JPH0357433A - Electrocardiograph - Google Patents

Abstract

PURPOSE:To record a cardiogram waveform with high accuracy, and also, extending over many hours by varying data compressibility in accordance with an output from a data comprssibility varying means. CONSTITUTION:Cardiogram electrodes installed in a person to be examined are connected to input terminals 5 of an amplifying part 10, and a detected cardiogram signal is amplified by the amplifying part 10, inputted to an A/D converting part 20, and inputted as a digital signal to a control part 30. The control part 30 executes data compression in order to store the inputted digital signal into a memory part 40 of the finite capacity. As for a method for the data compression, for instance, an AZTEC method, or an SAPA method, etc., are available. The AZTEC method is a method for omitting the data of the part whose variation is comparatively small by varying a threshold related to a differential value. The SAPA method is that which compresses the data by polygonal line approximation, and by changing an error rate by minuteness of the number of points for connecting the polygonal lines, the compressibility is varied.

Description

[Detailed Description of the Invention] [Industrial Application Field] In recent years, heart disease has been on the rise among adult diseases, and the increase in ischemic heart disease in particular is becoming a social problem. The most common test for heart disease is the 12-lead electrocardiogram, but since this test is a very short-term electrocardiogram and is done during rest, it is not suitable for cases such as excessive angina pectoris. At present, it is of little use.

In addition, exercise stress electrocardiography is a test that detects abnormal electrocardiograms that cannot be detected with resting electrocardiography, but this test is a method of inducing an abnormal state, so it is risky, and the testing time is naturally limited. be.

Long-term electrocardiography (commonly known as Holter electrocardiography) is a safe and excellent method for detecting transient abnormal electrocardiograms.

However, in the Holter heart 74 diagram test, a magnetic tape device is carried around for 24 hours, all heart diagrams for 24 hours are recorded, and after the test, analysis is performed during high-speed playback. It is large and heavy, which makes it difficult to carry.Furthermore, because the magnetic tape runs at low speed to record all 24-hour electrocardiograms, the frequency characteristics deteriorate and the electrocardiogram waveform becomes distorted. There is a problem with this.

In order to solve the problem of poor portability and waveform distortion, attempts have been made to use semiconductor memory instead of magnetic tape.

[Problem to be solved by the invention]

By the way, in order to record all electrocardiogram waveforms for 24 hours, a storage capacity of about 22 Mbyte is required even for an I-lead test. That is, if the heart rate is 60 BPM, the electrocardiogram will be approximately 100,000 beats in 24 hours, and sampling at 250 Hz (4 ms) or more is required to record the waveform without distortion. Therefore, 24 hours, 4
With ms sampling, the total number of data is 250x60x6
0x24=21.6X10', and if the A/D converter precision is 8 bits, then it is 21.6 Mbytes. For this reason, even if the current semiconductor memory is used, the circuit scale becomes large, and it is difficult to achieve a significant reduction in size and weight compared to magnetic tape devices.

As a way to reduce the huge amount of electrocardiogram data for 24 hours, a data compression method has been proposed (Japanese Unexamined Patent Publication No. 1982-19229), but in order to reduce the amount of data, If the compression ratio is increased, the fidelity of the electrocardiogram waveform to its original waveform will be lost, which may pose a serious problem in diagnosis.

The present invention is intended to solve the above problems, and is an electrocardiogram capable of recording electrocardiogram waveforms with high accuracy over a long period of time by improving portability and performing appropriate data compression for the purpose of electrocardiogram testing. The purpose is to provide a

[Means to solve the problem]

The present invention provides an electrocardiogram electrode that extracts an electrocardiogram signal, and an A/C converter that converts an analog signal from the electrocardiogram electrode into a digital signal.
In an electrocardiograph comprising a D converter, a control means for data compressing the digital signal from the A/D converter, and a memory for storing the output from the control means, the control means includes data compression rate variable means. It is characterized by changing the data compression rate depending on the output, and also depending on whether it is normal or abnormal.
Alternatively, the data compression rate can be changed by operating an event switch.

[Effect]

The electrocardiograph of the present invention is designed to capture electrocardiogram waveform data by changing the data compression rate.The data compression rate is lowered for detailed examinations, and is used for general examinations such as screening. By increasing the compression rate and collecting data, it can be applied to a wide range of applications depending on the diagnostic purpose.Also, by lowering the data compression rate during abnormal times and increasing it during normal times, it is possible to collect data over a long period of time. While doing
In addition, it becomes possible to collect detailed data when an abnormality occurs.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the electrocardiograph of the present invention;
FIG. 2 is a diagram showing electrocardiogram waveforms obtained when changing the data compression rate. In the figure, 5 is an input terminal, 10 is an amplification section, 20 is an A/D conversion section, 30 is a control section, 40 is a memory section, 50 is a power supply section, and 60 is a data compression ratio variable section.

In FIG. 1, electrocardiogram electrodes (not shown) attached to the subject are connected to the human power terminal 5 of the amplifier 10, the detected electrocardiogram signal is amplified by the amplifier 10, and the A/D converter 20 and is taken into the control unit 30 as a digital signal. The control unit 30 performs data compression to store the captured digital signal in the finite capacity memory B40.

As a data compression method, for example, the AZTEC method or the SAPA method may be used.

The AZTEC method is a method of omitting data in parts with relatively little change by changing the threshold regarding the differential value.
The waveform obtained when changing the compression ratio is shown in Figure 2 (a).
It will look like the one shown below. In the figure, (a) is the original waveform, which is sequentially 1/1.8, 1/2.7, 1/3.4,
Waveforms at compression ratios of 1/4, 9, 1/5.5, and 1/6.6 are shown.

For example, if the compression ratio is set to 1/6.6 as shown in FIG. However, the electrocardiogram waveform (G) has waveform distortion compared to the original waveform (B), which may impede detailed waveform diagnosis. However, rough diagnosis is possible with this degree of distortion, so the compression ratio can be adjusted depending on the purpose of diagnosis by lowering the compression ratio for precise diagnosis and increasing the compression ratio for rough diagnosis. The fidelity of the recorded electrocardiogram waveform can be varied.

The SAPA method compresses data using polygonal line approximation, and the error '2 = (ratio of the difference between the true value and the value on the polygonal line to the true value) ε due to the fineness of the number of points connecting the polygonal lines.
Change the compression ratio by changing .

That is, as shown in FIG. 2b), as ε increases, the compression ratio increases.

The data pressure N rate variable unit 60 in FIG. 1 allows the examiner to specify the data compression rate according to the purpose of diagnosis (examination), and specifically allows the value of the compression rate to be selected from the outside. .

Then, the control section 30 changes the compression-related parameters using the method described above in accordance with the compression rate manually input by the data compression rate variable section 60, and performs data compression.

The power supply 150 is composed of, for example, a battery, and supplies power to each part.

FIG. 3 is a block diagram of another embodiment of the invention.

The difference from FIG. 1 is that a memory card 70 is used as an external storage medium in addition to the memory section 40 in order to increase the storage capacity of electrocardiogram data. In this case too,
The control unit 30 performs data compression based on the compression rate specified by the data compression rate variable unit 60, and the memory card 7
While the 0 capacity is filled and the memory card is replaced, data at the time of replacement can be temporarily stored in the memory section 40 to prevent data loss. Then, when a new memory card is set, all data temporarily stored in the memory section 40 will be stored in the new memory card.

FIG. 4 is a block diagram showing another embodiment of the present invention.

In this implementation, the digital output of the A/D converter 20 is read by the abnormality determining unit 80 for a predetermined period of time, and as shown in FIG. When it is short, it is assumed to be normal, when it is normal, the compression rate is increased, and when it is abnormal, the compression rate is lowered and the original waveform or data close to it is imported.

Of course, values other than W, such as waveform area, waveform height, timing, etc., may be used as appropriate. In this embodiment, data can be compressed and accurate data can be obtained in the event of an abnormality.

FIG. 6 is a block diagram of another embodiment of the invention.

In this embodiment, an event switch 90 is provided, and when the subject becomes aware of a symptom, the patient operates the event switch to change the parameter output from the data compression rate variable section to lower the data compression rate and to detect abnormal conditions. The data is recorded in detail, and in this case as well, data can be compressed and precise data can be obtained in the event of an abnormality.

〔Effect of the invention〕

As described above, according to the present invention, an electrocardiograph, for example, a long-term electrocardiograph, is provided with a data compression rate variable section that can vary the compression rate of digital electrocardiogram data to be stored, so that it can be adjusted according to the purpose of examination. Since the compression rate of the electrocardiogram waveform stored can be selected, it is possible to provide an electrocardiograph that can be used for many purposes, from screening diagnosis to detailed diagnosis. Furthermore, by lowering the data compression rate during abnormal times and increasing it during normal times, it becomes possible to increase the amount of collected data and to collect finely detailed data during abnormal times.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the electrocardiograph of the present invention;
Fig. 2 is a diagram showing electrocardiogram waveforms obtained when changing the data compression rate, Fig. 3 is a block diagram of another embodiment of the present invention equipped with a memory card, and Fig. 4 shows whether it is normal or abnormal. FIG. 5 is a block diagram of another embodiment of the present invention in which the compression ratio is changed accordingly, FIG. 5 is a diagram showing an electrocardiogram waveform, and FIG. 6 is a block diagram of another embodiment of the present invention in which an event switch is provided. It is. 5...Input terminal, 10...Amplification section, 20...Δ/
D conversion section, 30... control section, 40... memory section, 5
0...Power supply section, 60...Data compression rate variable section, 70
... Abnormality judgment section, 80 ... Event switch. Applicant Terumo Corporation

Claims (2)

[Claims] (1) A detection unit that extracts an electrocardiogram signal, an A/D converter that converts an analog signal from the detection unit into a digital signal, a control unit that compresses the digital signal from the A/D converter, and 1. An electrocardiograph comprising a memory for storing an output from a control means, wherein the control means changes a data compression rate in accordance with an output from a data compression rate variable means. (2) The control means includes an abnormality determination unit that determines whether the electrocardiogram signal is abnormal based on the digital signal from the A/D converter, and the data compression rate variable means adjusts the data compression rate according to the determination result of the abnormality determination unit. The electrocardiograph according to claim 1, characterized in that the output to the control section is changed.