Method and system for providing characterizations of waveform representations of heart function

• US 5,827,196 A
• Filed: 07/15/1997
• Issued: 10/27/1998
• Est. Priority Date: 07/15/1997
• Status: Expired due to Term

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Yeo, Cheuw Lee, Wang, Jyh-yun J.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): SCHAETZLE, KENNEDY
• Application Number:
  US08/893,115
• Time in Patent Office: 469 Days
• Field of Search: 128/901, 600/509, 600/521, 607/27
• US Class Current: 600/509
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

A method and system for providing highly accurate characterizations of waveform representations of heart function, such as QRS complexes, where such waveform representations are derived from electrocardiographic measurements. The method and system accomplish their objects via the following. One or more signals indicative of heart function are measured and sampled. One or more signal quality indexes are calculated for each of the measured and sampled one or more signals. The signal quality indexes are calculated by dividing a maximum sample value for each one or more measured and sampled signal by a calculated divisor. One or more weighting factors, dependent upon the calculated signal quality index of each of the one or more measured and sampled signals are calculated. And, a waveform representation composed of each of the one or more measured and sampled signals indicative of heart function multiplied by its calculated weighting factor is created.

Claims

1. A method for characterizing the quality of signals indicative of heart function, where such signals indicative of heart function are derived from electrocardiographic measurements, said method comprising the steps of:

measuring one or more signals indicative of heart function;

sampling at a cardinal number of points each of said measured one or more signals;

determining, for each of said sampled one or more signals, a maximum sampled value that occurred over said cardinal number of sample points; and

calculating, for each of said sampled one or more signals, a signal quality index by dividing said determined maximum value by a divisor associated with each of said sampled one or more signals.

2. The method of claim 1 wherein said step of calculating a signal quality index further comprises the steps of:

calculating said divisor associated with each of said one or more sampled signals by summing, for each of said sampled one or more signals, each sampled value that was taken at each of said cardinal number of sample points.

3. The method of claim 1 wherein said step of calculating a signal quality index further comprises the steps of:

summing, for each of said sampled one or more signals, each sampled value that was taken at each of said cardinal number of sample points; and

calculating said divisor associated with each of said one or more sampled signals by multiplying the results of said summing step by the reciprocal of the number of cardinal points where said sampling occurred.

4. A method for providing highly accurate characterizations of waveform representations of heart function, where such waveform representations are derived from electrocardiographic measurements, said method comprising the steps of:

measuring one or more signals indicative of heart function;

calculating a signal quality index for each of said measured one or more signals indicative of heart function;

calculating one or more weighting factors dependent upon said calculated signal quality index for each of said one or more measured signals indicative of heart function; and

creating a waveform representation comprised of each of said one or more measured signals indicative of heart function multiplied by said calculated weighting factor corresponding to said each of said one or more measured signals indicative of heart function.

5. The method of claim 4, wherein said step of calculating a signal quality index further comprises the steps of:

measuring one or more signals indicative of heart function;

sampling at a cardinal number of points each of said measured one or more signals;

determining, for each of said sampled one or more signals, a maximum sampled value that occurred over said cardinal number of sample points; and

calculating, for each of said sampled one or more signals, said signal quality index by dividing said determined maximum value by a divisor associated with each of said sampled one or more signals.

6. The method of claim 5 wherein said step of calculating said signal quality index further comprises the steps of:

calculating said divisor associated with each of said one or more sampled signals by summing, for each of said sampled one or more signals, each sampled value that was taken at each of said cardinal number of sample points.

7. The method of claim 5 wherein said step of calculating said signal quality index further comprises the steps of:

summing, for each of said sampled one or more signals, each sampled value that was taken at each of said cardinal number of sample points; and

calculating said divisor associated with each of said one or more sampled signals by multiplying the results of said summing step by the reciprocal of the number of cardinal points where said sampling occurred.

8. The method of claim 4 wherein said step of calculating one or more weighting factors further comprises the steps of:

summing said calculated signal quality index for each of said one or more measured signals indicative of heart function;

comparing said sum of said calculated signal quality index for each of said one or more measure signals to zero;

in response to said comparing step indicating that said sum of said calculated signal quality indexes is equal to zero, calculating said one or more weighting factors to all be equal to the number one divided by the total aggregate number of said measured one or more signals; and

in response to said comparing step indicating that said sum of said calculated signal quality index for each of said one or more signals is not equal to zero, calculating said one or more weighting factors for each of said one or more measured signals by dividing said signal quality index for each of said one or more signals by the result of said summing step.

9. The method of claim 4 wherein said step of calculating one or more weighting factors further comprises the steps of:

adjusting said calculated signal quality indexes in special case instances;

summing said calculated signal quality index for each of said one or more measured signals indicative of heart function;

comparing said sum of said calculated signal quality index for each of said one or more measure signals to zero;

in response to said comparing step indicating that said sum of said calculated signal quality indexes is equal to zero, calculating said one or more weighting factors to all be equal to the number one divided by the total aggregate number of said measured one or more signals; and

in response to said comparing step indicating that said sum of said calculated signal quality index for each of said one or more signals is not equal to zero, calculating said one or more weighting factors for each of said one or more measured signals by dividing said signal quality index for each of said one or more signals by the result of said summing step.

10. The method of claim 9 wherein said step of adjusting said calculated signal quality indexes in special case instances further comprises the steps of:

sampling at a cardinal number of points each of said measured one or more signals;

determining a maximum sampled value of each of said measured one or more signals that occurred over said cardinal number of sample points;

comparing said determined maximum sampled value of each of said measured one or more signals to a prespecified threshold; and

in response to such comparing step showing that all of said determined maximum sampled values are less than or equal to said prespecified threshold, calculating said signal quality index for each of said measured one or more signals to be equal to zero.

11. The method of claim 9 wherein said step of adjusting said calculated signal quality indexes in special case instances further comprises the steps of:

comparing said calculated signal quality index for each of said measured one or more signals to a first prespecified threshold; and

in response to said comparing step showing that at least one of said calculated signal quality index for each of said measured one or more signals was above said first prespecified threshold;

setting equal to zero the signal quality index for each of said one or more measured signals whose determined maximum value was less than or equal to a second prespecified threshold provided that said each of said one of or more measured signals was not previously found to be the maximum signal quality index; and

utilizing said calculated signal quality index for each of said measured one or more signals for each of said measured one or more signals whose signal quality index has not previously been set equal to zero.

12. The method of claim 9 wherein said step of adjusting said calculated signal quality indexes in special case instances further comprises the steps of:

maintaining a running average of high frequency noise within each one of said measured one or more signals;

maintaining a running average of low frequency noise within each one of said measured one or more signals;

comparing said maintained running average of high frequency noise within each of said measured one or more signals to a first calculated threshold;

comparing said maintained running average of low frequency noise within each of said measured one or more signals to a second calculated threshold; and

setting equal to zero the calculated signal quality index for any of said measured one or more signals where said comparing steps demonstrated for said any of said measured one or more signals either that said maintained running average of low frequency noise exceeded said first computed threshold or that said maintained running average of high frequency noise exceeded said second computed threshold.

13. A system for characterizing the quality of signals indicative of heart function, where such signals indicative of heart function are derived from electrocardiographic measurements, said system comprising:

means for measuring one or more signals indicative of heart function;

means for sampling at a cardinal number of points each of said measured one or more signals;

means for determining, for each of said sampled one or more signals, a maximum sampled value that occurred over said cardinal number of sample points; and

means for calculating, for each of said sampled one or more signals, a signal quality index by dividing said determined maximum value by a divisor associated with each of said sampled one or more signals.

14. The system of claim 13 wherein said means for calculating a signal quality index further comprises:

means for calculating said divisor associated with each of said one or more sampled signals by summing, for each of said sampled one or more signals, each sampled value that was taken at each of said cardinal number of sample points.

15. The system of claim 13 wherein said means for calculating a signal quality index further comprises:

means for summing, for each of said sampled one or more signals, each sampled value that was taken at each of said cardinal number of sample points; and

means for calculating said divisor associated with each of said one or more sampled signals by multiplying the results of said summing step by the reciprocal of the number of cardinal points where said sampling occurred.

16. A system for providing highly accurate characterizations of waveform representations of heart function, where such waveform representations are derived from electrocardiographic measurements, said system comprising:

means for measuring one or more signals indicative of heart function;

means for calculating a signal quality index for each of said measured one or more signals indicative of heart function;

means for calculating one or more weighting factors dependent upon said calculated signal quality index for each of said one or more measured signals indicative of heart function; and

means for creating a waveform representation comprised of each of said one or more measured signals indicative of heart function multiplied by said calculated weighting factor corresponding to said each of said one or more measured signals indicative of heart function.

17. The system of claim 16, wherein said means for calculating a signal quality index further comprises:

means for measuring one or more signals indicative of heart function;

means for sampling at a cardinal number of points each of said measured one or more signals;

means for determining, for each of said sampled one or more signals, a maximum sampled value that occurred over said cardinal number of sample points; and

means for calculating, for each of said sampled one or more signals, said signal quality index by dividing said determined maximum value by a divisor associated with each of said sampled one or more signals.

18. The system of claim 17 wherein said means for calculating said signal quality index further comprises:

means for calculating said divisor associated with each of said one or more sampled signals by summing, for each of said sampled one or more signals, each sampled value that was taken at each of said cardinal number of sample points.

19. The system of claim 16 wherein said means for calculating said signal quality index further comprises:

means for summing, for each of said sampled one or more signals, each sampled value that was taken at each of said cardinal number of sample points; and

means for calculating said divisor associated with each of said one or more sampled signals by multiplying the results of said summing step by the reciprocal of the number of cardinal points where said sampling occurred.

20. The system of claim 16 wherein said means for calculating one or more weighting factors further comprises:

means for summing said calculated signal quality index for each of said one or more measured signals indicative of heart function;

means for comparing said sum of said calculated signal quality index for each of said one or more measure signals to zero;

means, responsive to said means for comparing indicating that said sum of said calculated signal quality indexes is equal to zero, for calculating said one or more weighting factors to all be equal to the number one divided by the total aggregate number of said measured one or more signals; and

means, responsive to said means for comparing indicating that said sum of said calculated signal quality index for each of said one or more signals is not equal to zero, for calculating said one or more weighting factors for each of said one or more measured signals by dividing said signal quality index for each of said one or more signals by the resultant of said means for summing.

21. The system of claim 16 wherein said means for calculating one or more weighting factors further comprises:

means for adjusting said calculated signal quality indexes in special case instances;

means for summing said calculated signal quality index for each of said one or more measured signals indicative of heart function;

means for comparing said sum of said calculated signal quality index for each of said one or more measure signals to zero;

means, responsive to said means for comparing indicating that said sum of said calculated signal quality indexes is equal to zero, for calculating said one or more weighting factors to all be equal to the number one divided by the total aggregate number of said measured one or more signals; and

means, responsive to said means for comparing indicating that said sum of said calculated signal quality index for each of said one or more signals is not equal to zero, for calculating said one or more weighting factors for each of said one or more measured signals by dividing said signal quality index for each of said one or more signals by the resultant of said means for summing.

22. The system of claim 21 wherein said means for adjusting said calculated signal quality indexes in special case instances further comprises:

means for sampling at a cardinal number of points each of said measured one or more signals;

means for determining a maximum sampled value of each of said measured one or more signals that occurred over said cardinal number of sample points;

means for comparing said determined maximum sampled value of each of said measured one or more signals to a prespecified threshold; and

means, responsive to such means for comparing showing that all of said determined maximum sampled values are less than or equal to said prespecified threshold, for calculating said signal quality index for each of said measured one or more signals to be equal to zero.

23. The system of claim 21 wherein said means for adjusting said calculated signal quality indexes in special case instances further comprises:

means for comparing said calculated signal quality index for each of said measured one or more signals to a first prespecified threshold; and

means, responsive to said means for comparing showing that at least one of said calculated signal quality index for each of said measured one or more signals was above said first prespecified threshold;

for setting equal to zero the signal quality index for each of said one or more measured signals whose determined maximum value was less than or equal to a second prespecified threshold provided that said each of said one of or more measured signals was not previously found to be the maximum signal quality index; and

for utilizing said calculated signal quality index for each of said measured one or more signals for each of said measured one or more signals whose signal quality index has not previously been set equal to zero.

24. The system of claim 21 wherein said means for adjusting said calculated signal quality indexes in special case instances further comprises:

means for maintaining a running average of high frequency noise within each one of said measured one or more signals;

means for maintaining a running average of low frequency noise within each one of said measured one or more signals;

means for comparing said maintained running average of high frequency noise within each of said measured one or more signals to a first calculated threshold;

means for comparing said maintained running average of low frequency noise within each of said measured one or more signals to a second calculated threshold; and

means for setting equal to zero the calculated signal quality index for any of said measured one or more signals where said comparing steps demonstrated for said any of said measured one or more signals either that said maintained running average of low frequency noise exceeded said first computed threshold or that said maintained running average of high frequency noise exceeded said second computed threshold.