of claim 1, wherein at least one of the RMS variables is substantially independent of the subject'"'"'s heart rate.

4. The system of claim 3, wherein the cardiac condition comprises ventricular repolarization of the subject, and wherein the RMS variable comprises an RMS T-wave width of the ECG.

5. The system of claim 4, wherein the processor is further configured to measure the T-wave width from T-wave onset to T-wave offset, and wherein the T-wave width electrocardiographically represents a range of ventricular repolarization times of the subject.

6. The system of claim 1, wherein the cardiac condition comprises average cardiac depolarization and repolarization times of the subject, and wherein the RMS variables comprise:

an estimate AT of mean depolarization time;

an estimate RT of mean repolarization time.

7. The system of claim 6, wherein the processor is configured to measure an RMS RTI recovery time from peak of the RMS QRS complex to peak of the RMS T-wave, and wherein the RMS RTI electrocardiographically represents the average cardiac ventricular action potential duration of the subject.

8. The system of claim 1, wherein the cardiac condition comprises a total duration of ventricular depolarization and repolarization of the subject, and wherein the RMS variable comprises an RMS QT interval of the ECG.

9. The system of claim 8, wherein the processor is configured the RMS QT interval from onset of RMS-QRS to RMS T-wave offset, and wherein the RMS QT interval electrocardiographically represents the total duration of ventricular depolarization and repolarization of the subject.

10. The system of claim 1, wherein the plurality of signals further comprise a Holter data stream.

11. The system of claim 10, wherein the Holter data stream is taken over a time period of between about 24 hours to about 48 hours.

12. The system of claim 1, wherein the electrocardiographic signals represent at least one of:

individual recorded heart beats of the subject;

time-aligned heart beats of the subject; and

signal averaged heart beats of the subject.

13. The system of claim 1, wherein the ECG comprises a body surface electrocardiogram.

14. The system of claim 1, wherein the processor is further configured and arranged to perform a parabolic fit estimate of the RMS magnitude function.

15. The system of claim 14, wherein the parabolic fit estimate is implemented by centering a parabolic segment at each sample of the digital signal, E_RMS(iΔ

t), wherein Δ

t represents the digital sampling interval, and calculating the second derivative function, E″

_RMS(i), for enhancing delineation of inflection points.

16. The system of claim 15, wherein E″

_RMS(i) is calculated in accordance with the following

17. The system of claim 16, wherein the filter width is set to between about 60 milliseconds and about 180 milliseconds.

18. The system of claim 16, wherein the filter width is set to about 60 milliseconds.