US3868567A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Measurement of ST depression of electrocardiograms
Assignee: University of Washington
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Filing: 1973-11-26
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Granted: 1975-02-25
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Expires: 1993-11-26
Abstract
Abstract A method and apparatus for electronically determining the ST depression of an electrocardiogram waveform relative to the PQ level of the same waveform is disclosed. The analyzer and the associated method employ delta modulation and demodulation for processing information. By varying a weight signal in the delta demodulator in a predetermined manner, the average ST depression is obtained directly without the necessity of comparing a delayed version of the EKG with an undelayed version of the EKG to overlap the ST and PQ segments of interest. The method and apparatus disclosed can be used to determine the average difference between two segments of waveforms other than an electrocardiogram by adjusting the weight signal.
Inventors
- 👤 Philip A Ekstrom
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:11
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/24; A61B5/316; A61B5/318; A61B5/346; A61B5/349; A61B5/358; G; G01; G01R; G01R23/00; G01R23/02
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
78 words
A method for determining the average ST segment depression of an electrocardiogram (EKG) waveform relative to the PQ segment of the same EKG waveform comprising the steps of: a. delta modulating said EKG waveform to produce a digital representation thereof; b. delaying said digital representation; c. delta demodulating the digital representation to directly yield said average ST depression; said delay being sufficient to allow the R portion of said EKG waveform to initiate operation of said demodulating step.
Claim 2
Independent Claim
78 words
A method for determining the average ST segment depression of an electrocardiogram (EKG) waveform relative to the PQ segment of the same EKG waveform comprising the steps of: a. delta modulating said EKG waveform to produce a digital representation thereof; b. delaying said digital representation; c. delta demodulating the digital representation to directly yield said average ST depression; said delay being sufficient to allow the R portion of said EKG waveform to initiate operation of said demodulating step.
Claim 3
Dependent Claim
36 words
A method in accordance with claim 1 including the additional steps of: a. sampling a plurality of said average ST depressions corresponding to a plurality of EKG waveforms, b. displaying the average value of the samples.
Claim 4
Dependent Claim
37 words
A method in accordance with claim 1 further including the step of: a. adding a high frequency dither signal to the EKG waveform prior to delta modulating it to improve the amplitude resolution of the delta modulation.
Claim 5
Dependent Claim
52 words
A method in accordance with claim 1 wherein said step of delta modulating includes the substeps of: a. comparing the instantaneous value of said EKG waveform with a stored voltage level to produce a difference output, and b. adjusting said stored voltage level in accordance with the difference output of said comparison.
Claim 6
Dependent Claim
17 words
The method of claim 1 wherein said delaying step provides a fixed delay for the digital representation.
Claim 7
Dependent Claim
97 words
The method in accordance with claim 1 wherein the step of demodulating includes the substeps of: generating a weight signal whose amplitude varies such that it linearly increases from an initial value to a maximum value during the digital representation of the PQ segment, remains constant at said maximum value during the period between the digital representation of the PQ and ST segments, and linearly decreases from said maximum value to said initial value during the digital representation of the ST segment; and utilizing the delayed digital representation to gate said weight signal into an accumulating memory.
Claim 8
Dependent Claim
34 words
The method in accordance with claim 6 wherein the said weight signal is added to or substracted from said memory according to the polarity of each digital bit of the digital representation gating it.
Claim 9
Dependent Claim
84 words
An EKG analyzer for determining the average ST segment depression of an electrocardiogram (EKG) waveform relative to the PQ segment of the same EKG waveform comprising: a. modulator means for delta modulating said EKG to produce a digital representation thereof, b. delay means for delaying said digital representation, c. demodulator means for delta demodulating said digital representation to directly yield said average ST depression; said delay being sufficient to allow the R portion of said EKG waveform to initiate operation of said demodulating means.
Claim 10
Dependent Claim
84 words
An EKG analyzer for determining the average ST segment depression of an electrocardiogram (EKG) waveform relative to the PQ segment of the same EKG waveform comprising: a. modulator means for delta modulating said EKG to produce a digital representation thereof, b. delay means for delaying said digital representation, c. demodulator means for delta demodulating said digital representation to directly yield said average ST depression; said delay being sufficient to allow the R portion of said EKG waveform to initiate operation of said demodulating means.
Claim 11
Dependent Claim
34 words
The analyzer of claim 8 further including: sampling means for sampling a plurality of said average ST depressions corresponding to a plurality of EKGs, and means for displaying the average value of the samples.
Claim 12
Dependent Claim
32 words
The analyzer of claim 8 further including dither means for adding a dither signal to said EKG waveform prior to modulating it to improve the amplitude resolution of said delta modulation means.
Claim 13
Dependent Claim
52 words
The analyzer according to claim 8 wherein said delta modulation means includes: a. comparator meaNs for repetitively comparing the instantaneous value of said EKG waveform with a stored reference voltage to produce a difference output, and b. means for adjusting said reference voltage after each comparison in accordance with said difference output.
Claim 14
Dependent Claim
16 words
The analyzer according to claim 8 wherein said delay means is a fixed length shift register.
Claim 15
Dependent Claim
36 words
The analyzer of claim 8 wherein said demodulation means includes: a. an accumulating memory, b. weight signal generator means for generating a varying weight signal, and c. means for applying said weight signal to said memory.
Claim 16
Dependent Claim
33 words
The analyzer according to claim 13 further including means for zeroing said memory prior to each EKG waveform and wherein said means for applying said weight signal are gated by said digital representation.
Claim 17
Dependent Claim
64 words
The analyzer according to claim 14 wherein said means for applying said weight signal are a pair of switches, one of said pair being operated if a digital bit is 1 causing said weight signal to be added to said memory; the other of said pair being operated if a digital bit is 0 causing said weight signal to be subtracted from said memory.
Claim 18
Dependent Claim
30 words
The analyzer according to claim 14 wherein said weight signal is added to or subtracted from said memory according to the polarity of each digital bit of said digital representation.
Claim 19
Dependent Claim
71 words
The analyzer according to claim 13 wherein said weight signal generating means produces a weight signal whose amplitude linearly increases from an initial value to a maximum value during the digital representation of the PQ segment, remains constant at said maximum value between the digital representation of the PQ and ST segments, and linearly decreases from said maximum value to said initial value during the digital representation of the ST segment.
Claim 20
Dependent Claim
52 words
The analyzer according to claim 17 wherein said weight signal generator means includes: linear integrator means for integrating D.C. signals, switching means for connecting the input of said integrating means to D.C. voltage sources of opposite polarity, and sequential circuit means for operating said switching means to produce said weight signal output.
Claim 21
Dependent Claim
33 words
The analyzer according to claim 18 wherein said weight signal generator means further includes comparator means for detecting the output of said integrator means to control the sequencing of said sequential circuit means.
Claim 22
Dependent Claim
38 words
The analyzer according to claim 18 wherein said weight signal generator means further includes: means for resetting itself and said delta demodulation means, and means for gating said sampling means when said accumulating memory contains said ST depression.
References Cited (Backward Citations)
US3267933A
Cited
US3267934A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-02-24 | 1978-08-26 | 1979-02-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-02-24 | 1982-08-26 | 1983-02-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-02-24 | 1986-08-26 | 1987-02-25 | $7700.00 | Window Closed / Lapsed |