JPH06327641A - Detector for high frequency miniature potential - Google Patents

Abstract

PURPOSE:To provide a system being possible to make a precise detection of the rate potential by means of resetting of a feedback circuit in a differential filter when the amplitude of the high frequency signal, corresponding to the last zone of QRS group or ST pattern which is indicative of the abnormality of heart, becomes larger than a prescribed value. CONSTITUTION:Cardiogram signals Va of a subject are introduced into an input terminal 1. They are then transmitted both to a first filter 2 comprising a LPF(low pass filter) 4 and a subtractor 5, and to a second filter 3 comprising a feedback unit 8. A subtractor 5 detects the difference between a source signal Va and an output signal Vad which is provided by a LPF 4. Then, Vad is transmitted to an operational amplifier 7 in a detecting unit 6 in order to compare it with the threshold value VR. An output signal from an operational amplifier 7 is then transmitted to a second filter 3, where reset of a feedback circuit 8 is performed on condition that an equation, VR> ¦(amplitude of Vad)¦, is effective. By means of the reset of a feedback unit 8 just prior to the occurence of ringing, Vao from a second filter 3 is transmitted into a display unit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a high frequency minute electric potential generated in the late QRS or ST portion indicating an abnormality of a patient's heart from an electrocardiogram signal.

[0002]

2. Description of the Related Art It has been confirmed by basic research that an electrocardiogram of a patient who is apt to have ventricular tachycardia has a relatively high frequency minute electric potential in the late QRS or the late ST.
This minute electric potential is the rate potential (Late potential)
Say. Among patients with myocardial infarction, those with positive rate potential have a high probability of sudden death due to tachycardia. The test of rate potential has important meaning in predicting sudden cardiac death and early treatment, and is becoming popular in the clinical field as a new electrocardiographic test method.

As described above, the rate potential is a high frequency minute electric potential and does not appear on the conventional electrocardiogram wave. Therefore, a method of extracting the rate potential by applying a high-pass filter to the electrocardiogram waveform is considered.

[0004]

However, the digital filter has a phenomenon called ringing. Therefore, when a large-amplitude high-frequency portion such as an R wave is passed through the filter, the output of the filter rings during a certain time period thereafter, and the minute potential existing in the latter part of QRS and the latter part of ST is hidden. Therefore, the digital filter cannot detect the rate potential.

The present invention has been made in view of such conventional drawbacks, and an object thereof is to provide an apparatus for detecting a rate potential by a digital filter.

[0006]

According to a first aspect of the present invention, a first filter for extracting a high frequency component of an electrocardiogram signal and a QRS late stage and an ST portion of the high frequency component of the electrocardiogram signal extracted by the first filter are provided. Detecting means for detecting the presence / absence of a high frequency signal having an amplitude of a predetermined value or more, and digital filter having a feedback section and receiving the same signal as the signal supplied to the first filter to extract a high frequency component. Has a second filter in which the feedback unit is reset when the presence or absence of the signal is detected.

According to a second aspect of the present invention, in the first aspect, the second filter is a digital filter which has a feedback section and is supplied with the same signal as the signal supplied to the first filter to extract a high frequency component. The feedback unit is configured to start operating from the initial state when the detection unit detects the presence or absence of the signal.

[0008]

In the first aspect of the invention, the feedback section of the second filter is reset when the high-frequency signal having a large amplitude due to the R wave in the latter half of the QRS or the ST portion drops to a certain level during its operation. Therefore, the output of the second filter is not affected by ringing due to the R wave.

In the second aspect of the present invention, the feedback section of the second filter starts operation from the initial state when the high-frequency signal of large amplitude due to the R wave in the latter part of the QRS or the ST part is lowered to a certain level. Therefore, the output of the second filter is not affected by ringing due to the R wave.

[0010]

EXAMPLE An outline of a first example of the present invention will be described. FIG. 1 is a block diagram showing the overall configuration of the first embodiment.
The patient's electrocardiogram signal V _a shown in FIG. 2A is applied to the input terminal 1. This signal is used by the first filter 2 and the second filter
The filter 3 of FIG. The first filter 2 comprises a low pass filter 4 and a subtractor 5. The output V _ae of the low-pass filter 4 reaches the subtractor 5. The subtractor 5 calculates the difference V _ad between the signal V _a given to the input terminal 1 and the output signal V _ae of the low pass filter 4, and outputs this to the detection means 6. FIG. 2B shows the signal V _ae , and FIG. 2C shows the signal V _ad . The detection means 6 comprises a comparator 7. As shown in FIG. 2D, the comparator 7 compares the threshold value V _R with the amplitude value of the output V _ad , and outputs the result. The output of the comparator 7 reaches the second filter 3. In the second filter 3, the feedback unit 8 is reset when the output of the comparator 7 continuously becomes V _R > | (amplitude value of V _ad ) |. Here, V _R is set to a certain amplitude value of the terminal signal in the high frequency signal of the R wave. In this way, the output V of the second filter 3
_Since the feedback section 8 of _ao is reset immediately before the ringing occurs, it is not affected by the ringing. The output V _ao is shown in FIG. Figure 2 (f)
Is a plurality of electrodes attached to the patient, and X is V _ao in each of the X, Y, and Z directions orthogonal to each other with the heart as the center.
₁ , Y ₁ , Z ₁ are obtained, and from these, (X ₁ ² + Y ₁ ² +
It shows the result of calculation of Z ₁ ² ) ^1/2 .

Next, the first embodiment will be described in detail.
FIG. 3 shows the overall configuration of this embodiment. As shown in this figure, this embodiment has a CPU 10, a ROM 11 and an R.
The data processing is performed by a microcomputer composed of AM12. Each unit shown in FIG. 1 corresponds to each function of this microcomputer. The electrode 13 is attached to the patient and derives an electrocardiogram signal. The signal extracted by the electrode 13 is amplified by the amplifier 14 and A / D converted by the A / D converter 15. Although not shown in the figure, there are a plurality of sets each including the electrode 13, the amplifier 14, and the A / D converter 15, and the electrode 13 is attached to each of a plurality of positions on the patient.

The CPU 10 uses the RAM 12 and the A / D converter 15 based on the program stored in the ROM 11.
It is a circuit that processes an electrocardiogram signal given from the device and outputs the result to the display 16. Flowcharts of programs stored in the ROM 11 are shown in FIGS.

The operation of the apparatus of this embodiment thus constructed will be described. First, in step 101 in FIG. 4, signal input processing is performed. In this embodiment, the sampling rate is 1000 s / sec and about 1000 electrocardiographic waveforms are captured. This process is performed by using X, which are orthogonal to each other as described above.
This is performed for each of the electrocardiogram waveforms in the Y and Z directions. Next, in step 102 of FIG. 4, the CPU performs an adding and averaging process of the acquired waveform. This process will be described in detail with reference to FIG. First, the CPU 10 detects the first R wave segment point of the input waveform (step 201), extracts a one-period waveform centered on this segment point, and uses this as a sample (step 202). Next, the CPU detects the next R wave division point (step 203), extracts a one-cycle waveform centered on the division point, and calculates the maximum correlation position with the waveform (sample) extracted in step 202. (Step 204). Next, the CPU 10 determines whether or not the maximum correlation position is equal to or larger than the set value, that is, whether or not the waveform extracted next is added to the sample (step 205). YES here
If so (step 206), the process returns to step 203 if NO. In step 207, step 206
It is determined whether or not the noise level of the waveform obtained as a result of addition is less than or equal to a set value (request value). If NO, the process returns to step 202 (the addition result is used as a sample), and if YES, the addition result Va is stored in the RAM 12. It is stored and output to the display 13 (step 208).

Returning to FIG. 4, the description will be continued. In the next step 103, the CPU 10 separates the addition average signal Va into a high frequency signal Vad and a low frequency signal Vae. Details of this processing are shown in FIG. First, the CPU 10 takes in the arithmetic mean signal Va stored in the RAM 12 (step 30).
1) The low frequency signal Vae is obtained by the moving average process (step 302), and the high frequency signal Va is obtained by the subtraction process.
d (= Va-Vae) is calculated (step 303).

Next, the CPU 10 causes the step 104 in FIG.
Proceed to, where the threshold points are discriminated. That is, the CPU 10
Measures the amplitude in the time forward direction from the R wave position with respect to Vad obtained in step 103, and if it is determined that the amplitude is smaller than a preset threshold Vr within a preset time from a certain point, this point Is recognized as a threshold point and stored.

Next, the CPU 10 causes the step 105 in FIG.
Proceed to and perform filtering here. The filter used here is preferably a 4th-order IIR Butterworth high-pass filter. The structure of this filter is shown in FIG. When the threshold value obtained in step 104 is reached during the filtering process using this filter, the CPU 10 resets all the amplifiers b ₁ , b ₂ , b ₃ , b ₄ on the feedback side shown in FIG. To In this way, the feedback side is reset before the ringing due to the R wave occurs, and thus the link X does not appear in the output Xo (n) of the entire filter, that is, Vao. Next, the CPU 10 obtains (X ₁ ² + Y ₁ ² + Z ₁ ² ) ^1/2 from X ₁ , Y ₁ and Z ₁ which are Vao in the X, Y and Z directions (step 10
6) The result is stored and output to the display 16 (step 107).

8 (a), 8 (b) and 8 (c) show signals Va and Vao of a person who has no heart disease (both X and
Signals in Y and Z directions) and (X ₁ ² + Y ₁ ² +
Z ₁ ² ) ^1/2 is shown in FIG. 9 (a), (b),
Signals Va, Vao (X ₁
² + Y ₁ ² + Z ₁ ² ) ^1/2 is shown. As shown in these figures, since the ringing does not appear in the high frequency signal appearing in the latter part of QRS or in the ST part, the original high frequency minute signal at that time can be accurately obtained.

Next, a second embodiment will be described. In this embodiment, the filtering process of step 105 in FIG. 4 in the first embodiment is started from the threshold point obtained in step 104. That is, the outputs of the amplifiers b ₁ , b ₂ , b ₃ , b ₄ on the feedback side are set to 0 until the threshold point is reached, and the state is canceled when the threshold point is reached. At this time, the operation of the filter in the forward direction may be stopped until reaching the threshold point, and the operation may be started at the same time as the feedback side, or the operation may be performed before reaching the threshold point. In any case, the required data is Q
Since it is a high frequency minute signal in the late RS or ST part,
Also in this embodiment, a necessary high frequency minute signal can be obtained without being affected by ringing. In the present embodiment, the effectiveness of the rate potential generated in the latter half of QRS has been described, but it is also effective in detecting the atrial rate potential occurring in the latter half of the P wave and the minute His bundle potential generated subsequent to the P wave. Can be utilized.

[0019]

According to the present invention, the rate potential can be accurately detected by using a digital filter without being affected by ringing.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an outline of a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the apparatus shown in FIG.

FIG. 3 is a diagram showing a specific configuration of the first embodiment of the present invention.

FIG. 4 is a diagram for explaining the operation of the first embodiment of the present invention.

FIG. 5 is a diagram for explaining the operation of the first embodiment of the present invention.

FIG. 6 is a diagram for explaining the operation of the first exemplary embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a digital filter used in the first embodiment of the present invention.

FIG. 8 is a diagram showing an example of output waveforms according to the first embodiment of the present invention.

FIG. 9 is a diagram showing an example of output waveforms according to the first embodiment of the present invention.

[Explanation of symbols]

 2 first filter 3 second filter 6 detecting means

Claims (2)

[Claims] 1. A first extracting a high frequency component of an electrocardiogram signal
Of the high frequency component of the electrocardiogram signal extracted by the first filter and the latter QRS and ST
A detection means for detecting the presence / absence of a high frequency signal having an amplitude equal to or larger than a predetermined value in a portion, and a digital filter having a feedback section and receiving the same signal as the signal given to the first filter to take out a high frequency component. A second filter in which the feedback section is reset when the detection means detects whether the signal is present or absent. 2. A first extracting a high frequency component of an electrocardiogram signal
Of the high frequency component of the electrocardiogram signal extracted by the first filter and the latter QRS and ST
A digital filter having a detector for detecting the presence or absence of a high frequency signal having an amplitude equal to or less than a predetermined value in a portion, and a digital filter for extracting a high frequency component given the same signal as the signal given to the first filter, A high-frequency micro-potential detecting device comprising: a second filter in which the feedback section starts operation from the initial state when the detecting means detects the presence or absence of the signal.