RMS electrocardiography system and method

• US 20080015453A1
• Filed: 07/11/2006
• Published: 01/17/2008
• Est. Priority Date: 07/11/2006
• Status: Active Grant

• Current Assignee: Covance (Canada), Inc. (Laboratory Corporation Of America Holdings)
• Original Assignee: Covance Cardiac Safety Services, Inc. (Laboratory Corporation Of America Holdings)
• Inventors: Mason, Jay W., Lux, Robert L.
• Granted Patent: US 8,849,381 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61B 5/25 Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• 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), the plurality N of signals including at least one of a standard clinical ECG recorded with 12 leads, and a Holter data stream; and

a processor configured to compute an RMS (root-mean-square) magnitude function from the recorded signals, and to measure from the RMS magnitude function one or more RMS variables that contain information about the cardiac condition of the subject.

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 the ECG comprises a standard 12-lead clinical ECG.

4. The system of claim 1,

wherein at least one of the RMS variables is substantially independent of the subject'"'"'s heart rate.

5. The system of claim 4,

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

6. The system of claim 5,

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.

7. 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.

8. The system of claim 7, 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.

9. 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.

10. The system of claim 9,

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.

11. The system of claim 1, wherein a mathematical formulation of the RMS magnitude function comprises:

$E_{R<br><br><br><br>\mathrm{MS}}<br><br>\left(t\right)=\sqrt{\frac{1}{N}<br><br>\sum <br><br>e_i^2<br><br>\left(t\right)}$

where

E_RMS(t) represents the RMS magnitude function at a time t; and

e_i(t) represents the i-th electrocardiographic signal recorded at the time t.

12. The system of claim 1,

wherein the plurality of signals comprise a Holter data stream.

13. The system of claim 12, wherein the Holter data stream is taken over a time period of between about 24 hours to about 48 hours.

14. 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.

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

16. The system of claim 1, wherein N varies from about 2 to about 500.

17. A method of assessing cardiac condition of a subject, the method comprising:

recording a plurality of electrocardiographic signals of the subject;

deriving an RMS (root-mean-square) magnitude function from the plurality of recorded signals; and

measuring from the RMS magnitude function an RMS variable that contains information about the cardiac condition;

wherein the plurality of recorded signals comprise at least one of;

a standard clinical ECG recorded with 12 leads; and

a Holter data stream.

18. The method of claim 17,

wherein the RMS variable is substantially independent of the subject'"'"'s heart rate;

and

wherein the RMS variable comprises an RMS T-wave width of the ECG.

19. The method of claim 17, wherein the cardiac condition comprises at least one of:

ventricular repolarization of the subject;

an average cardiac repolarization time of the subject, and

a duration of ventricular action potential of the subject.

20. The method of claim 17, wherein the RMS variable comprises at least one of:

an RMS RT recovery time of the ECG; and

an RMS QT interval of the ECG.

21. The method of claim 17, wherein a mathematical formulation of the RMS magnitude function comprises:

$E_{R<br><br><br><br>\mathrm{MS}}<br><br>\left(t\right)=\sqrt{\frac{1}{N}<br><br>\sum <br><br>e_i^2<br><br>\left(t\right)}$

where

E_RMS(t) represents the RMS magnitude function at a time t; and

e_i(t) represents the i-th electrocardiographic signal recorded at the time t.

22. A system for evaluating ventricular repolarization of a subject, the system comprising:

a plurality of electrodes configured to record electrocardiographic signals of the subject to generate a standard clinical ECG of the subject; and

a processor configured to compute an RMS (root-mean-square) magnitude function from the plurality of recorded signals, and to measure from the RMS magnitude function an RMS T-wave width of the ECG.