Device and Method for Measuring Three-Lead ECG in a Wristwatch

[0001] 1. Field of Invention

[0002] This invention relates to a wristwatch with the function of measuring and processing three-lead electrocardiogram (ECG), and more particularly, to a wrist-watch that is capable of measuring three-lead ECG and providing event-related reminders for alerting users to measure ECG in a critical moment determined by a sensing system or a user. In addition, this invention is related to a method for measuring three-lead ECG by the wristwatch.

[0003] 2. Description of Related Art

[0004] Regularly tracking on changes in cardiac function is usually suggested for the elderly to maintain fitness. In hospital, three-lead ECG measurement has been widely used to monitor cardiac function. While accepting a cardiac assessment in hospital, it can often cost time, increase the risk to get affection and not be convenient for the elderly. To be capable of measuring ECG conveniently, portable ECG recording devices have been developed.

[0005] Although portable ECG measuring devices have been introduced to record ECG outside hospital, the need to wear electrodes on the chest and carry cables connecting to the device makes it uneasily to use on an ambulatory and daily base. Some wristwatches have been made for measuring heart rates or heart pulses but have not been equipped with three-lead ECG measurement and arrhythmia analysis which provides more detail information about the cardiac system.

[0006] Standard three-lead ECG indicates a measurement of cardiac potentials leaving from the heart in 3 directions, toward right-arm (RA), toward left-arm (LA), and toward left leg (LL). The lead I of ECG is the cardiac potential difference between LA and RA (LA−RA), the lead II of ECG is the cardiac potential difference between LL and RA (LL−RA) and the lead III of ECG is the cardiac potential difference between LL and LA (LL−LA). Also, 3 augmented leads (lead AVR, AVL and AVF) can be calculated based on the standard three-lead ECG. Lead AVR is RA−(LA+LL)/2=−(I+II)/2, lead AVL is LA−(RA+LL)/2=(I-III)/2, and lead AVF is LL−(RA+LA)/2=(II+III)/2.

[0007] To meet the need of convenience and medical expertise, it is desirable to have a portable device, e.g. a wristwatch, can measure and process three-lead ECG without extra cable connections. Further, if the three-lead ECG data acquired by a portable device can be recorded and transmitted to a personal and hospital computer will be highly convenient and needed.

[0008] The object of this invention is to provide a portable device, a wristwatch, with the function of measuring, recording, and analyzing three-lead ECG. Three electrodes are placed on the front-side/lateral-side, back-side, and strap of the watch separately. When the watch is worn, the electrode in the back-side of the watch contacts the first hand which wears the watch. Then, a finger from the second hand contacts the electrode on the front-side of the watch can form an electrical loop to measure the lead I of ECG (ECG potential difference between right and left arms). To measure the other 2 ECG leads, the wearer needs to bring the electrode on the strap to touch his/her own abdominal area or left leg while the fingers from the second hand still press on the electrode on the front-side of the watch to form a triangle electrical loop. The potential difference between each pair of electrodes represents a lead. The lead I of ECG is the potential difference between the left arm and right arm, the lead II of ECG is the potential difference between the left leg (or abdomen) and right arm and the lead III of ECG is the potential difference between the left arm and left leg (or abdomen). Therefore, standard three-lead ECG can be obtained based on the 3 electrodes. In addition, the trigger to start ECG measurement is an electrode panel that comprises sensing elements on the front-side/lateral-side of the watch. The sensing elements can be detectors of pressure, impedance or infrared to recognize the contact or press of a finger. The watch has the function of providing reminders, which can be in sound, light or vibration or all of them, to notice the user to measure ECG. The events which can induce reminders comprise alarm setups, activity levels, and temperature changes etc.

[0016] Referring to FIG. 1, there is shown a view of a preferred embodiment of the invention including a back 1 and a front 2 view of the wristwatch. In the back-side 1 of the watch, an electrode 3 is inserted for touching the hand which wears the watch. In the front-side 2 of the watch, there is another electrode 4 for fingers from the other hand to press on, while the watch is worn on one hand. An electrode panel 12 comprising the electrode 4 on the front-side 2 of the watch and sensing elements 6 is placed on the front-side of the watch. The sensing elements 6 can detect pressure, impedance or infrared for recognizing the contact or press made by fingers to initiate ECG measurement. A display 7, such as a liquid crystal display (LCD), is on the front-side of the watch. The display 7 can demonstrate in text 15, which includes time, heart rate, condition (normal or arrhythmia), and graph/animation, which is for event reminding 13 and ECG waveforms 14. To modify watch function and displaying contents, at least 1 control button 9 is set on the watch. To exhibit event-related reminders, output devices for light 8 (for example, light emitting diode (LED), LCD, organic light emitting diode (OLED)) and/or sound 10 (for example, a miniature buzzer or speaker) may be positioned in the watch with an opening on the watch surface. The watch can also have a miniature motor inside to provide the function of vibration as a reminder.

[0017] Referring to FIG. 2, an electrode 5 is placed on the outer side of the strap 11 of the watch for making connection with the left leg or abdomen to form electrical loops for three-lead ECG measurement.

[0018] Referring to FIGS. 3A to 3D, one of the methods according to the invention for measuring three-lead ECG is illustrated. The watch 25 is worn tightly on one hand 22 (FIG. 3A). In FIG. 3B, one finger 23 from the other hand 21 presses on the sensing elements 6 and another finger 24 from the other hand 21 presses on the electrode 4 on the front 2 of the watch simultaneously. At the same time, the electrode 5 (as shown in FIG. 2) on the strap 11 of the watch 25 contacts the skin in the wearer's abdominal area to form a triangle electrical loop. In addition, the placement of fingers can be altered to be one finger (any one finger 27 from the other hand in FIG. 3C, or the thumb 28 from the other hand in FIG. 3D) touching both the sensing elements 6 and electrode 4 on the electrode panel 12 to trigger and make measurement. After measuring ECG, the data obtained can be stored in a flash memory plugged or inserted in the watch and/or transmitted via a wireless module 26, 56 to a personal computer or hospital computer 62.

[0019] Referring to FIGS. 4A to 4D, another method according to the invention for measuring three-lead ECG is illustrated. The watch is worn tightly on one hand 22 (FIG. 4A). In FIG. 4B, one finger 23 from the other hand 21 presses on the sensing elements 6 and another finger 24 from the other hand 21 presses on the electrode 4 on the front 2 of the watch simultaneously. At the same time, the electrode 5 (as shown in FIG. 1) on the wrist-band 11 of the watch contacts the skin on the wearer's left thigh area 31 to form a triangle electrical loop. In addition, the placement of fingers can be altered to be one finger (any one finger 27 from the other hand in FIG. 4C, or the thumb 28 from the other hand in FIG. 4D) touching both the sensing elements 6 and electrode 4 on the electrode panel 12 to trigger and make measurement. After measuring ECG, the data obtained can be stored in a flash memory plugged or inserted in the watch and/or transmitted via a wireless module 26, 56 to a personal computer or hospital computer 62.

[0020] Referring to FIGS. 5A to 5C, 3 examples of sensing elements are demonstrated. Firstly, FIG. 5A shows a switch sensor 77 on a circuit board 76 embedded in the watch. When one finger 71 presses 73 on a soft surface 72 of the sensing elements 6, a solid pellet 78 inserted in a floating broad 74 under the soft surface 72 is pushed down to turn on the switch 77 to start ECG measurement. The floating broad is supported by springs 75 which stand on the circuit board 76. Secondly, FIG. 5B shows a light source 82 and a photo detector 83 on the circuit board 76 embedded in the watch. When a finger 71 is placed on a small hole which is on the surface 81 of the sensing elements 6, the light (e.g. infrared) released by the light source 82 reaches 84 the finger and reflects 85 back to the photo detector 83. After receiving light, the photo detector 83 generates a potential to initiate ECG measurement. Thirdly, FIG. 5C shows an impedance detecting circuit is set on the circuit board 76 embedded in the watch. When one finger 71 touches a conductive surface 91 on the sensing elements 6, a low-energy current 93 released by a wire 92 goes through fingertip 71 and back to the circuit board via another wire 94. The voltage difference between the output and input currents to the circuit board 76 is used to be a trigger to start ECG measurement.

[0021] Referring to FIG. 6, the method to obtain three-lead ECG is shown. The method to compute standard three-lead ECG is described as follows: the lead I of ECG is the cardiac potential difference between LA and RA (LA−RA), the lead II of ECG is the cardiac potential difference between LL and RA (LL−RA) and the lead III of ECG is the cardiac potential difference between LL and LA (LL−LA). In this invention, the potential difference between each pair of electrodes is obtained by differential amplifiers 41,42,43. The identification of ECG leads depends on which hand is wearing the watch. When the watch is worn on the left hand, the potential difference between electrodes 3,4 on the front-side and back-side of the watch is identified as lead I 44, the potential difference between electrodes 4,5 on the front-side and the band of the watch is identified as lead II 45, and the potential difference between electrodes 3,5 on the back-side and band of the watch is identified as lead III 46.

[0022] When the watch is worn on the right hand, the potential difference between electrodes 3,4 on the front-side and back-side of the watch is identified as—lead I 44, the potential difference between electrodes 4,5 on the front-side and the band of the watch is identified as lead III 45, and the potential difference between electrodes 3,5 on the back-side and band of the watch is identified as lead II 46. The reference potential of the ECG circuits is set as the combination of the signals from the 3 electrodes. All ECG data go through filters 47, 48, 49 to sharpen signals and then an analog-to-digital converter 50 to change analog signals to be digital data for a microprocessor 54 disposed in the watch. For augmented three-lead ECG, the calculation method is according to the standard three-lead ECG as follows: Lead AVR is RA−(LA+LL)/2=−(I+II)/2, lead AVL is LA−(RA+LL)/2=(I−III)/2, and lead AVF is LL−(RA+LA)/2=(II+III)/2. All circuits for ECG measuring are embedded and hidden inside the watch or the strap 11.

[0023] Referring to FIG. 7, a general block diagram of the embodiment of the invention and the flow of signal collecting, processing and transferring is illustrated. The invention has a microprocessor 54 in the center. The inputs for inducing spontaneous reminders for users to measure ECG include activity levels and temperature changes. Activity levels are measured by an accelerometer 51 and temperature changes are measured by a thermometer 51. The signals collected by the accelerometer and thermometer 51 pass an A/D converter 50 before entering the microprocessor 54. When the activity level of users is intensive for a critical period of time or when the temperature changes dramatically, the microprocessor 54 will order the reminding function to be active in a form of light, sound or vibration 58 or all of them. Also, users 59 of the invention can use the control button 60 or wireless settings to set time alarm for reminding him/her-self to measure ECG. After receiving the reminding signals, users 59 may start ECG measurement by pressing on the electrode panel 53 and positioning the watch as in FIG. 2 and FIG. 3 or turn off reminders by operating the control buttons 60. After measuring, ECG circuits 52 sent acquired data through the A/D converter 50 to the microprocessor 54 to process and transfer data to the flash memory 55, wireless module 56, and/or display 57. The display 57 can show users 59 times, heart rate, waveforms and any other information 61, such as activity level and temperature, if needed. The data recorded in the flash memory 55 or transmitted by the wireless module 56 can eventually reach personal or hospital computers 62 for cardiac experts to make specific analyses.

[0024] A unique design and concept of a wristwatch which can measure three-lead ECG is shown and described here. Many changes and modifications can be carried out without departing the scope of the specific embodiment described herein. The description herein is intended to be illustrated only and is not intended to be limitative. The invention is intended to be limited only by the scope of the appended claims.