Atrial fibrillation detector, atrial fibrillation detecting method, and computer readable medium

An atrial fibrillation detecting device includes a processor and a memory that stores a computer-readable command. When the computer-readable command is executed by the processor, the atrial fibrillation detecting device is configured to acquire pulse data representing a plurality of pulses, calculate a pulse rate based on the pulse data, calculate respective pulse amplitude indices of the plurality of pluses based on the pulse data, calculate an amplitude dispersion of the pulse amplitude indices based on the calculated pulse amplitude indices, calculate respective pulse interval indices of the plurality of pluses based on the pulse data, calculate an interval dispersion of the pulse interval indices based on the calculated pulse interval indices, and determine whether the pulse data is atrial fibrillation, based on the calculated pulse rate, the calculated amplitude dispersion, and the calculated interval dispersion.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Applications No. 2016-251031 filed on Dec. 26, 2016, the contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to an atrial fibrillation detecting device and an atrial fibrillation detecting method. In addition, the present disclosure relates to a computer-readable storage medium in which a program for making a computer execute the atrial fibrillation detecting method is stored.

Japanese Patent No. 5336803 discloses a pulse measuring device which calculates each pulse amplitude and each pulse interval respectively, calculates a product of the pulse amplitude and the pulse interval and a ratio between the pulse amplitude and the pulse interval, and determines that the pulses indicate an arrhythmia, based on the product of the pulse amplitude and the pulse interval and the ratio between the pulse amplitude and the pulse interval.

However, the pulse measuring device disclosed in Japanese Patent No. 5336803 can determine whether the pulses indicate an arrhythmia or not, but cannot determine whether the pulses indicate premature ventricular contraction or indicate atrial fibrillation.

The present disclosure is to provide an atrial fibrillation detecting device and an atrial fibrillation detecting method which detects atrial fibrillation more accurately.

Further, the present disclosure is to provide a computer-readable storage medium in which a program for making a computer execute the atrial fibrillation detecting method is stored.

SUMMARY

According to an aspect of the present disclosure, an atrial fibrillation detecting device includes a processor and a memory that stores a computer-readable command. When the computer-readable command is executed by the processor, the atrial fibrillation detecting device acquires pulse data representing a plurality of pulses, calculates a pulse rate based on the pulse data, calculates respective pulse amplitude indices of the plurality of pluses based on the pulse data, calculates an amplitude dispersion of the pulse amplitude indices based on the calculated pulse amplitude indices, calculates respective pulse interval indices of the plurality of pluses based on the pulse data, calculates an interval dispersion of the pulse interval indices based on the calculated pulse interval indices, and determines whether the pulse data is atrial fibrillation, based on the calculated pulse rate, the calculated amplitude dispersion, and the calculated interval dispersion.

According to another aspect of the present disclosure, an atrial fibrillation detecting method that is executed by a computer includes acquiring pulse data representing a plurality of pulses, calculating a pulse rate based on the pulse data, calculating respective pulse amplitude indices of the plurality of pluses based on the pulse data, calculating an amplitude dispersion of the pulse amplitude indices based on the calculated pulse amplitude indices, calculating respective pulse interval indices of the plurality of pluses based on the pulse data, calculating an interval dispersion of the pulse interval indices based on the calculated pulse interval indices, and determining whether the pulse data is atrial fibrillation, based on the calculated pulse rate, the calculated amplitude dispersion, and the calculated interval dispersion.

According to the present disclosure, it is possible to provide an atrial fibrillation detecting device and an atrial fibrillation detecting method which detects atrial fibrillation more accurately. Further, according to the present disclosure, it is possible to provide a computer-readable storage medium in which a program for making a computer execute the atrial fibrillation detecting method is stored.

DETAILED DESCRIPTION OF EMBODIMENTS

A presently disclosed subject matter will be described below with reference to the drawings. Incidentally, description about elements having one and the same reference signs as elements which have already been described in description of the presently disclosed subject matter will be omitted for convenience of explanation.

FIG. 1illustrates a hardware configuration diagram of an atrial fibrillation detecting device1according to the presently disclosed subject matter. As illustrated inFIG. 1, the atrial fibrillation detecting device1(which will be hereinafter referred to as detecting device1simply) may include a controller2, a storage3, a network interface4, a display5, and an input operation unit6, which are connected to one another communicably through a bus8.

The detecting device1may be a medical dedicated device (such as a patient monitor) for displaying a trend graph or a list of vital data. For example, a personal computer, a work station, a smartphone, a phablet, a tablet, or a wearable device (such as an Apple Watch or a smart glass) which is mounted on a body part (such as an arm or the head) of an operator (medical care provider) may be used as the detecting device1.

The controller2may include a memory and a processor. The memory is configured to store computer-readable commands (programs). For example, the memory is constituted by an ROM (Read Only Memory) in which various programs etc. have been stored, an RAM (Random Access Memory) which has a plurality of work areas where the various programs etc. to be executed by the processor can be stored, etc. For example, the processor may be a CPU (Central Processing Unit), an MPU (Micro Processing Unit) and/or a GPU (Graphics Processing Unit), which is configured to expand a program onto the RAM to execute various processes in cooperation with the RAM. The program is specified from the various programs which have been incorporated in the ROM.

The controller2may control various operations of the detecting device1in such a manner that, particularly, the processor expands an atrial fibrillation detecting program for executing an undermentioned atrial fibrillation detecting method onto the RAM, and executes the atrial fibrillation detecting program in cooperation with the RAM. The controller2and the atrial fibrillation detecting program will be described later in detail.

For example, the storage3is a storage device (storage) such as an HDD (Hard Disk Drive), an SSD (Solid State Drive) or a USB flash memory, which is configured to store the programs or various data. The atrial fibrillation detecting program may be incorporated in the storage3. In addition, ECG data representing an ECG waveform or pulse data representing pulses may be stored in the storage3. The ECG data are acquired by a not-illustrated ECG sensor. Further, the pulse data are acquired by a not-illustrated pulse sensor. The acquired ECG data or the acquired pulse data may be stored into the storage3through a communication network or through a storage medium such as a USB memory, or may be stored into the storage3through a sensor interface (not illustrated) connected to the ECG sensor or the pulse sensor. As shown inFIG. 4, the ECG waveform is constituted by heartbeat waveforms occurring continuously along a time axis (see an ECG waveform display region R1). In addition, the pulses occur continuously along the time axis (see a pulse display region R2).

The network interface4is configured to connect the detecting device1to the communication network. Specifically, the network interface4may include various wired connection terminals for making communication with an external device such as a server through the communication network, and various processing circuits for wireless connection. The network interface4is configured to be conformed to communication standards for making communication through the communication network. Here, the communication network may be an LAN (Local Area Network), a WAN (Wide Area Network), the Internet, or the like. For example, the atrial fibrillation detecting program or the vital data (the ECG data or the pulse data) may be acquired through the network interface4from a computer disposed on the communication network.

The display5may be a display device such as a liquid crystal display, an organic EL display, or a transmissive type or non-transmissive type head mount display which is to be mounted on the head of the operator. For example, as illustrated inFIGS. 4 to 6, a physiological information display screen10is displayed on a display screen of the display5.

The input operation unit6accepts an input operation from the operator operating the detecting device1, and is configured to generate an instruction signal in response to the input operation. For example, the input operation unit6is a touch panel superimposed and disposed on the display5, operation buttons attached to a housing, a mouse or a keyboard, or the like. The instruction signal generated by the input operation unit6is transmitted to the controller2through the bus8. The controller2executes predetermined processing in accordance with the instruction signal.

Next, an example of the atrial fibrillation detecting method according to the presently disclosed subject matter will be described with reference toFIGS. 2 to 4.FIG. 2is a flow chart for explaining the example of the atrial fibrillation detecting method according to the presently disclosed subject matter.FIG. 3is a flow chart for explaining an example of a method for visibly displaying a pulse rate, a dispersion Da of peak amplitude values Ap and a dispersion Dt of peak-to-peak time intervals Tp on a pulse analysis result display region R3(seeFIG. 4).FIG. 4is a view illustrating an example of the physiological information display screen10which may include the pulse analysis result display region R3displayed as a two-dimensional coordinate system.

As shown inFIG. 2, first, the controller2acquires pulse data of a patient (step S10). For example, the controller2may acquire the pulse data of the patient from the storage3, or may acquire the pulse data through the network interface4from an external device disposed on the communication network. The controller2may acquire ECG data of the patient together with the pulse data of the patient in the step S10.

Next, the controller2calculates a pulse rate of the patient based on the acquired pulse data (step S11). Here, the pulse rate is a number of arterial pulses in one minute. In other words, the pulse rate corresponds to a number of pulses appearing in one minute. The controller2may calculate the pulse rate from the pulse data by use of a well-known analysis method. For example, after having acquired each of peak-to-peak time intervals Tp (an example of a pulse interval index) between adjacent ones of the pulses, the controller2calculates an average peak-to-peak time interval Tav of the peak-to-peak time intervals Tp. As illustrated inFIG. 4, each of the peak-to-peak time intervals Tp corresponds to a time interval between one peak point and the other point of two adjacent pulses. Then, the controller2may calculate a value (60 [sec]/Tav [sec]) which is obtained by dividing 60 seconds by the average peak-to-peak time interval Tav, as the pulse rate.

Next, the controller2calculates each of peak amplitude values Ap (an example of a pulse amplitude index) of a plurality (or all) of pulses contained in the pulse data based on the acquired pulse data (step S12). As shown inFIG. 4, each of the peak amplitude values Ap corresponds to an amplitude value of a pulse at a peak point thereof. Then, the controller2calculates a dispersion Da of the peak amplitude values Ap based on the calculated peak amplitude values Ap (step S13). For example, first, the controller2calculates a standard deviation σ of the peak amplitude values Ap, and calculates an average value Ap_av of the peak amplitude values Ap. Next, the controller2divides the calculated standard deviation σ of the peak amplitude values Ap by the average value Ap_av of the peak amplitude values Ap (standard deviation σ/average value Ap_av), so that a dispersion Da of the peak amplitude values Ap can be calculated. When the standard deviation σ is divided thus by the average value Ap_av, the dispersion Da (Da<1) can be normalized.

In a step S14, the controller2calculates each of a plurality (or all) of peak-to-peak time intervals Tp (an example of a pulse interval index) contained in the pulse data. Incidentally, when the pulse rate is specified based on the peak-to-peak time intervals Tp in the step S11, the processing of the step S14may be executed in the step S10. Then, the controller2calculates a dispersion Dt of the peak-to-peak time intervals Tp based on the calculated peak-to-peak time intervals Tp (step S15). For example, first, the controller2calculates a standard deviation σ of the peak-to-peak time intervals Tp, and calculates an average value Tp_av of the peak-to-peak time intervals Tp. Next, the controller2divides the calculated standard deviation σ of the peak-to-peak time intervals Tp by the average value Tp_av of the peak-to-peak time intervals Tp (standard deviation σ/average value Tp_av), so that a dispersion Dt of the peak-to-peak time intervals Tp can be calculated. When the standard deviation σ is divided thus by the average value Tp_av, the dispersion Dt (Dt<1) can be normalized.

Then, in a step S16, the controller2determines whether the specified pulse rate exceeds a threshold PRth (first threshold) or not. The threshold PRth may be changed suitably in accordance with an input operation performed by the medical care provider on the input operation unit6. For example, the threshold PRth is 100 (times/minute). When it is determined that the calculated pulse rate exceeds the threshold PRth (YES in the step S16), the processing goes to a step S17. On the other hand, when it is determined that the calculated pulse rate does not exceed the threshold PRth (NO in the step S16), the processing goes to a step S20. In the step S20, the controller2determines that the pulse data of the patient do not indicate atrial fibrillation. In this case, the controller2may determine that the pulse data of the patient indicate regular pulses (normal sinus rhythm) or premature ventricular contraction.

Next, the controller2determines whether the calculated dispersion Da of the peak amplitude values Ap exceeds a threshold Da_th (second threshold) or not (step S17). The threshold Da_th may be changed suitably in accordance with an input operation performed by the medical care provider on the input operation unit6. For example, Da_th is 0.2. When it is determined that the calculated dispersion Da exceeds the threshold Da_th (YES in the step S17), the processing goes to a step S18. On the other hand, when it is determined that the calculated dispersion Da does not exceed the threshold Da_th (NO in the step S17), the processing goes to the step S20.

Next, the controller2determines whether the calculated dispersion Dt of the peak-to-peak time intervals Tp exceeds a threshold Dt_th (third threshold) or not (the step S18). The threshold Dt_th may be changed suitably in accordance with an input operation performed by the medical care provider on the input operation unit6. For example, Dt_th is 0.2. When it is determined that the calculated dispersion Dt exceeds the threshold Dt_th (YES in the step S18), the processing goes to a step S19. In the step S19, the controller2determines that the pulse data of the patient indicate atrial fibrillation. On the other hand, when it is determined that the calculated dispersion Dt does not exceed the threshold Dt_th (NO in the step S19), the processing goes to the step S20.

Then, in a step S21, the controller2outputs a determination result. For example, when it is determined that the pulse data indicate atrial fibrillation, the controller2may display, on the physiological information display screen10illustrated inFIG. 4, a message that the atrial fibrillation is suspected. On the other hand, when it is determined that the pulse data do not indicate atrial fibrillation, the controller2may display, on the physiological information display screen, a message that the atrial fibrillation is not suspected. Particularly, the determination result may be displayed in the pulse analysis result display region R3in the physiological information display screen10which will be described later.

According to the presently disclosed subject matter, it is possible to provide a detecting device1which can determine whether the pulse data indicate atrial fibrillation or not, based on the pulse rate in addition to the dispersion Da of the peak amplitude values Ap and the dispersion Dt of the peak-to-peak time intervals Tp so that the atrial fibrillation can be detected more accurately. In this respect, according to the background art, it is possible to determine whether the pulse data indicate an arrhythmia or not, but it is not possible to accurately determine whether the pulse data indicate premature ventricular contraction or indicate atrial fibrillation. According to the presently disclosed subject matter, due to the parameter of the pulse rate which is newly added, it is possible to accurately determine that the pulse data indicate atrial fibrillation.

In addition, according to the presently disclosed subject matter, when it is determined that the pulse rate exceeds the threshold PRth, the dispersion Da of the peak amplitude values Ap exceeds the threshold Da_th and the dispersion Dt of the peak-to-peak time intervals Tp exceeds the threshold Dt_th (i.e. when all the processings in the steps S16to S18are YES), it is determined that the pulse data indicate atrial fibrillation. Threshold determination can be performed thus on the three parameters individually. Accordingly, the atrial fibrillation can be detected more accurately.

Return toFIG. 2. In a step S22, the controller2visibly displays the calculated pulse rate, and the dispersions Da and Dt in the pulse analysis result display region R3(seeFIG. 4). An example of the processing of the step S22will be described below with reference toFIGS. 3 to 6.

First, as shown inFIG. 4, the physiological information display screen10displayed on the display5can include the ECG waveform display region R1in which the ECG waveform drawn based on the ECG data is displayed, the pulse display region R2in which the plurality of pulses rendered based on the pulse data are displayed, and the pulse analysis result display region R3which is configured as the two-dimensional coordinate system including the vertical axis for the dispersion Da and the horizontal axis for the dispersion Dt.

Next, as shown inFIG. 3, first, the controller2calculates a color of a display point P displayed in the pulse analysis result display region R3based on a calculated pulse rate (step S30). For example, when the pulse rate is lower than 70 (times/minute) (pulse rate<70), the controller2sets the color of the display point P at a first color (e.g. blue). When the pulse rate is not lower than 70 (times/minute) and not higher than 100 (times/minute) (70≤pulse rate≤100), the controller2sets the color of the display point P at a second color (e.g. yellow). When the pulse rate is higher than 100 (times/minute) (pulse rate>100), the controller2sets the color of the display point P at a third color (e.g. red).

In an example shown inFIG. 4, the pulse rate is 105. Accordingly, the controller2sets the color of the display point P at the third color. In addition, in an example ofFIG. 5, the pulse rate is 63. Accordingly, the controller2sets the color of the display point P at the first color. Further, in an example ofFIG. 6, the pulse rate is 73. Accordingly, the controller2sets the color of the display point P at the second color.

Next, the controller2determines coordinates of the display point P in the pulse analysis result display region R3based on the calculated dispersions Da and Dt (step S31). For example, in an example illustrated inFIG. 4, Da=0.3 and Dt=0.21. Accordingly, the controller2sets the coordinates of the display point P at (0.21, 0.3). In an example illustrated inFIG. 5, Da=0.01 and Dt=0.02. Accordingly, the controller2sets the coordinates of the display point P at (0.02, 0.01). Further, in an example illustrated inFIG. 6, Da=0.19 and Dt=0.11. Accordingly, the controller2sets the coordinates of the display point P at (0.11, 0.19). Then, the controller2displays the display point P in the pulse analysis result display region R3(step S32).

According to the presently disclosed subject matter, the dispersion Da of the peak amplitude values Ap and the dispersion Dt of the peak-to-peak time intervals Tp are visibly displayed (visualized) as one point on the two-dimensional coordinate system. Further, the color of the display point P displayed on the two-dimensional coordinate system is determined based on the pulse rate. Thus, the medical care provider can intuitively confirm whether the determination result executed by the detecting device1is correct or not.

Incidentally, the pulse analysis result display region R3may be visibly displayed as a three-dimensional coordinate system. In this case, the pulse analysis result display region R3is configured as a three-dimensional coordinate system (three-dimensional coordinate space) including a first axis for the pulse rate, a second axis for the dispersion Da, and a third axis for the dispersion Dt. Further, the controller2visibly displays the calculated pulse rate and the calculated dispersions Da and Dt as one point on the three-dimensional coordinate system (pulse analysis result display region R3). Particularly, the controller2determines coordinates of the display point P to be displayed in the pulse analysis result display region R3based on the calculated pulse rate and the calculated dispersions Da and Dt. Thus, the calculated pulse rate and the calculated dispersions Da and Dt are visibly displayed as one point on the three-dimensional coordinate system. Accordingly, the medical care provider can more accurately confirm whether the determination result executed by the detecting device1is correct or not. When the pulse analysis result display region R3is configured as the three-dimensional coordinate system, the pulse analysis result display region R3may be displayed in the physiological information display screen10or may be displayed in a window screen provided separately from the physiological information display screen10.

In addition, in order to implement the detecting device1according to the presently disclosed subject matter by software, the atrial fibrillation detecting program may be incorporated into the storage3or the ROM in advance. In addition, the atrial fibrillation detecting program may be stored into a computer-readable storage medium such as a magnetic disk (such as an HDD or a floppy disk), an optical disk (such as a CD-ROM, a DVD-ROM or a Blu-ray disk), a magneto-optical disk (such as an MO), or a flash memory (such as an SD card, a USB memory or an SSD). In this case, the atrial fibrillation detecting program stored in the storage medium is read by a disk drive etc. provided in the detecting device1. Thus, the atrial fibrillation detecting program is incorporated into the storage3. The program incorporated into the storage3is loaded onto the RAM, and the processor executes the program loaded onto the RAM. Thus, the atrial fibrillation detecting method illustrated inFIG. 2can be executed.

In addition, the atrial fibrillation detecting program may be downloaded from a computer on the communication network through the network interface4. Also in this case, the downloaded program is incorporated into the storage3in a similar manner or the same manner.

Although the presently disclosed subject matter has been described above, the technical scope of the present disclosure should not be interpreted limitedly to the description of the presently disclosed subject matter. The presently disclosed subject matter is merely exemplified. It should be understood by those skilled in the art that various changes may be made on the presently disclosed subject matter within the scope of the present disclosure stated in Claims. The technical scope of the present disclosure should be defined based on the scope of the present disclosure stated in the Claims and an equivalent scope thereto.

In addition, in the presently disclosed subject matter, the peak amplitude value Ap and the peak-to-peak time interval Tp have been described as the example of the pulse amplitude index and the example of the pulse interval index respectively. However, the pulse interval index and the pulse amplitude index should not be limited to the peak-to-peak time interval Tp and the peak amplitude value Ap respectively.

For example, in the presently disclosed subject matter, the following indices may be used as the pulse interval index.A time interval between a time point when a pulse rises and a time point when an incisure of the pulse is generatedA time interval between a time point when an incisure of a pulse is generated and a time point when a next pulse risesA time interval between a time point when a pulse rises and a time point when a next pulse rises

For example, in the presently disclosed subject matter, the following indices may be used as examples of the pulse amplitude index.An area of a pulse between a time point when the pulse rises and a time point when a next pulse risesAn area of a pulse between a time point when the pulse rises and a time point when an incisure of the pulse is generated