EP0155670A2
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Method and apparatus for analyzing electrocardiographic signals
Assignee: University of Washington
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Filing: 1985-03-19
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Granted: —
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Expires: 2005-03-19
Abstract
Abstract ECG signals are digitized and a template representative of an arrhythmia free interval for a particular patient is formed. Subsequent ECG signals which match the template are averaged to form averaged ECG signals to reduce noise. A fast Fourier transform (FFT) is performed on the terminal 40 millisecond portion of the QRS complex and the ST segment. The 60 db area and 40 Hz intercept of the resultant spectral output are used as a figure of merit in predicting the liklihood of a particular patient experiencing ventricular tachycardia. Alternatively, the FFT magnitude is squared to form energy spectra of the ECG signals and a measure of the energy in a first preselected portion such as the 20 - 50 Hz region is compared with a second preselected portion such as the entire spectra to form a figure of merit for predicting ventricular tachycardia.
Inventors
- 👤 Hans D. Ambos
- 👤 Michael E. Cain
- 👤 Burton E. Sobel
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 16:12
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/24; A61B5/316; A61B5/318; A61B5/346; A61B5/349; A61B5/35; A61B5/72; A61B5/7235; A61B5/7253; A61B5/7257
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
106 words
A method for analyzing electrocardiogram (ECG) signals to determine the presence or absense of a predetermined frequency content in a preselected portion of said ECG signals comprising the steps of: converting analog ECG signals to digital ECG signals; performing a fast Fourier transform (FFT) on said preselected portion of said digital ECG signals; and determining a figure of merit (FOM) associated with the frequency content of said at least a preselected portion of said ECG signals from said output of said Fourier transform step, whereby said determination of the presence or absence of said predetermined frequency content can be determined from the vaule of said FOM.
Claim 2
Independent Claim
106 words
A method for analyzing electrocardiogram (ECG) signals to determine the presence or absense of a predetermined frequency content in a preselected portion of said ECG signals comprising the steps of: converting analog ECG signals to digital ECG signals; performing a fast Fourier transform (FFT) on said preselected portion of said digital ECG signals; and determining a figure of merit (FOM) associated with the frequency content of said at least a preselected portion of said ECG signals from said output of said Fourier transform step, whereby said determination of the presence or absence of said predetermined frequency content can be determined from the vaule of said FOM.
Claim 3
Dependent Claim
26 words
The method of Claim 1 wherein said method further comprises the step of: comparing said FOM with a predetermined FOM associated with said predetermined frequency content.
Claim 4
Independent Claim
43 words
The method of Claim lor 2 wherein said method further comprises the step of: forming an averaged ECG signal by averaging preselected ones of said digital ECG signals before performing a FFT on at least a portion of said averaged EC G signal.
Claim 5
Dependent Claim
107 words
The method of Claim 3 wherein said ECG signals comprises X, Y, and Z signals and said method further comprises: forming an averaged ECG signal for each of said X, Y, and Z signals: forming an ECG template; screening said digital ECG signals through said template to obtain said preselected ones, said step of forming a template further comprising: selecting model X, Y, and Z signals; determining the R-R interval of a selected one of said model X, Y, and Z signals; determining the fiducial point of said selected one; determining the peak to peak amplitude of each of said model X, Y and Z QRS signals.
Claim 6
Dependent Claim
126 words
The method of Claim 4 wherein said step of screening said ECG signals comprises the steps of: choosing candidate X, Y, and Z ECG signals for comparison with said template; performing a multi-point cross correlation between said selected one of said model X, Y, and Z QRS signals and the corresponding one of said candidate X, Y, and Z QRS signals; selecting said candidate ECG signals as a portion of said preselected ones if said R-R interval of said selected one of said candidate QRS signal is within ±20% of said template value; said cross correlation coefficient is greater than or equal to 98%; and at least two out of three of the candidate QRS peak to peak amplitudes are the same as the template values.
Claim 7
Dependent Claim
49 words
The method of Claim 5 wherein said screening step further comprises selecting said candidate ECG signals as a portion of said preselected ones if and only if the X, Y, and Z ECG signals before and after said chosen ECG signal are also acceptable when compared with said template.
Claim 8
Independent Claim
22 words
The method of any of Claims 1 to 6 wherein said preselected portion comprises the terminal 40 milliseconds of the QRS complex.
Claim 9
Independent Claim
21 words
The method of any of Claims 1 to 6 wherein said preselected portion comprises the ST portion of the ECG signal.
Claim 10
Independent Claim
45 words
The method of any of Claims 2 to 8 wherein said step of determining the figure of merit comprises the steps of: . determining the normalized power level of the FFT output at 40 Hz; and determining the 60 dB area of the FFT output.
Claim 11
Dependent Claim
26 words
The method of Claim 9 wherein said method further comprises the step of forming a spectral plot of the FFT output before determining said FOM therefrom.
Claim 12
Dependent Claim
61 words
The method of Claim 9 or 10 wherein said ECG signals comprises X, Y and Z ECG signals and said step of determining said FOM further comprises: determining said FOM for each of said X, Y, and Z ECG signals; and forming the mean of said 40 Hz intercepts and said 60 dB areas from said X, Y, and Z FOM's.
Claim 13
Independent Claim
54 words
The method of any of Claims 9 to 11 wherein said preselected portion of said digital ECG signals comprises the terminal portion of said QRS complex and said figure of merit associated with said predetermined frequency content comprises a 60 dB area greater than 2400 and a 40 Hz drop less than 47 dB.
Claim 14
Independent Claim
49 words
The method of any of Claims 9 to 11 wherein said preselected portion of said digital ECG signals comprises the ST portion and said figure of merit associated with said predetermined frequency content comprises a 60 dB area greater than 2500 and 40 Hz drop less than 52 dB.
Claim 15
Independent Claim
82 words
An apparatus for analyzing electrocardiogram (ECG) signals to determine the presence of a predetermined frequency content in the ECG signal comprising: A/D means for converting analog ECG signals to digital ECG signals; FFT means for performing a fast Fourier transform (FFT) on at least a portion of said digital ECG signals; and FOM means for determining a figure of merit (FOM) for said FFT, said FOM associated with the frequency content of said at least a portion of said digital ECG signals.
Claim 16
Independent Claim
82 words
An apparatus for analyzing electrocardiogram (ECG) signals to determine the presence of a predetermined frequency content in the ECG signal comprising: A/D means for converting analog ECG signals to digital ECG signals; FFT means for performing a fast Fourier transform (FFT) on at least a portion of said digital ECG signals; and FOM means for determining a figure of merit (FOM) for said FFT, said FOM associated with the frequency content of said at least a portion of said digital ECG signals.
Claim 17
Dependent Claim
26 words
The apparatus of Claim 14 wherein said apparatus further comprises comparison means for comparing said FOM with a predetermined FOM associated with said predetermined frequency content.
Claim 18
Independent Claim
122 words
An apparatus for analyzing X, Y, and Z electrocardiagram (ECG) signals to determine the presence of a predetermined frequncy content thereof comprising: A/D means for converting analog X, Y, and Z ECG signals to digital ones; averaging means for averaging selected ones of each of said X, Y, and Z signals for forming averaged X, Y, and Z signals; FFT means for performing a fast Fourier transform (FFT) on at least a portion of each of said averaged X, Y, and Z signals; FOM means for determing a figure of merit (FOM) from the FFT of each of said averaged X, Y, and Z signals; and comparison means for comparing said FOM with a predetermined FOM associated with said predetermined frequency content.
Claim 19
Independent Claim
122 words
An apparatus for analyzing X, Y, and Z electrocardiagram (ECG) signals to determine the presence of a predetermined frequncy content thereof comprising: A/D means for converting analog X, Y, and Z ECG signals to digital ones; averaging means for averaging selected ones of each of said X, Y, and Z signals for forming averaged X, Y, and Z signals; FFT means for performing a fast Fourier transform (FFT) on at least a portion of each of said averaged X, Y, and Z signals; FOM means for determing a figure of merit (FOM) from the FFT of each of said averaged X, Y, and Z signals; and comparison means for comparing said FOM with a predetermined FOM associated with said predetermined frequency content.
Claim 20
Dependent Claim
45 words
The apparatus of Claim 16 wherein said apparatus further comprises: means for selecting said selected ones of said X, Y, and Z signals for averaging comprising means for comparing said ECG X, Y, and Z signals with a predetermined template of a model ECG signal.
Claim 21
Independent Claim
33 words
The apparatus of any of Claims 15 to 17 wherein said at least a portion of said digital ECG signals comprises the terminal 40 milliseconds of a QRS complex of said ECG signals.
Claim 22
Independent Claim
28 words
The apparatus of any of Claims 15 to 17 wherein said at least a portion of said digital ECG signals comprises the ST segment of said ECG signal.
Claim 23
Dependent Claim
28 words
- 20. The apparatus of Claim 18 wherein said predetermined FOM comprises a 60 DB area greater than 2400 and a 40 Hz intercept less than 47 dB.
Claim 24
Dependent Claim
26 words
The apparatus of Claim 19 wherein said predetermined FOM comprises a 60 dB area greater than 2500 and a 40 Hz intercept less than 52 dB.
Claim 25
Independent Claim
91 words
A method for analyzing electrocardiogram (ECG) signals to determine the presence or absence of a predetermined frequency content in a preselected portion of said ECG signals comprising the steps of: converting analog ECG signals to digital ECG signals; forming energy spectra of said preselected portion of said ECG signals; and comparing a measure of the energy content of a first preselected portion of said each of energy spectra with a measure of the energy of a second preselected portion whereby the presence or absence of a predetermined frequency content is determined.
Claim 26
Independent Claim
91 words
A method for analyzing electrocardiogram (ECG) signals to determine the presence or absence of a predetermined frequency content in a preselected portion of said ECG signals comprising the steps of: converting analog ECG signals to digital ECG signals; forming energy spectra of said preselected portion of said ECG signals; and comparing a measure of the energy content of a first preselected portion of said each of energy spectra with a measure of the energy of a second preselected portion whereby the presence or absence of a predetermined frequency content is determined.
Claim 27
Dependent Claim
39 words
The method of Claim 22 wherein the step of forming the energy spectra comprises the steps of: performing a fast-Fourier transform (FFT) on said ECG preselected portion; and squaring the magnitude of said FFT of said ECG preselected portion.
Claim 28
Dependent Claim
27 words
The method of Claim 23 wherein said ECG preselected portion comprises a terminal portion of the QRS portion along with the ST portion of said ECG signals.
Claim 29
Dependent Claim
46 words
The method of Claim 24 wherein the step of comparing an energy measure of the energy content comprises the step of: comparing the maximum amplitude of each frequency peak in said first preselected portion with the maximum amplitude of the largest peak in said energy spectra.
Claim 30
Dependent Claim
45 words
The method of Claim 24 wherein the step of comparing an energy measure of the energy content comprises the step of comparing the area of the energy spectra in said first preselected portion with the area of the energy spectra in said second preselected portion.
Claim 31
Dependent Claim
23 words
The method of Claim 25 wherein said first preselected portion comprises approximately the region from 20 Hz to between 50 and 70 Hz.
Claim 32
Independent Claim
36 words
The method of any of Claims 24 to 26 wherein said first preselected portion comprises approximately the region from at least 20 Hz to 50 Hz and said second preselected portion comprises approximately the entire spectra.
References Cited (Backward Citations)
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