Electrocariographic method

Abstract: An electrocardiograph which comprises a detecting circuit (1) for detecting a cardiographic signal from a living body; a storage circuit (4) for storing the cardiographic signal from the detecting circuit; a storage control circuit (5) capable of performing a sto­ rage control operation in such a way as to sequentially and continu­ ously store a new cardiographic signal in the storage circuit (4) for the formation of cardiographic data and as to successively erasing old ones of the cardiographic data which are stored in the storage circuit (4); and a cardiographic data hold commanding circuit (5) operable in response to a cardiographic data hold commanding signal to command to retain the cardiographic data in the storage circuit (4).

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to an electrocardiographic method capable of providing electrocardiographic data. Description of the Prior Art: As an electrocardiograph, Holter electrocardiograph is well known. Holter electrocardiograph is so designed as to monitor a cardiographic signal, detected from a living body, continuously for 24 hours at maximum and record electrocardiographic data on an analog tape. A patient whose cardiographic data are required may be a patient suffering from angina pectoris decubitus, i.e, the patient who tends to have a heart attack, for example, once a week. The patient suffering from this disease is generally required to provide cardiographic data from time to time and, therefore, with Holter electrocardiograph, a roll of recording tape has to be supplemented each day while a number of rolls of recording tape has to be stocked for the time of use. Apart from Holter electrocardiograph, a handy electrocardiograph is also well known which can provide cardiographic data when the patient operates it in the event of the heart attack. While this known handy electrocardiograph is effective to provide useful cardiographic data at the time of occurrence of the heart attack, it cannot provide abnormal cardiographic data which do not show the occurrence of heart attack during, for example, sleeping. A method having the features of a first portion of appended claim 1 up to and including step (b) is known from the US patent US-A-4,653,022 except the feature of the provision of the second hold commanding signal. In contrast, an article of N. V. Thakor et al published in Medical and Biological Engineering and Computing, Vol. 22, 1984, pages 151 - 159, having the title "Design, implementation and evaluation of a microcomputer-based portable arrhythmia monitor" comprises all features of said first portion of appended claim 1, except the provision of the first hold commanding signal. The document GB-A-2 034 048 discloses that in a method of operating an electrocardiograph first and second hold commanding signals, as defined in the preamble of appended claim 1, can be provided arbitrarily. SUMMARY OF THE INVENTION It is the object of the present invention to provide a method of operating an electrocardiograph which stores special information as it occurred before and after an abnormal event. The method of the present invention is defined by the teaching of appended claim 1. One of its essential features is that data as they were stored before the occurrence of an abnormal event are kept unchanged in a latter part of a storage means, even when the data in an initial part of the storage means are changed continuously, as long as no further hold commanding signal is provided or for a predetermined period of time after one of the two hold commanding signals is provided. BRIEF DESCRIPTION OF THE DRAWINGS This and other objects and features of the present invention will become clear from the following description taken in conjunction with a preferred embodiment thereof with reference to the accompanying drawings, in which: Fig. 1 is a block circuit diagram showing the overall structure of an electrocardiograph according to the present invention; Fig. 2 is a flow chart showing the sequence of operation of the electrocardiograph shown in Fig. 1; Figs. 3 to 5 are explanatory diagrams used to explain the operation of a recording unit; and Fig. 6 is a fragmentary cardiogram used to illustrate the determination of the presence or absence of an abnormality. DETAILED DESCRIPTION OF THE EMBODIMENT Referring first to Fig. 1, reference numeral 1 represents a sensor (a detecting means); reference numeral 2 represents an amplifier circuit; reference numeral 3 represents an analog-to-digital converter (A/D); reference numeral 4 represents a recording unit (a storage means); and reference numeral 5 represents a control circuit (a storage control means, a hold commanding means). A cardiographic signal provided from the sensor 1 which is held in contact with a living body is amplified by the amplifier circuit 2 and is then converted into a digital signal by the A/D converter 3 which performs an A/D conversion in response to an A/D conversion command supplied from the control circuit 5, which digital signal is stored in the recording unit 4 from time to time. In the recording unit 4, on the basis of a storage control signal supplied from the control circuit 5, a new digital cardiographic signal is stored so as to form cardiographic data sequentially and continuously, and the stored cardiographic data are erased in the order from older ones while a predetermined quantity of cardiographic data are successively updated and stored. Reference numeral 6 represents an external input unit such as a keyboard and reference numeral 7 represents a discriminating circuit. A start signal and a first hold commanding signal, as will be described later, are supplied by inputting from the external input unit 6 to the control circuit 5, and the discriminating circuit 7 determines the presence or absence of abnormality in the new digital cardiographic signal which is being stored in the recording unit 4 and generates a second hold commanding signal (an abnormality signal) to the control circuit 5 in the event of the presence of abnormality. The determination of the presence or absence of abnormality performed by the discriminating circuit 7 is carried out in such a manner that, assuming that the cardiographic signal obtained represents, for example, such a waveform as shown in Fig. 6, if the heart rate (1/R₁ ∼ R₂ hour) is within the range of 50 to 100 per minute, the absence of abnormality can be determined, but if the heart rate is out of the above range, the presence of abnormality such as bradycardia or tachycardia can be determined. The first and second hold commanding signals referred to above are a cardiographic data hold commanding signal of the present invention and are applied to the recording unit 4 through the control circuit 5, and the recording unit 4 is adapted to retain all of the stored contents being updated and stored in response to the first hold commanding signal and a later half of the stored contents in response to the second hold commanding signal. The operation of the above described embodiment will now be described with reference to the flow chart of Fig. 2 showing the sequence of operation of the control circuit 5. The operation starts when an electric power source switch is turned on or any other reason, and a decision is made at step S1 and then at step S2 to determine the presence or absence of the first hold commanding signal and then that of the second hold commanding signal. Should no one of the first and second hold commanding signals be present, the A/D conversion commanding signal and the storage control signal are supplied from the control circuit 5 to the A/D converter 3 and the recording unit 4, respectively, causing the recording unit 4 to sequentially and continuously store the digital cardiographic signal supplied from the A/D converter 3 at step S3. At the time of initiation, the recording unit 4 stores nothing and is in an all cleared state and, each time the flow from step S1 back to step S1 via steps 2 and 3 is repeated, the storage amount thereof is increased. After storage areas are filled, as shown in Fig. 3, the oldest data portion Dn is erased each time a new digital signal Do is applied, that is, the cardiographic data stored are updated at step S3 with passage of time. The first hold commanding signal referred to above is applied when the patient suffering from the attack inputs it by manipulating the external input unit 6, whereas the second hold commanding signal is applied from the discriminating circuit 7 in the event of occurrence of abnormality in the cardiographic signal. Should the result of decision at step S1 indicate the presence of the first hold commanding signal, the length of time passed subsequent to the generation of the first hold commanding signal is counted at step S4. Since the counted length of time has not yet exceeded a preset value immediately after the generation of the first hold commanding signal, updating and storage operation is carried out at step S5 in a manner similar to that at step S3 and the program flow then return to step S4. The updating and storage operation at step S5 is repeated before the counted length of time exceeds the preset value and, thereafter, i.e., after the passage of the preset length of time, the program flow proceeds to step S6 at which the whole of the cardiographic data D₁ to D n then stored are retained with the updating interrupted, with the operation subsequently terminating when the hold command is outputted from the control circuit 5. As hereinabove described, since subsequent to the generation of the first hold commanding signal at step S1, the updating and storage operation at step S5 is repeated a plurality of times before the preset time passes, the cardiographic signal available at the time of generation of the first hold commanding signal occupies a position intermediate of the cardiographic data retained, that is, the cardiographic data including those portions before and after the outputting of the first hold commanding signal are retained in the recording unit 4. The hold signal outputted at step S7 is used as a warning signal for a retention alarm 8 which may be optionally used, and the retention alarm 8 if used may be a warning ring capable of generating warning sounds, a display providing a visual warning display, a waning lamp or a combination thereof, provided that owing to the indication provided by the retention alarm 8 the hold operation can be confirmed from the outside on a real-time basis. In the event that the result of decision at step S2 indicates that the abnormality is found in the cardiographic signal and that the second hold commanding signal has been generated, a decision is made at step S8 to determine the presence or absence of the first hold commanding signal and, in a manner similar to the repeated flow from step S4 back to step S4 via step S5, the program flow is repeated from step S9 back to step S9 via step S10, followed by the retention at step S11 of a later half (date D m+1 to D n ) of the cardiographic data to be stored as shown in Fig. 4 with the abnormal cardiographic signal retained at the intermediate position. Thereafter, the hold signal therefor is outputted at step S12 in a manner similar to that at step S7. From step S8, the program flow proceeds to step S4, and the flow from any one of steps S2 and S10 to step S8 is caused to occur so that, even after the presence of the second hold commanding signal has been once determined, priority can be given to a corresponding operation in relation to the first hold commanding signal in the event of the presence of the first hold commanding signal. After the generation of the hold command at step S12, a decision is made at step S13 to determine the presence or absence of the first or second hold commanding signal. In the event of the absence of both of the first and second hold commanding signals, as shown in Fig. 5, the updating and storage operation of the remaining first half (data D o to D m ) of the cardiographic data is carried out at step S14. Should the presence of the hold command be found at step S13, the program flow proceeds to step S4, and the holding operation at step S6 in that case is carried out in the first half of the data wherefore both of the first half and latter half of the cardiographic data can be retained in the recording unit 4. The retained data so obtained can be displayed by a display unit, integrated with the electrocardiograph or connected therewith, in response to a manipulation done to effect the display. In the foregoing embodiment, the number of divisible memory areas in the recording unit 4 has been shown as two, but it may be possible to increase it to a number greater than two so that the number of times of retention resulting from the first or second hold commanding signal can be increased thereby enabling a plurality of retained data to be obtained for each cycle of operation. Also, the recording unit 4 may be so constructed that some other data useful for the diagnosis of the cardiographic data such as the time of detection, the heat rate trend, ST trend, etc., can be recorded simultaneously. Also, in the foregoing embodiment of the present invention, arrangement has been made that the retaining operation can be performed by the first or second hold commanding signal. However, it is possible to make the retaining operation to be performed relying only on a hold commanding signal corresponding to the second hold commanding signal and, in such case, arrangement may be made so that the retained data can be cancelled by depressing a cancel key which may be depressed by the patient when no attack occur while data can be obtained in the event of the occurrence of the attack. Since the present invention is so constructed as hereinabove fully described, that is, since the cardiographic data can be updated and stored in the storage means with passage of time and retained in response to the hold command issued from the hold commanding means, the electrocardiograph according to the present invention is effective in that the necessary cardiographic data can be easily obtained within the framework of the limited storage capacity.

Claims: A method of operating an electrocardiograph which includes a control means (5), a cardiographic sensor (1) for sensing cardiographic data (D1 - Dn), a storage means (4) for storing such data, an input means (6) for inputting a first hold commanding signal into said control means, and a discriminator means (7) for discriminating whether an abnormality is present within said cardiographic data, and for outputting a second hold commanding signal if this is the case to said control means, said control means commanding, when receiving said first or second hold commanding signals, said storage means to store cardiographic data; said method comprising the steps of: (a) storing data, till one of said hold commanding signals is inputted into said control means, within said storage means in a way that in a sequential series of data all data are shifted by one position and the oldest data is discarded when a new data is stored in the first address; and (b) when said second hold commanding signal is provided, storing data for a first predetermined period of time in the way as defined in step (a), which period has such a length that a part of the data stored before said second hold commanding signal was provided, remains within a latter part of said storage means; the method further comprising the following steps: (c) keeping (S11) the data (Dm+1 - Dn) within the latter part of said storage means unchanged in all further steps; (d) detecting (S13) whether one of said hold commanding signals is provided after the end of said first period of time, and performing the following steps when this is not the case; (e) shifting the old data within the initial part of said storage means and discarding the oldest data when a new data is stored into the first address of the storage means (S14); and (f) returning to step (d). The method of claim 1, further comprising the step of generating an alarm after said first period of time has elapsed. The method of claim 1 or claim 2, wherein, when it is detected in step (d) (S13) that one of said hold commanding signals is provided, the following step is performed: (g) shifting, for a predetermined second period of time, all data within the initial part of said storage means and discarding the oldest data within said storage means when a new data is stored into the first address of said storage means (S4, S5). The method of claim 3, further comprising the step of generating an alarm after said second period of time has elapsed.

Inventors: SUZUKI TAKASHI - - KOAZA MITSU, SUZUKI, TAKASHI 21-404, 48-1, KOAZA MITSUBADANI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1989
Main classification: A61B5
IPC codes: A61B5