A wearable device for acquiring multiple electrocardiogram lead signals

Abstract

The present invention relates to a wearable device for acquiring multiple electrocardiogram lead signals, and more particularly to a wearable device as an individually wearable multiple electrocardiogram measuring device (measurement sensor) that is convenient to carry, can be easily used regardless of time and place, and is configured to acquire six electrocardiogram lead signals by two limb lead signals measured simultaneously.

Description

[Technical Field]

[0001] The present invention relates to a wearable device for acquiring multiple electrocardiogram lead signals, and more particularly to a wearable device as an individually wearable multiple electrocardiogram measuring device (measurement sensor) that is portable, can be easily used regardless of time and place, and is configured to acquire six electrocardiogram lead signals through two simultaneously measured limb lead signals.

[0002] The present invention, as an apparatus for measuring multiple electrocardiograms, can be classified according to the International Patent Classification (IPC) in class A61B 5 / 04 for detecting, measuring or recording bioelectric signals of the body or parts thereof. [Background technology]

[0003] Electrocardiographs provide a waveform of electrical signals, or electrocardiograms, that can be easily obtained and contain very useful information for analyzing the condition of a patient's heart.

[0004] In other words, electrocardiographs are useful devices that can conveniently diagnose a patient's cardiac condition. Electrocardiographs can be classified into various types depending on their intended use. To obtain as much information as possible, hospital-use electrocardiographs typically use 12-channel electrocardiographs with 10 wet electrodes. Holter recorders and event recorders, which can be used by users while ambulatory, have the following essential features: they are small, battery-powered, have a memory device for storing measured data, and are equipped with a communication device for transmitting data.

[0005] On the other hand, an event recorder is carried by the user and allows them to instantly measure their own ECG if they sense any abnormalities in their heart. For this reason, the event recorder is small and does not have a cable for connecting electrodes, but has dry electrodes on its surface. Conventional event recorders are mainly one-channel, or one-lead, electrocardiographs that measure one ECG signal by contacting two electrodes with each hand.

[0006] The electrocardiogram measuring device pursued by the present invention must provide an electrocardiogram measuring device that is convenient for individuals to use, accurate, and comprehensive, and must be small and easy to carry. For convenient individual use, the device must transmit data via wireless communication. Also, the device must be battery-powered.

[0007] To provide an accurate and comprehensive electrocardiogram measurement device, the present invention acquires two simultaneously measured limb leads. As described below, the present invention can calculate and provide four leads from two simultaneously measured limb leads. Typically, in the context of electrocardiograms, a "channel" and a "lead" are used interchangeably and refer to one electrocardiogram signal or voltage. The term "simultaneously" should be used very carefully in the context of electrocardiograms. Specifically, if lead I voltage is sampled at a predetermined sampling period while lead II is sampled, the sampling of lead II can be considered simultaneous only if it is performed within less than half the sampling period from the sampling of lead I. Care should also be taken with the use of the word "measurement." The word "measurement" should be used only when an actual physical quantity is measured. In digital measurement, one measurement essentially means one AD conversion. As described below, in an electrocardiogram measurement, if lead I and lead III are measured, lead II can be calculated using Kirchhoff's voltage law. In this case, it would be more accurate to say that Lead II was "calculated," and saying it was "measured" would cause confusion.

[0008] One of the most difficult problems in ECG measurement is to remove power line interference from ECG signals. A well-known method to remove power line interference is the Driven Right Leg (DRL) method.

[0009] Recently, electrocardiographs mounted on smartwatches have become very useful. However, the electrocardiographs mounted on smartwatches only provide electrocardiogram signals between the hands, i.e., lead I signals, which is problematic in that the medical information they provide is insufficient. Therefore, there is a need for a device that can provide a greater number of electrocardiogram signals. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention was conceived in response to the above-mentioned problems and needs, and aims to provide an electrocardiogram device that uses a watch equipped with an electrocardiograph to acquire two limb lead signals measured simultaneously. Measuring two limb leads simultaneously is extremely important medically because sequentially measuring two leads is time-consuming and inconvenient. Furthermore, two limb leads measured at different times may not correlate with each other, which can confuse accurate and detailed arrhythmia discrimination. Most importantly, as will be described later, two limb lead signals must be measured simultaneously in order to calculate four additional limb leads to acquire a total of six limb leads.

[0011] The electrocardiograph installed in the smartwatch measures lead I signals, so to obtain a total of six limb leads as described below, one of lead II and lead III must be measured and obtained. Furthermore, the method for measuring one of lead II and lead III must be convenient for the user. Furthermore, the structure of the device and the electrode arrangement used to measure one of lead II and lead III must be convenient for the user.

[0012] SUMMARY OF THE INVENTION The present invention addresses the above problems and meets the needs by employing an electrocardiograph located on a watch band.

[0013] However, the electrocardiograph mounted on the wristband used in the present invention must communicate wirelessly with the electrocardiograph mounted on the watch in order to transmit the measured electrocardiogram signal to the electrocardiograph mounted on the watch. However, since wireless communication inevitably generates a time delay, the time delay must be compensated for in order to obtain two electrocardiogram signals measured simultaneously. Therefore, there is a problem in that it is necessary to know the time delay value generated by wireless communication.

[0014] Generally, a portable measuring device uses a battery and requires a mechanical power switch to control the battery power consumption, but the mechanical power switch increases the volume and area of ​​the portable measuring device, limits miniaturization, and increases the possibility of malfunction.

[0015] The present invention was devised in response to the above-mentioned problems and needs, and provides an electrocardiogram device that acquires two limb leads measured simultaneously using a watch equipped with an electrocardiograph, and uses an additional mechanical switch depending on the embodiment, or if necessary. [Means for solving the problem]

[0016] To achieve the above-mentioned objectives, the wearable device of the present invention is a non-contact electrocardiogram measuring device that includes a watch worn on one wrist by a user; one band connected to the watch; a first electrocardiograph connected to one of the bands and positioned opposite the bottom of the watch; and a second electrocardiograph included in the watch; wherein the first electrocardiograph includes a first electrode positioned on the inner surface of the band so as to contact the one wrist of the user, and a second electrode positioned on the outer surface of the band so as to be able to contact the user's left knee or left ankle, and the second electrocardiograph may include a third electrode positioned on the bottom of the watch so as to contact the one wrist of the user, and a fourth electrode that can be able to contact the user's other hand.

[0017] In addition, the first electrocardiograph measures a first electrocardiogram lead signal induced between the first electrode and the second electrode and transmits the measured first electrocardiogram lead signal to the second electrocardiograph via wireless communication means, and the second electrocardiograph measures a second electrocardiogram lead signal through the third electrode and the fourth electrode and receives the first electrocardiogram lead signal via wireless communication means, and compensates for a time delay occurring in the wireless communication process in the received first electrocardiogram lead signal so that the first electrocardiogram lead signal and the second electrocardiogram lead signal become two electrocardiogram lead signals sampled at the same time.

[0018] In addition, the wearable device can calculate four additional electrocardiogram lead signals using the two electrocardiogram lead signals sampled at the same time to obtain six limb lead signals including lead I, lead II, lead III, lead aVR, lead aVL, and lead aVF.

[0019] The first electrocardiograph also includes a microcontroller for controlling the first electrocardiograph, and when the first electrocardiograph is not measuring electrocardiogram lead signals, the microcontroller operates in a sleep mode and turns off the amplifier, AD converter, and wireless communication means included in the first electrocardiograph, and when the microcontroller is changed to an active mode, it turns on the amplifier, AD converter, and wireless communication means, amplifies the first electrocardiogram lead signals, converts them into AD signals, and performs wireless communication.

[0020] In addition, the first electrocardiograph includes a current sensor to which power is supplied, and the current sensor allows a current to flow through the user's body when the first electrode contacts one of the user's wrists and the second electrode contacts the user's left knee or left ankle, and generates an output signal when it senses the current. The microcontroller can be changed from a sleep mode to an activated mode when it receives the output signal from the current sensor.

[0021] Furthermore, the wearable device according to the present invention determines the time delay value using the following steps (1) to (4).

[0022] (1) One output signal from one signal generator is commonly applied to the first electrocardiograph and the second electrocardiograph.

[0023] (2) The first electrocardiograph and the second electrocardiograph measure the output signals.

[0024] (3) The first electrocardiograph transmits the measured signal via wireless communication means, and the second electrocardiograph receives the transmitted signal.

[0025] (4) Comparing the waveforms of the signal measured by the second electrocardiograph with the waveforms of the signal received by the second electrocardiograph.

[0026] In addition, the bands may be formed such that one band is longer than the other band with respect to the watch in order to position the first electrocardiograph.

[0027] The wireless communication means may be implemented in a Bluetooth® low energy format.

[0028] Furthermore, a method of acquiring multiple electrocardiogram leads according to the present invention using an electrocardiogram built into a watch worn on one wrist and an electrocardiogram attached to a band of the watch includes the steps of: contacting a first electrode of the electrocardiogram attached to the band with the wristband and a second electrode with the left foot or ankle; switching a microcontroller built into the electrocardiogram attached to the band to an active mode; turning on the amplifier, the AD converter, and the wireless communication means when the microcontroller is switched to the active mode; amplifying the electrocardiogram leads between the first electrode and the second electrode; and a step of converting a digital signal into a digital signal; a step of transmitting the first electrocardiogram lead data converted into a digital signal to the electrocardiograph built in the watch via the wireless communication means; a step of receiving the transmitted first electrocardiogram lead data via the wireless communication means by the electrocardiograph built in the watch; and a step of compensating for a time delay occurring during the wireless communication process, etc., in the received first electrocardiogram lead data so that the second electrocardiogram lead data measured via electrodes attached to the watch and the first electrocardiogram lead data become two electrocardiogram lead data sets sampled at the same time.

[0029] In addition, the method for acquiring a plurality of electrocardiogram lead signals may further include a step in which a microcontroller built into the electrocardiograph attached to the band performs electrocardiogram measurement for a predetermined time, and then checks whether a current is flowing through the current sensor to determine whether to terminate the electrocardiogram measurement.

[0030] In other words, in one embodiment of the present invention, a wearable device is provided that includes one watch electrocardiograph that measures lead I; and one downward lead electrocardiograph that measures one of leads II or III depending on the placement position.

[0031] On the other hand, the present invention is characterized in that the difference between the sampling points of the two electrocardiogram lead signals is smaller than the sampling period in order to obtain the two electrocardiogram lead signals sampled in the same time band.

[0032] Meanwhile, in order to achieve the above object, the present invention provides a wearable device including one watch electrocardiograph installed in one watch body and measuring lead I; and one downward lead electrocardiograph that measures one of lead II or lead III depending on the installation position; wherein the watch electrocardiograph wirelessly transmits a command to start electrocardiogram measurement (electrocardiogram measurement start command) to the one downward lead electrocardiograph, and the watch electrocardiograph measures lead I, and the one downward lead electrocardiograph that has wirelessly received the electrocardiogram measurement start command measures one of lead II or lead III, and A wearable device is presented, characterized in that when one of the measured leads II or III is wirelessly transmitted from one downward lead electrocardiograph to the watch electrocardiograph, the watch electrocardiograph wirelessly receives one of the transmitted leads II or III to obtain two electrocardiogram lead signals measured in the same time band, and additionally calculates four electrocardiogram lead signals using the two electrocardiogram lead signals measured in the same time band to obtain six limb lead signals consisting of leads I, II, III, aVR, aVL, and aVF.

[0033] In this case, one downward lead electrocardiograph for measuring one of Lead II or Lead III is connected to one band connected to one watch body and is positioned opposite the bottom surface of the watch body; it may include one electrode arranged on the inner surface of the band so as to contact one of the user's wrists, and one electrode arranged on the outer surface of the band so as to be able to contact the user's left knee or left ankle.

[0034] In one embodiment, one downward lead electrocardiograph for measuring one of Lead II or Lead III may be in the form of a ring worn on one finger.

[0035] In one embodiment, a single downward lead electrocardiograph measuring one of the leads II or III may include an electrode in the form of a patch or chest band that is placed in contact with the chest.

[0036] On the other hand, in the present invention, the two electrocardiogram lead signals measured in the same time band are characterized by having the same frequency response characteristics.

[0037] Meanwhile, in the present invention, the two electrocardiogram lead signals measured in the same time band have the same gain characteristics.

[0038] Meanwhile, in the present invention, the two electrocardiogram lead signals measured in the same time band are characterized in that the maximum amplitude error is within ±5%.

[0039] Meanwhile, the present invention is characterized in that the two electrocardiogram lead signals measured in the same time band are sampled at the same sampling rate.

[0040] The wireless communication method between the watch electrocardiograph and the single downward lead electrocardiograph is Bluetooth low energy.

[0041] Meanwhile, the one downward lead electrocardiograph samples the electrocardiogram lead signal during one connection interval after the Bluetooth Low Energy connection is established, and transmits the sampled data during one connection event according to the sampling.

[0042] At this time, the connection interval is an integer multiple of a sampling period when one downward lead electrocardiograph samples one electrocardiogram lead signal.

[0043] Meanwhile, in the present invention, the watch electrocardiograph and the single downward lead electrocardiograph sample their respective electrocardiogram lead signals at the same time by sampling each of the electrocardiogram lead signals after the same time has elapsed since the connection event.

[0044] Meanwhile, the present invention is characterized in that the operation of additionally calculating the four electrocardiogram lead signals and the operation of displaying the six limb lead signals are performed by a smartphone.

[0045] Meanwhile, in the present invention, the electrocardiogram measurement start command is generated by one electrocardiograph after a photoelectric volume pulse wave meter mounted on the one electrocardiograph detects abnormal cardiac activity and generates an alarm.

[0046] Meanwhile, in the present invention, the ECG measurement start command is generated by the downward lead ECG or watch ECG after a current sensor generates an output when it detects that the user has brought the user's body into contact with two electrodes of the downward lead ECG to measure the ECG. [Effects of the Invention]

[0047] The wearable device of the present invention is highly useful in healthcare because it is portable, can be used easily at any time and place, and can obtain six electrocardiogram lead signals. [Brief explanation of the drawings]

[0048] [Figure 1] 1 is a perspective view of a wearable device according to the present invention in one direction. [Figure 2] FIG. 2 is a perspective view of the wearable device according to the present invention in another direction. [Figure 3] FIG. 2 is a block diagram of a second electrocardiograph according to the present invention. [Figure 4] 1 is a perspective view of a ring-shaped electrocardiograph used in the present invention. [Figure 5] 1 is a diagram showing a patch electrocardiograph used in the present invention attached to a user's chest. [Figure 6] 1 is a diagram showing a chest band electrocardiograph used in the present invention worn on a user's chest. [Figure 7] 1 is a diagram illustrating the operation of sampling electrocardiogram lead signals and transmitting and receiving the sampled data when two electrocardiographs are connected via Bluetooth Low Energy according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0049] In its best mode, the present invention provides a wearable device including one watch electrocardiograph attached to one watch body and measuring Lead I; and one downward-lead electrocardiograph measuring one of Lead II or Lead III depending on the location where the watch electrocardiograph is attached, wherein the watch electrocardiograph wirelessly transmits a command to start electrocardiogram measurement to the one downward-lead electrocardiograph, and the watch electrocardiograph measures Lead I. The one downward-lead electrocardiograph that has wirelessly received the command to start electrocardiogram measurement measures one of Lead II or Lead III and measures the one downward-lead electrocardiograph. When the electrocardiograph wirelessly transmits one of the measured Lead II or Lead III to the watch electrocardiograph, the watch electrocardiograph wirelessly receives one of the transmitted Lead II or Lead III to obtain two electrocardiogram lead signals measured in the same time band, and calculates four additional electrocardiogram lead signals using the two electrocardiogram lead signals measured in the same time band to obtain six limb lead signals consisting of Lead I, Lead II, Lead III, Lead aVR, Lead aVL, and Lead aVF.

[0050] Embodiment The wearable device for acquiring multiple electrocardiogram lead signals according to the present invention will now be described in detail with reference to the accompanying drawings. The drawings are provided as examples to fully convey the concept of the present invention to those skilled in the art. Therefore, the present invention is not limited to the drawings shown below and may be embodied in other forms. In addition, the same reference numerals refer to the same elements throughout the specification.

[0051] Unless otherwise defined, the technical and scientific terms used herein have the meanings commonly understood by those having ordinary knowledge in the technical field to which the present invention belongs, and in the following description and accompanying drawings, descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention will be omitted.

[0052] In explaining the present invention, once two limb lead signals are measured, four additional leads can be calculated and obtained as described below. The above measurement method is the most convenient method provided by the present invention to obtain six ECG lead signals. The principle of the present invention is as follows.

[0053] For example, the traditional 12-lead ECG is described in [ANSI / AAMI / IEC 60601-2-25:2011, Medical electrical equipment - part 2-25: Particular requirements for the basic safety and essential performance of electrocardiographs]. In the traditional 12-lead ECG, the three limb leads are defined as follows: Lead I = LA-RA, Lead II = LL-RA, and Lead III = LL-LA. In the above formula, RA, LA, and LL represent the voltages of the right arm, left arm, and left leg, respectively, or the torso areas close to these limbs. From the above relationship, one limb lead can be calculated from the other two limb leads. For example, Lead III = Lead II - Lead I. The three augmented limb leads are defined as follows: aVR=RA-(LA+LL) / 2, aVL=LA-(RA+LL) / 2, aVF=LL-(RA+LA) / 2. Therefore, the three augmented limb leads can be calculated from two limb leads. For example, aVR=-(I+II) / 2. Therefore, once two limb leads are measured, the remaining four leads can be calculated.

[0054] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0055] FIG. 1 is a perspective view of a wearable device according to the present invention in one direction, and FIG. 2 is a perspective view of a wearable device according to the present invention in another direction. The structure of the wearable device according to the present invention and the arrangement of electrodes used therein will be described with reference to FIGS. 1 and 2. The wearable device according to the present invention includes a watch 200 worn on one wrist by a user, a band 300 coupled to the watch 200, a first electrocardiograph 100 coupled to one band 300 and positioned at a position 370 facing the bottom of the watch 200, and a second electrocardiograph 200 included in the watch 200. In the present invention, in order to position the first electrocardiograph 100 at a position 370 facing the bottom of the watch 200, the band 300 needs to be longer than the band 300' (FIG. 1). In the present invention, the watch may include other elements 250 and 260 unrelated to the second electrocardiograph. However, in describing the present invention using FIGS. 1 and 2, the watch and the second electrocardiograph are denoted by the same reference numeral 200 for convenience.

[0056] In Fig. 1, the first electrocardiograph 100 includes a first electrode 110 disposed on an inner surface 350 of the band 300, and the second electrocardiograph 200 includes a fourth electrode 220 that can contact the hand wearing the watch 200 and the other hand. In Fig. 2, the first electrocardiograph 100 includes a second electrode 120 disposed on an outer surface 360 ​​of the band 300, and the second electrocardiograph 200 includes a third electrode 210 that contacts the wrist wearing the watch 200.

[0057] In this embodiment, the first electrocardiograph 100 measures a first electrocardiogram lead signal induced between the first electrode 110 and the second electrode 120. When the watch 200 is worn on the left wrist, the first electrocardiogram lead signal measured when the second electrode 120 is in contact with the user's left knee or left ankle is Lead III.

[0058] In this embodiment, the second electrocardiograph 200 measures a second electrocardiogram lead signal induced between the third electrode 210 and the fourth electrode 220. When the watch 200 is worn on the left wrist, the second electrocardiogram lead signal measured when the fourth electrode 220 is in contact with a finger of the user's right hand is Lead I.

[0059] In the present invention, the first electrocardiograph 100 and the second electrocardiograph 200 are separate and independent devices and are not connected to each other by wires. Therefore, in the present invention, the first electrocardiograph 100 and the second electrocardiograph 200 are connected to each other only by wireless communication.

[0060] In this embodiment, the first electrocardiograph 100 transmits the measured first electrocardiogram lead signals to the second electrocardiograph 200 via wireless communication means. The second electrocardiograph 200 receives the first electrocardiogram lead signals via wireless communication means.

[0061] In the present invention, the first electrocardiograph 100 and the second electrocardiograph 200 are each supplied with power from a separate battery. One thing to note about FIGS. 1 and 2 is that the first electrocardiograph 100 does not include any mechanical switch. As will be further explained in FIG. 3, when a current flows between the first electrode 110 and the second electrode 120, the microcontroller built into the first electrocardiograph 100 switches to active mode and powers on the internal devices of the first electrocardiograph 100. When electrocardiogram measurement is not being performed, the microcontroller powers off the internal devices of the first electrocardiograph 100 and enters sleep mode to prevent power consumption of the internal battery of the first electrocardiograph 100.

[0062] 3 is a block diagram showing the internal structure of the first electrocardiograph 100. Electrocardiogram lead signals are input to the first electrode 110 and the second electrode 120. An amplifier 310 amplifies the input electrocardiogram lead signals. An AD converter 320 converts the input analog signals into digital signals. A microcontroller 330 receives the AD-converted electrocardiogram lead signals and transmits them via a wireless communication means 340 and an antenna 350.

[0063] The current sensor 360 is always powered by a built-in battery. When the left knee or left foot touches the second electrode 120 while the first electrode 110 is in contact with the wrist, the current sensor 360 causes a current to flow between the first electrode 110 and the second electrode 120, causing the microcontroller 330, which is in the sleep mode, to change to the active mode. Then, the microcontroller 330 powers on the wireless communication unit 340 and communicates with the second electrocardiograph 200 to determine whether the second electrocardiograph 200 requires electrocardiogram measurement. If the second electrocardiograph 200 requires electrocardiogram measurement, the microcontroller 330 powers on the amplifier 310 and the AD converter 320 to perform electrocardiogram measurement.

[0064] After the ECG measurement is performed for a predetermined period of time, the state of the current sensor 360 is checked to determine whether to terminate the ECG measurement. Typically, ECG determination takes approximately 30 seconds. The user can check whether 30 seconds have elapsed through the watch display and discontinue contact with the ECG electrodes. However, if the user requires a measurement that lasts longer than 30 seconds, the user can continue to contact the electrodes. If the current sensor 360 does not detect current flow, the microcontroller 330 powers off the amplifier 310 and the AD converter 320, and the microcontroller 330 enters sleep mode. While the AD converter 320 has been described above as a separate device from the microcontroller 330, the AD converter 320 may also be incorporated within the microcontroller 330.

[0065] The second electrocardiograph 200 receives the first electrocardiogram lead signal transmitted from the first electrocardiograph 100 via wireless communication. In this case, a time delay of a predetermined time occurs due to the wireless communication protocol. When calculating a third electrocardiogram lead signal by applying Kirchhoff's law using two electrocardiogram lead signals, the two electrocardiogram lead signals must be measured at the same time. Here, "two signals measured at the same time" means that the difference between the two sampling points must be shorter than the sampling period for converting an analog signal into a digital signal. Typically, the sampling period for measuring an electrocardiogram signal is about 3 ms. Therefore, if a time delay of about 1 ms or more occurs in wireless communication, the time delay must be compensated.

[0066] The wireless communication method suitable for the present invention is the Bluetooth Low Energy (BLE) method, which has short-distance and low-power characteristics. In order to know the time delay occurring in the BLE method, the following method can be used.

[0067] (1) One output signal output from one signal generator is commonly applied to the first electrocardiograph and the second electrocardiograph.

[0068] (2) The first electrocardiograph and the second electrocardiograph measure the output signals.

[0069] (3) The first electrocardiograph transmits the measured signal via wireless communication means, and the second electrocardiograph receives the transmitted signal.

[0070] (4) Comparing the waveforms of the signal measured by the second electrocardiograph with the waveforms of the signal received by the second electrocardiograph.

[0071] The waveform of the one output signal output from the one signal generator may be, for example, a triangular wave. In order to accurately determine the time delay, the first electrocardiograph and the second electrocardiograph may measure the output signals using a sampling period shorter than the sampling period used to measure the electrocardiogram.

[0072] The wearable device of the present invention is highly useful in healthcare because it is portable, can be easily used anywhere and at any time, and can obtain six electrocardiogram lead signals.

[0073] As mentioned above, the first embodiment has been described, in which six limb lead signals are obtained using two electrocardiographs, each measuring one electrocardiogram lead. A new embodiment will now be described. To describe the new embodiment and the first embodiment as a unified concept, more appropriate terms and names may be used instead of the terms and names used in the first embodiment.

[0074] In the first embodiment, the second electrocardiograph 200 is installed in the watch body. This was previously described using FIG. 1. Also, as previously mentioned, the second electrocardiogram lead signal measured by the second electrocardiograph 200 is the electrocardiogram lead signal between both hands, i.e., lead I. Also, previously, the watch and the second electrocardiograph 200 were denoted by the same reference numeral 200 for convenience. Therefore, for convenience, the name "watch electrocardiograph 200" may be used instead of the name "second electrocardiograph 200." The watch electrocardiograph 200 measures lead I.

[0075] In the first embodiment, it was described that when the watch is worn on the left wrist, the first electrocardiograph measures lead III. On the other hand, when the watch is worn on the right wrist, the first electrocardiograph measures lead II. In the technical field or literature on electrocardiograms, leads II, III, and aVF are classified as inferior leads. Therefore, the first electrocardiograph described in the first embodiment may be called an inferior lead electrocardiograph. Using this name, the first embodiment can be expressed as follows. That is, a wearable device that obtains six limb lead signals according to the present invention can be described as an electrocardiogram measurement device (measurement sensor) as follows:

[0076] A wearable device including one watch electrocardiograph (200) installed in one watch body and measuring lead I; and one downward lead electrocardiograph (100) measuring one of lead II or lead III depending on the installation position; wherein the watch electrocardiograph (200) wirelessly transmits a command to start electrocardiogram measurement to the one downward lead electrocardiograph (100), the watch electrocardiograph (200) measures lead I, and the one downward lead electrocardiograph (100) that has wirelessly received the command to start electrocardiogram measurement measures one of lead II or lead III and returns to the one downward lead electrocardiograph (100). When the electrocardiograph (100) wirelessly transmits one of the measured leads II or III to the watch electrocardiograph (200), the watch electrocardiograph (200) wirelessly receives one of the transmitted leads II or III to obtain two electrocardiogram lead signals measured in the same time band, and uses the two electrocardiogram lead signals measured in the same time band to additionally calculate four electrocardiogram lead signals to obtain six limb lead signals consisting of leads I, II, III, aVR, aVL, and aVF.

[0077] With the present invention described above, the first electrocardiograph 100 of the first embodiment can be described as follows.

[0078] One downward lead electrocardiograph 100 (first electrocardiograph) that measures one of Lead II or Lead III is connected to one band 300 that is connected to one watch body 200, is positioned opposite the bottom surface of the watch body, and includes one electrode 110 (first electrode) that is arranged on the inner surface 350 of the band so as to contact one of the user's wrists, and one electrode 120 (second electrode) that is arranged on the outer surface 360 ​​of the band so as to be able to contact the user's left knee or left ankle.

[0079] A second embodiment will now be described. In the first embodiment, the downward-lead electrocardiograph 100 is mounted on a band 300 attached to a watch, but this is not a requirement. In the second embodiment, the downward-lead electrocardiograph 100 is in the form of a ring 400 worn on one finger. In the second embodiment, the downward-lead electrocardiograph 100 also measures one of Lead II or Lead III. In the second embodiment, the watch electrocardiograph 200 also measures Lead I, as in the first embodiment.

[0080] FIG. 4 shows a ring-shaped downward-lead electrocardiograph 400. The ring-shaped downward-lead electrocardiograph 400 includes at least one electrode 410 on the inside of the ring and one electrode 420 on the outside of the lower side of the ring. When the ring-shaped downward-lead electrocardiograph 400 is worn on the left hand and the outer electrode 420 is in contact with the left foot, the ring-shaped downward-lead electrocardiograph 400 measures lead III. When the ring-shaped downward-lead electrocardiograph 400 is worn on the right hand and the outer electrode 420 is in contact with the left foot, the ring-shaped downward-lead electrocardiograph 400 measures lead II. Although FIG. 4 shows at least one electrode 410 on the inside of the ring as being located away from the outer electrode 420 for convenience, it may also be located closer to the outer electrode 420. The downward-lead electrocardiograph 400 may also include a driven right leg electrode 430.

[0081] A third embodiment will now be described. In the third embodiment, the downward-lead electrocardiograph is a patch-type downward-lead electrocardiograph (patch electrocardiograph) 500 or a chest-band-type downward-lead electrocardiograph (chest-band electrocardiograph) 600. In the third embodiment, the patch- or chest-band-type downward-lead electrocardiograph 500, 600 is contacted to the chest to measure analogous lead II. Original lead II is an electrocardiogram signal induced between the right hand and left foot. However, when the electrocardiograph is attached to an appropriate chest location, an electrocardiogram signal nearly identical to lead II can be obtained, and this signal is called analogous lead II. Therefore, to measure analogous lead II, it is necessary to carefully select the contact location of the patch- or chest-band-type downward-lead electrocardiograph 500, 600. In the third embodiment, the watch electrocardiograph 200 also measures lead I, as in the first embodiment.

[0082] FIG. 5 shows a patch electrocardiograph 500 attached to the chest. The patch electrocardiograph 500 can be attached to the chest for approximately two weeks to continue measuring an electrocardiogram. FIG. 6 shows a chest-band electrocardiograph 600 worn on the chest. The chest-band electrocardiograph 600 is attached to an elastic band 610. The chest-band electrocardiograph 600 uses dry electrodes, making it easy to wear and suitable for long-term use. A conventional chest-band electrocardiograph 600 can also obtain electrocardiogram signals other than analogous lead II. However, the chest-band electrocardiograph 600 used in the present invention obtains analogous lead II and can use it to calculate other leads. The patch electrocardiograph 500 or chest-band electrocardiograph 600 can also measure one or two chest leads, such as V1, V2, V3, V4, V5, and V6, as needed.

[0083] The second and third embodiments have been described above. The content of the first embodiment may also be applied to the second and third embodiments. Furthermore, the content that will be described below may also be applied to all embodiments. In the present invention, measuring in the same time band means that the start and end points of the measurement are the same. Depending on the context, one measurement may mean one AD conversion, i.e., one sampling, of an ECG lead signal.

[0084] One of the objectives of the present invention is to calculate four additional electrocardiogram lead signals using two electrocardiogram lead signals measured by two electrocardiogram monitors (a watch electrocardiogram monitor and a downward-lead electrocardiogram monitor) that communicate only wirelessly. The following describes the conditions necessary to achieve the above objective, as well as an apparatus and method that satisfy these conditions.

[0085] First, let us summarize the equations for the six commonly known limb leads of an electrocardiogram. Equations 1 to 6 below are the equations for the six limb leads among the equations for the standard 12 leads described in the international medical equipment standard ANSI / AAMI / IEC 60601-2-25:2011, Medical electrical equipment - part 2-25: Particular requirements for the basic safety and essential performance of electrocardiographs. RA, LA, and LL are the voltages measured by the electrocardiograph at the right arm, left arm, left leg, or the torso area close to these limbs, respectively.

[0086]

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[0092] The present invention is highly original in that it uses two ECG lead signals measured by two electrocardiographs to calculate four additional ECG lead signals, as will be described below. The principles of the present invention, which will be described later, have already been briefly described in the section describing FIG. 1.

[0093] In the present invention, when two electrocardiographs measure lead I and lead II, the four leads are calculated using the following formula:

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[0098] The present invention is highly original in that it uses Equations 7 to 10. Thomson et al. disclosed Equations 8 to 10 (US Patent Application Publication, Pub. No.: US2015 / 0018660 A1, Pub. Date: January 15, 2015, Appl. No.: 14 / 328,962, Claim 28). However, Thomson et al. measured three voltages, RA, LA, and LL, to utilize the three equations. In contrast, the present invention measures two ECG lead signals, i.e., ECG voltages. Therefore, the present invention is more effective than Thomson et al. Thomson et al. also uses Equation 3, i.e., III = LL - LA, without using Equation 7. (As mentioned above, Thomson et al. only used Equations 8 to 10.) Furthermore, the present invention discloses Equations 11 to 14 in addition to Equations 7 to 10. Therefore, the present invention differs from Thomson et al. Also, while Thomson et al. use one electrocardiograph, the present invention uses two electrocardiographs connected only wirelessly. The present invention is more effective and original because it measures two leads using two electrocardiographs connected only wirelessly to obtain six limb leads.

[0099] In the present invention, when two electrocardiographs measure lead I and lead III, the four leads are calculated using the following formula:

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[0104] There are several points to be noted in order to realize the unique present invention. Each term in Equation 11 can be expressed as a function of time as follows:

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[0106] Equation 15 above means that to determine another lead from two measured leads, the two measured leads must be sampled at the same time. In Equation 15, T represents the sampling period and n represents the sampling number. Assume that the command to start ECG measurement occurs at t=0. Then, to represents the time elapsed until the first sampling (n=0) (t=to) is performed. If the total number of samplings is N+1, NT represents the total measurement time. In one embodiment, if the sampling rate is 300 sps (samples / second), T = 3.333 ms. If measurement is performed for 30 seconds, N = 30 s / 3.333 ms = 9,000.

[0107] Equation 15 indicates that the two ECG lead signals, i.e., Lead I and Lead II, are sampled at the same sampling rate. Therefore, when using this equation in the present invention, the two ECG devices must sample their respective ECG lead signals at the same sampling rate. Of course, if the sampling rates are different, interpolation can be used to convert them to the same sampling rate. However, using the same sampling rate is much more effective.

[0108] Equation 15 is an expression for a preferred case, and in a practical situation it can be expressed as follows:

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[0110] Here, del is a time delay. The time delay del occurs because it is difficult to accurately determine the time of transmission and reception during the wireless communication process performed by the two electrocardiographs. Also, del may occur due to differences in the operation of the wireless communication means 340, microcontroller 330, and AD converter 320 of the two electrocardiographs. The time delay del ultimately refers to the difference in the sampling points of the two electrocardiogram lead signals, i.e., the time delay. The time delay that occurs during the wireless communication process may cause a difference in the sampling points.

[0111] In order to use Equations 7 to 10 or Equations 11 to 14 in the present invention, the difference del between the sampling times of the two electrocardiogram lead signals must be smaller than the sampling period T. Preferably, the difference del between the sampling times of the two electrocardiogram lead signals must be much smaller than T / 2. The goal of the present invention is to obtain two electrocardiogram lead signals that can use an equation expressed in the form of Equation 15.

[0112] In order to use Equations 7 to 10 or Equations 11 to 14 in the present invention, additional conditions that must be satisfied by the two electrocardiographs used in the present invention or the two electrocardiogram lead signals measured by the two electrocardiographs will be described below.

[0113] The wearable device according to the present invention is a medical device. The two electrocardiographs used to embody the present invention must comply with the medical device certification standard. The applicable international standard is ANSI / AAMI / IEC 60601-2-47:2012, Medical electrical equipment - part 2-47: Particular requirements for the basic safety and essential performance of ambulatory electrocardiographic systems.

[0114] To embody the present invention, the following condition is required: the gains of the two electrocardiographs used in the present invention must be the same. Applying two electrocardiogram lead signals measured using two electrocardiographs with unequal gains to one of the above equations will result in undesirable results. Here, "gain" includes the gain of the amplifier used in the electrocardiograph, and refers to the final gain obtained by performing digital signal processing after AD conversion. The digital signal processing does not have to be performed in the electrocardiograph that performed the AD conversion, but can be performed in another electrocardiograph or a smartphone. Furthermore, "same" means that the magnitude of the difference is smaller than the allowable range. According to the international standard, the accuracy of gain should be such that the maximum amplitude error is within 10%.

[0115] To embody the present invention, the following conditions are necessary: ​​The gain accuracy of the two electrocardiographs used in the present invention must be better than the gain accuracy required by the international standard. For example, the maximum amplitude error must be within ±5%. Otherwise, the lead accuracy calculated when applying Equations 7 to 14 above would result in a maximum amplitude error of 10% or more. To explain this, an example will be given using Table 1.

[0116] Table 1 shows an example of error analysis when calculating aVF using Equation 10.

[0117] [Table 1]

[0118] In the example shown in Table 1, when a test signal of 0.60 mV is applied to Lead I and 1.00 mV to Lead II, the measured values ​​are 0.54 mV for Lead I and 1.10 mV for Lead II. In this case, the measurement accuracy is within the range permitted by the international standard. However, when aVF is calculated using Equation 10 with this measurement, the result is 0.83 mV, which is 119% of the error-free value of 0.70 mV. In this case, an error of 19% occurs, exceeding the 10% allowable range of the standard. If the measurement error allowance for Lead I and Lead II is set to 5%, the aVF calculated by Equation 10 becomes 0.765 mV. In other words, an error of 9% occurs, satisfying the international standard. Therefore, when the present invention is implemented, the measurement accuracy of the two electrocardiographs must be superior to the international standard.

[0119] To implement the present invention, the following condition is required: the frequency response characteristics of the two electrocardiographs used in the present invention must be identical. According to the international standard, the frequency response requirements when testing with a sine wave are as follows: the amplitude response in the frequency range from 0.67 Hz to 40 Hz must be within 140% and 70% of the amplitude response at 5 Hz.

[0120] To realize this invention, the following conditions are necessary: ​​the frequency response characteristics of the two electrocardiographs used in this invention must be better than the requirements of the international standard. The reason for this is the same as the reason for the need for better gain accuracy mentioned above. For example, the amplitude response in the frequency range from 0.67 Hz to 40 Hz must be within 120% and 85% of the amplitude response at 5 Hz.

[0121] The two electrocardiographs used in the present invention are connected to each other only via wireless communication. This is because it would be inconvenient to connect the two electrocardiographs used in the present invention via wires, or because each electrocardiograph manufacturer may manufacture an electrocardiograph that can only measure one electrocardiogram lead. As mentioned above, a suitable wireless communication method for use in the present invention is Bluetooth Low Energy (BLE). Bluetooth Low Energy is suitable for reducing power consumption of the battery built into the wearable device in situations where the amount of data transmitted and received is relatively small and high-speed transmission and reception is not required, as in the present invention.

[0122] FIG. 7 illustrates an embodiment of the present invention in which a watch electrocardiograph 200 and downward lead electrocardiographs 100, 400, 500, and 600 communicate using Bluetooth Low Energy. In FIG. 7, the operation of the watch electrocardiograph 200 is shown at the bottom, and the operation of the downward lead electrocardiographs 100, 400, 500, and 600 is shown at the top over time. In this embodiment, the two electrocardiographs have the same sampling rate, for example, 300 sps, and sample at a period T of 3.33 ms. After a connection between the master and slave is established using Bluetooth Low Energy, a connection event occurs at a predetermined connection interval. Transmission and reception occur during one connection event. In the embodiment of FIG. 7, the downward lead electrocardiographs 100, 400, 500, and 600 perform six samples during a 20 ms connection interval and transmit the six sampled data in one connection event following the sampling. The watch electrocardiograph 200 samples at the same time points as the downward lead electrocardiographs 100, 400, 500, and 600. For example, during a 30 second measurement period, a coupling event occurs every 20 ms.

[0123] To embody the present invention, the following conditions must be met: the downward lead electrocardiographs 100, 400, 500, and 600 must transmit a predetermined number of sampled data sets in a single connection event. Therefore, the sampling and connection events must not overlap in time. It is important to note that in order for the sampling and connection events to not overlap in time, the connection interval must be an exact integer multiple of the sampling period. In the embodiment of FIG. 7, six samples are performed in one electrocardiograph during one connection interval. It is also important to note that the sampling period, T, is the same value regardless of whether a connection event occurs between two consecutive samples.

[0124] It is very important in the present invention that the sampling and the Bluetooth Low Energy connection event do not overlap in time. The fact that the sampling and the connection event do not overlap in time means that the first sampling after the connection event occurs is performed within a time period shorter than the sampling period after the connection event begins. In the present invention, two electrocardiographs are required to sample at the same time. In Bluetooth Low Energy, the master and slave perform a connection event at the same time. Therefore, the watch electrocardiograph 200 and the downward lead electrocardiographs 100, 400, 500, and 600 each sample when the same time has elapsed since the connection event began. As a result, the two electrocardiographs obtain two sampled values ​​sampled at the same time.

[0125] For example, in Figure 7, six pieces of sampled data sampled after one connection event is completed are temporarily stored in memory and then transmitted in the subsequent connection event. An electrocardiograph receiving the transmitted six pieces of sampled data can sequentially substitute the six pieces of sampled data, together with six pieces of sampled data sampled by itself in the same time band, into Equations 7 to 10 or Equations 11 to 14. Thus, for example, 4 leads * 6 samples / lead = 24 samples can be generated.

[0126] The above describes an example of transmitting data measured by the downward lead electrocardiographs 100, 400, 500, and 600 to the watch electrocardiograph 200 in accordance with the present invention. However, the display size of a watch is small, making it difficult to display six electrocardiogram leads. Therefore, the watch electrocardiograph 200 may transmit two electrocardiogram lead data collected by the watch electrocardiograph 200 to a smartphone, which may then calculate four electrocardiogram lead signals and display six electrocardiogram lead signals. Alternatively, the first two electrocardiographs may transmit measured data to a smartphone, which may then calculate four electrocardiogram lead signals and display six electrocardiogram lead signals. In this case, a method similar to that shown in FIG. 7 may also be used.

[0127] The following describes when and why an electrocardiogram measurement start command (a command to start an electrocardiogram measurement) is issued in the present invention. Arrhythmia can be intermittent and asymptomatic. Therefore, a photoplethysmograph (PPG) can be installed in a watch to continuously monitor pulse or cardiac activity. A photoplethysmograph has the advantage of being able to be worn on one hand. When the PPG, which monitors cardiac activity, detects abnormal cardiac activity, i.e., the onset of arrhythmia, the PPG can generate an alarm. The alarm may be in the form of sound, vibration, or light. The user can then measure an electrocardiogram after sensing the alarm. In particular, the present invention can measure two electrocardiogram lead signals using two electrocardiographs. Therefore, the watch can transmit an electrocardiogram measurement command to the downward lead electrocardiograph 100, 400, 500, 600 after an appropriate time has elapsed since the PPG generated an alarm.

[0128] Upon detecting the alarm, the user touches the corresponding electrode of the watch with the hand opposite the hand wearing the watch. The current sensor in the watch then detects the touch of the opposite hand, prepares for Lead I measurement, and attempts a Bluetooth low energy connection. The user then touches the corresponding electrode of the downward-lead electrocardiograph (watch electrocardiograph 100, ring-type electrocardiograph 400) to their left foot. Current flows from the current sensor in the downward-lead electrocardiograph 100, 400 between the left foot and the hand wearing the downward-lead electrocardiograph 100, 400. When the current sensor in the downward-lead electrocardiograph 100, 400 detects the touch of the left foot and generates an output, the microcontroller in the downward-lead electrocardiograph 100, 400 prepares for ECG measurement and attempts a Bluetooth low energy connection. Meanwhile, in the embodiments of the present invention, the microcontrollers of the patch-type downward lead electrocardiograph 500 and the chest band-type downward lead electrocardiograph 600 can be activated by a method such as a mechanical switch to perform electrocardiogram measurement according to the present invention. Then, the microcontrollers can complete preparations for electrocardiogram measurement appropriate for the present invention and attempt Bluetooth low energy connection.

[0129] When a Bluetooth low energy connection is established between the watch electrocardiograph 200 and the downward lead electrocardiograph 100, 400, 500, 600, the watch electrocardiograph 200 can transmit an electrocardiogram measurement command to the downward lead electrocardiograph 100, 400, 500, 600. Depending on the embodiment, the downward lead electrocardiograph 100, 400, 500, 600 may transmit the electrocardiogram measurement command to the watch electrocardiograph 200.

[0130] If the user desires to perform an electrocardiogram measurement even if the watch's PPG does not generate an alarm, according to the principles of the present invention, i) the user contacts the watch electrocardiograph 200 with a body part corresponding to two electrodes of the downward lead electrocardiograph 100, 400, 500, 600 or operates a mechanical switch, etc., ii) the two electrocardiographs establish a Bluetooth low energy connection, iii) one of the electrocardiographs generates an electrocardiogram measurement command, and iv) the above-mentioned two electrocardiogram lead measurements can be performed.

[0131] The concept and principle of the present invention have been disclosed above, and the contents described in the embodiments of the present invention can be variously implemented based on the concept and principle of the present invention.

[0132] As described above, the present invention has been described using specific details such as specific components and limited embodiment drawings, but this is provided merely to facilitate a more general understanding of the present invention, and the present invention is not limited to the above-described embodiment. Various modifications and variations can be made from such descriptions by those having ordinary knowledge in the field to which the present invention pertains.

[0133] Therefore, the spirit of the present invention should not be limited to the described embodiments, but should include not only the scope of the claims, but also all modifications equivalent to or equivalent to the scope of the claims, which fall within the scope of the spirit of the present invention.

Claims

1. A watch worn by the user on one wrist; a band coupled to said watch; a first electrocardiograph coupled to one of the bands and positioned opposite the bottom surface of the watch; and a second electrocardiograph included in the watch; The first electrocardiograph a first electrode disposed on an inner surface of the band so as to contact the user's wrist, and a second electrode disposed on an outer surface of the band so as to be able to contact the user's left knee or left ankle; The second electrocardiograph a third electrode disposed on a bottom surface of the watch so as to contact the one wrist of the user, and a fourth electrode which can be contacted by the other hand of the user; A wearable device characterized in that the first electrocardiograph and the second electrocardiograph transmit and receive signals wirelessly.

2. The first electrocardiograph measuring a first electrocardiogram lead signal induced between the first electrode and the second electrode, and transmitting the measured first electrocardiogram lead signal to the second electrocardiograph via wireless communication means; The second electrocardiograph measuring a second electrocardiogram lead signal through the third and fourth electrodes; receiving the first electrocardiogram lead signal via wireless communication means; The wearable device of claim 1, wherein the received first electrocardiogram lead signal is compensated for a time delay that occurs during wireless communication so that the first electrocardiogram lead signal and the second electrocardiogram lead signal become two electrocardiogram lead signals sampled at the same time.

3. The wearable device is The wearable device of claim 2, characterized in that four additional electrocardiogram lead signals are calculated using the two electrocardiogram lead signals sampled at the same time to obtain six limb lead signals including lead I, lead II, lead III, lead aVR, lead aVL, and lead aVF.

4. The first electrocardiograph a microcontroller for controlling the first electrocardiograph, the microcontroller comprising: When the first electrocardiograph is not measuring electrocardiogram lead signals, the first electrocardiograph operates in a slip mode, and powers off an amplifier, an AD converter, and a wireless communication means included in the first electrocardiograph; The wearable device of claim 1, characterized in that when changed to activation mode, the amplifier, the AD converter, and the wireless communication means are powered on, the first electrocardiogram lead signal is amplified, AD converted, and wireless communication is performed.

5. The first electrocardiograph includes a current sensor to which power is supplied, the current sensor comprising: When the first electrode contacts the one wrist of the user and the second electrode contacts the left knee or the left ankle of the user, a current flows through the user's body; generating an output signal upon sensing said current; The wearable device of claim 4 , wherein the microcontroller changes from a slip mode to an active mode upon receiving the output signal of the current sensor.

6. 3. The wearable device of claim 2, wherein the time delay value is determined using the following steps (1) to (4): (1) applying one output signal of one signal generator to the first electrocardiograph and the second electrocardiograph in common; (2) the first electrocardiograph and the second electrocardiograph measure the output signals; (3) the first electrocardiograph transmits the measured signal via wireless communication means, and the second electrocardiograph receives the transmitted signal; (4) The waveforms of the signal measured by the second electrocardiograph and the signal received by the second electrocardiograph are compared.

7. The wearable device according to claim 1, wherein the bands are formed so that one band is longer than the other band relative to the watch in order to position the first electrocardiograph.

8. 3. The wearable device according to claim 2, wherein the wireless communication means is a low-power wireless communication system.

9. A method for obtaining multiple electrocardiogram leads using an electrocardiogram built into a watch worn on one wrist and an electrocardiogram attached to a band of the watch, comprising: a step of contacting a first electrode of an electrocardiograph attached to the band with the wrist and a second electrode with the left foot or ankle; a microcontroller built into the electrocardiograph attached to the band is changed to an active mode; When the microcontroller is changed to the active mode, powering on the amplifier, the AD converter and the wireless communication means; amplifying an electrocardiogram lead between the first electrode and the second electrode; converting the amplified analog signal to a digital signal; transmitting the first electrocardiogram lead signal converted into a digital signal to an electrocardiograph built in the watch via the wireless communication means; an electrocardiograph incorporated in the watch receiving the transmitted first electrocardiogram lead signal via wireless communication means; and a step of compensating for a time delay occurring in the wireless communication process of the received first electrocardiogram lead signal so that a second electrocardiogram lead signal measured through electrodes attached to a watch and the first electrocardiogram lead signal become two electrocardiogram lead signals sampled at the same time.

10. 10. The method of claim 9, further comprising: checking whether there is a current flow in a current sensor to determine whether a microcontroller built into an electrocardiograph attached to the band performs electrocardiogram measurement for a predetermined time and then terminates the electrocardiogram measurement.

11. The wearable device of claim 3, wherein the difference in the time points at which the two electrocardiogram lead signals are sampled is smaller than the sampling period in order to obtain the two electrocardiogram lead signals sampled in the same time band.

12. one watch electrocardiograph mounted on one watch body and measuring Lead I; and A wearable device comprising: a single downward lead electrocardiograph that measures one of Lead II or Lead III depending on the placement location; the watch electrocardiograph wirelessly transmits a command to start electrocardiogram measurement, i.e., an electrocardiogram measurement start command, to the one downward lead electrocardiograph; The watch electrocardiograph measures Lead I; The one downward lead electrocardiograph that wirelessly receives the electrocardiogram measurement start command measures one of Lead II or Lead III, and when the one downward lead electrocardiograph wirelessly transmits the measured one of Lead II or Lead III to the watch electrocardiograph, the watch electrocardiograph wirelessly receives the transmitted one of Lead II or Lead III, acquiring two electrocardiogram lead signals measured over the same time band; A wearable device characterized in that four additional electrocardiogram lead signals are calculated using two electrocardiogram lead signals measured in the same time band to obtain six limb lead signals consisting of lead I, lead II, lead III, lead aVR, lead aVL, and lead aVF.

13. One downward lead electrocardiograph measuring one of the leads II and III, a band coupled to the one watch body and disposed at a position facing the bottom surface of the watch body; an electrode disposed on an inner surface of the band so as to contact one of the user's wrists; The wearable device of claim 12, further comprising one electrode disposed on an outer surface of the band so as to be capable of contacting the user's left knee or left ankle.

14. One downward lead electrocardiograph measuring one of the leads II and III, The wearable device according to claim 12, characterized in that it is in the form of a ring worn on one finger.

15. One downward lead electrocardiograph measuring one of the leads II and III, 13. The wearable device of claim 12, comprising electrodes in the form of a patch or chest band that are contacted to the chest.

16. The wearable device of claim 12, wherein the two electrocardiogram lead signals measured in the same time band have identical frequency response characteristics.

17. The wearable device of claim 12 , wherein the two electrocardiogram measurement start command electrocardiogram lead signals measured in the same time band have the same gain characteristics.

18. The wearable device of claim 12, wherein the two electrocardiogram lead signals measured in the same time band have a maximum amplitude error within + / - 5%.

19. The wearable device of claim 12 , wherein the two electrocardiogram lead signals measured in the same time band are sampled at the same sampling rate.

20. The wearable device of claim 12, wherein the wireless communication method between the watch electrocardiograph and the single downward lead electrocardiograph is Bluetooth low energy.

21. The one downward lead electrocardiograph comprises: After the low-power wireless communication connection is established, sampling the electrocardiogram lead signals during one coupling interval; The wearable device according to claim 12 , wherein the sampled data is transmitted during one linked event following the sampling.

22. The connection interval is The wearable device of claim 21, wherein the sampling period of one downward lead electrocardiograph is an integer multiple of the sampling period when sampling one electrocardiogram lead signal.

23. The wearable device of claim 12, wherein the watch electrocardiograph and the single downward lead electrocardiograph sample their respective electrocardiogram lead signals at the same time by sampling their respective electrocardiogram lead signals after the same time has elapsed since the coupling event.

24. The wearable device of claim 12, wherein the operation of calculating the four additional electrocardiogram lead signals and the operation of displaying the six limb lead signals are performed by a smartphone.

25. The electrocardiogram measurement start command, The wearable device of claim 12, wherein the one electrocardiograph generates an alarm after a photoplethysmograph mounted on the one electrocardiograph detects abnormal cardiac activity and generates an alarm.

26. The electrocardiogram measurement start command, 13. The wearable device of claim 12, wherein the downward-lead electrocardiograph or watch electrocardiograph generates an output after a current sensor detects that the user has contacted the user's body with two electrodes of the downward-lead electrocardiograph to measure an electrocardiogram.

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