US 3,940,692 A · Apparatus for monitoring recurrent waveforms

Abstract

A method and apparatus for monitoring recurrent waveforms such as electrocardiogram (e.c.g.) waveforms. The e.c.g. apparatus comprises integrators and stores for storing integrated segments of a normal, reference waveform complex. A timing circuit derives timing signals from the e.c.g. waveform to be monitored. The timing signals represent the time location of particular selected parts of the waveform which are to be compared with the corresponding parts of the stored waveform. The e.c.g. waveform is corrected by subtracting a version of the waveform after it has passed through a low pass filter from a delayed version. Corrected segments of the waveform are integrated and subtracted from the corresponding stored segments of the reference waveform to provide a difference signal and the difference signals are quantitatively summed. An output signal is produced if the total sum of the magnitudes of the difference signals exceeds a predetermined value to indicate an abnormal complex.

Claims33

Dependent claims

A method of monitoring a recurrent waveform to detect abnormal waveform complexes comprising the steps of integrating successive segments of a waveform complex, determining the difference between the integrated value of each segment in the complex and the integrated values of corresponding segments of (p + 1) different normal waveform complexes, where p is an integer, to provide (p + 1) sets of difference signals, quantitatively summing the difference signals associated with each normal waveform and producing a signal and/or record to indicate an abnormal complex if the total sum of the magnitudes of the difference signals associated with a first normal waveform complex exceeds a first threshold level and the sums of the magnitudes of the p other difference signals are not less than a second threshold level for each of the p other normal waveform complexes.

A method of monitoring a recurrent waveform to detect abnormal waveform complexes comprising the steps of integrating and storing segments of a normal waveform complex to be used as a reference, integrating successive segments of a waveform complex, deriving timing signals from the recurrent waveform wherein the timing signals represent the time location of particular selected parts of the waveform complex required to be compared with the integrated value of corresponding parts of the stored normal complex, deriving a correcting signal by filtering the waveform to be monitored by passing it through a low-pass filter to provide a baseline signal, delaying the waveform, subtracting said correcting signal from said delayed waveform to provide a corrected waveform, determining, with the aid of the timing signals, the difference between the integrated value of each segment in the corrected complex and the integrated value of a corresponding segment of the normal waveform complex to provide a difference signal, quantitatively summing the difference signals and producing a signal and/or record if the total sum of the magnitudes of the difference signals exceed a predetermined value to indicate an abnormal complex.

Apparatus for monitoring a recurrent waveform to detect abnormal waveform complexes comprising means for integrating and storing segments of a normal waveform complex to be used as a reference, means for integrating successive segments of a waveform complex to be monitored, means for timing signals from the recurrent waveform wherein the timing signals represent the time location of particular selected parts of the waveform complex required to be compared with the integrated value of corresponding parts of the stored normal complex, means for deriving a correcting signal, including means for filtering the waveform to be monitored by passing it through a low-pass filter to provide a baseline signal, means for delaying the waveform, means for subtracting said correcting signal from said delayed waveform to provide a correct waveform, means for determining, with the aid of the timing signals, the difference between the integrated value of each segment in the corrected complex and the integrated value of a corresponding segment of the normal waveform complex to provide a difference signal, means for quantitatively summing the difference signals and for producing a signal and/or record if the total sum of the magnitudes of the difference signals exceed a predetermined value to indicate an abnormal complex.

Apparatus for monitoring a series of incoming waveform complexes, normally having a predominant peaked portion, to detect abnormal complexes, comprising:

delay means for delaying an incoming waveform complex;
trigger means including
i. a first trigger path receiving said incoming complex and comprising a high pass filter, a low pass filter, a full wave rectifier, a low pass filter and a first derivative circuit,
ii. a second trigger path serially following said first path and comprising means providing a second derivative signal, a comparator actuable when said second derivative signal exceeds a high frequency noise threshold and an AND-gate in series, said second derivative signal causing a peak signal, at the peak of said peaked portion, through a peak rectifier,
iii. a third trigger path paralleling said second path and comprising means comparing the second differential signal to a reference level monostable means triggered thereby at the zero crossing of the second derivative signal, and said AND-gate, said AND-gate being responsive to coincidence of outputs from said second and third paths for producing a trigger signal time related to the center of each incoming complex's peaked portion which significantly exceeds the high frequency noise level in such complex;
and
inhibit means including
i. low pass filter means responsive to said incoming complex for providing a baseline signal,
ii. first derivative and rectifier means responsive to said baseline signal for providing a baseline slope signal,
iii. rectifier and comparator means providing a signal when said baseline signal exceeds a threshold level,
iv. means responsive to a selected fraction of the total area of one stored normal complex exceeding the baseline slope signal for also providing a signal,
v. means also providing a signal when the mean high frequency noise level of the incoming complex exceeds a preselected fraction of said peak signal,
vi. stretch circuit means responsive to a said signal from (iii), (iv) or (v) above for providing an inhibit signal,
vii. a series path including a notch filter means, high pass filter, rectifier, low pass filter and peak rectifier for signaling said mean high frequency noise level and means applying a corresponding signal to (v) above and to said second trigger path comparator.

11 more elements

Dependencies are inferred from the claim text.

Apparatus for monitoring recurrent waveforms

Life of this patent

Apparatus for monitoring recurrent waveforms

Life of this patent

Abstract

Claims33