The present disclosure relates to portable electrocardiography measurement devices that may be able to perform electrocardiographic recordings for an extended amount of time, and methods for use thereof.

Background of invention

Electrocardiography is the process of producing an electrocardiogram. It is a graph of voltage versus time of the electrical activity of the heart using electrodes placed on the skin. These electrodes detect the small electrical changes that are a consequence of cardiac muscle depolarization followed by repolarization during each cardiac cycle. Changes in the normal ECG pattern occur in numerous cardiac abnormalities, including cardiac rhythm disturbances, inadequate coronary artery blood flow, and electrolyte disturbances.

A standard handheld electrocardiography device typically records the heart's electrical activity for only a few seconds. This can detect abnormalities that are constant; however, sometimes abnormal heart rhythms and inadequate blood flow to the heart muscle occur only briefly or unpredictably. These types of problems require prolonged measurements of the heart’s electrical activity. One type of device that may be used for this purpose is continuous ambulatory electrocardiography, in which the ECG is recorded continuously for typically 24 to 48 hours while the person engages in normal daily activities. Another approach for capturing rare events is the use of event-based electrocardiography, in which the ECG is continuously monitored for an extended amount of time, for example up to a week, but the data is only stored when the device receives a trigger from the subject that an abnormal event has occurred.

While these types of devices have provided means for acquiring rare events, they are typically bulky and offer limited resolution, and thereby the measurement data may not provide sufficient details of the heart’s electrical activity in order to gain clinical insights into a subject’s suspected condition. There is consequently a significant need for a small and portable device that is able to acquire electrocardiography data for a prolonged time, with sufficient detail in order to correctly diagnose a subject’s suspected condition. Summary of invention

The present inventor has realized that electrocardiography devices can be made significantly more portable, and easier to use, while still being capable of providing high resolution measurement data.

The present invention therefore in a first aspect relates to a portable electrocardiography device comprising:

• an arrangement of electrodes located on a first plane defined by a first side of the portable electrocardiography device, including: o three primary electrocardiography electrodes or device connectors arranged in a triangular pattern; o a primary common mode rejection electrode or connector; and

• a housing comprising: o a power source, such as a battery; and o a processing unit in electrical communication with the electrodes or connectors, said processing unit configured for receiving an electrocardiography signal from each electrode and processing the electrocardiography signals into electrocardiography data.

The three primary ECG electrodes may be provided at fixed locations of the housing, preferably at each corner of a triangular housing. With the primary ECG electrodes provided at fixed locations with respect to the housing, the distances and angles between the primary ECG electrodes may have already been set as part of the construction of the electrocardiography device. The distances and angles between the primary ECG electrodes may thereby not be affected by how the primary ECG electrodes are attached to the subject. This is in stark contrast to conventional electrocardiography devices that typically rely on the use of electrical cables from a remote located device to the ECG electrodes.

The ECG electrodes may thereby be provided in a suitable pattern for obtaining high resolution ECG signals. For example, the electrocardiography device may be provided with three ECG electrodes that form an equilateral triangular pattern. Said pattern may comprise sides that are less than 15 cm in length. The device may thereby be small and portable, offering the subject an ability of recording ECG signals for an extended period of time. The ECG device preferably comprises a Wilson reference generator circuit that is used in a driven right leg configuration. The output of the Wilson reference generator circuit is expected to be the common mode interference. By inversion of this signal and provided to the common mode rejection electrode, the common mode interference is actively suppressed.

The ECG electrodes preferably comprises a first plane defined by a first side of the housing, and wherein the ECG electrodes are located at each corner of said first side of the housing. The electrocardiography device may further be configured to have ECG electrodes that are to be located at positions of a chest that have a low degree of muscles, fat tissue and breast tissue.

Preferably, the portable electrocardiography device further comprises a detachable electrocardiography pad comprising three secondary electrocardiography electrodes arranged in a triangular pattern on a first side of the detachable electrocardiography pad facing a user. Such a detachable electrocardiography pad may have a first side that can be arranged, for example by means of a patch to the user, and a second side facing the housing. The detachable electrocardiography pad may thus further comprise pad connectors arranged on the second side of the detachable electrocardiography pad facing the housing of the portable electrocardiography device and matching an arrangement of three corresponding device connectors of the portable electrocardiography device. Since the three device connectors and the three secondary electrocardiography electrodes not necessarily have the same layout, the three secondary electrocardiography electrodes may be connected to the pad connectors by conductors on or in the detachable electrocardiography pad. For improved placement on the user, the detachable electrocardiography pad preferably further comprises an extension area extending from the corner corresponding to the VLL electrode, the extension area extending outwardly in a direction from the center of the generally triangular shape, wherein the VLL electrode is arranged in the extension area.

The electrocardiography device may for example be configured to comprise two ECG electrodes adapted to be attached symmetrically across the sternum of a subject, and may comprise a third ECG electrode that is adapted to be attached to an inferior centrally located position of the sternum. Such a configuration and positioning of said device, may lead to an avoidance of the parts of the chest of the subject where there is an abundance of muscle tissue, fat tissue and/or breast tissue. Signals obtained from the two symmetrically superior located electrodes may be used to suppress noise from electrical pulses to the muscles but additionally also artefacts due to movements of the subject.

The location of the ECG electrodes allows for a larger variation between the shape of subjects and their hearts, while maintaining high signal-to-noise measurements, as compared to conventional electrocardiography devices. The portable electrocardiography device may thereby result in more accurate P-wave, QRS-complex and ST segments than these conventional electrocardiography devices.

The electrocardiography device preferably comprises means for wireless communication, for example with a cloud-based server and/or a personal computing device, such as a smartphone or a tablet. The electrocardiography device may be configured such that the following attachment to the chest area of the subject, said subject may communicate with the electrocardiography device through the personal computing device. The subject may for example request that ECG data is provided from the electrocardiography device to the personal computing device, for displaying on said personal computing device and thereby ensuring correct electrode placement and operation.

The electrocardiography device may further be configured to receive a first subject input from the subject, for registration of an occurrence of an abnormal event. For example chest pain or heart palpitation. The electrocardiography device is preferably configured such that it, upon receiving said first subject input, stores a recording related to said registration. The stored data may for example be in the form of a time point, or the stored data may be in the form of ECG data provided from ECG signals retrieved in a time interval defined by a predetermined time period before receiving the first subject input and a predefined time interval after receiving said first subject input.

The electrocardiography device may further be equipped with means for communication with a remote server, such as over an LTE Cat M1 network. By communication with a remote server, the electrocardiography device may be able to transmit registered and/or processed data, such as ECG data, to said remote server. The ECG data uploaded to the cloud server may be further processed, for example into multiple additional leads, and investigated by physicians through a web application. In a second aspect, the present invention relates to a method for performing electrocardiographic measurements of a subject, comprising:

• providing a portable electrocardiography device according to any one of the preceding claims ;

• positioning the electrocardiography device on the chest of the subject; and

• obtaining electrocardiography signals from said electrodes; thereby performing electrocardiographic measurements of the subject.

It is a preference that the electrocardiography device is configured such that the ECG electrode may be placed on the subject in an equilateral triangular pattern, wherein each side of said triangular pattern is no more than 15 centimeters.

It is a further preference that the electrocardiography device is positioned on said subject symmetrically on the subject, such as in order to avoid areas with fat tissue, muscle tissue and/or breast tissue.

Description of drawings

Fig. 1 shows an infrastructure for accurate ECG measurement by a portable electrocardiography device, according to an embodiment of the present disclosure. Fig. 2 shows a number of subject interfaces of a smartphone app for presenting ECG data, obtaining status of the ECG device, and registering of events, according to an embodiment of the present disclosure.

Fig. 3 shows a number of subject interfaces of a web application for use by a medical professional comprising ECG data obtained during an extended amount of time, according to an embodiment of the present disclosure.

Fig. 4 shows a schematic illustration of an electrocardiography device, comprising an ECG pad and a housing, according to an embodiment of the present disclosure.

Fig. 5 shows a block diagram describing a process for continuously obtaining a common mode interference signal, according to an embodiment of the present disclosure.

Fig. 6 shows a schematic illustration of a detachable electrocardiography pad and a housing for an electrocardiography device, according to an embodiment of the present disclosure. Detailed description of the invention

The present invention relates, in a first aspect, to an electrocardiography device that can be used for an extended period of time, and thereby register and/or detect the electrical activity of the heart for an extended period of time. Said electrocardiography (ECG) device is preferably configured such that it can be worn with ease. For example, the electrocardiography device may not be heavier than that it can be attached to the chest with suitable means, such as by adhesive, without discomfort to the subject. The ECG may further be shaped in a way that it can easily be worn under garments, such as clothing, i.e. said electrocardiography device is not bulky. It is a further preference that the electrocardiography device consists of a single unit, without electrical wiring to secondary battery units and/or recording units. Instead it is a preference that the electrocardiography device is configured as a compact and light-weight portable device, that a subject may wear and/or carry around with ease for an extended amount of time.

In an embodiment of the present disclosure, the electrocardiography device comprises a housing. It is a preference that the housing is substantially planar, having a first side, for facing the subject when in use, and a second side for facing away from the subject when in use. The housing of the electrocardiography device may comprise visual indicators of the present status of the electrocardiography device. For example if the battery needs to be replaced within a certain amount of time and/or if any of the memories of the electrocardiography device, for storing data, is about to be full. The housing of the electrocardiography device may further be substantially waterproof, such as waterproof. This may be achieved by the use of a housing that is adapted such that only electrical contacts are exposed to the surrounding environment of the housing. For example, the housing may comprise a number of apertures, at which said electrical contacts may be positioned. The electrical contacts and/or the housing may be sealed, such that the electrocardiography device is capable of withstanding water for an extended amount of time. As previously mentioned, the electrocardiography device may be configured such that it allows for a subject to wear and use the electrocardiography device without interfering with the normal daily routines of the subject. Thereby, by making the electrocardiography device small, lightweight, and waterproof the subject may be able to carry out the normal daily routines, such as showering, without having to take any special considerations to the electrocardiography device. In a further embodiment of the present disclosure, the electrocardiography device comprises a battery. Preferably said battery is rechargeable, by for example wired and/or wireless charging. The battery may for example be adapted for wireless charging by inductive coupling, resonant inductive coupling and/or capacitive coupling.

In a further embodiment of the present disclosure, the electrocardiography device comprises a first memory, such as for storing ECG data and/or ECG signals. It is a preference that the capacity of the first memory is selected such that the electrocardiography device is capable of storing continuous ECG data obtained during at least 7 days, more preferably at least 15 days, yet more preferably at least 30 days.

In a preferred embodiment of the present disclosure, the electrocardiography device comprises an arrangement of electrodes located on a first plane defined by a first side of the housing. Thus, the first side may as such be a first side of the housing. Said arrangement of electrodes may consist or comprise of a number of electrodes such as three or four. In a preferred embodiment of the present disclosure, the arrangement of electrodes consists of three ECG electrodes and a Common mode rejection electrode. It is a further preference that the ECG electrodes are located on the first side of the housing of the electrocardiography device. It is a further preference that the three ECG electrodes are located in a triangular pattern. In yet a preferred embodiment of the present disclosure, the electrocardiography device comprises a Common mode rejection electrode that is located in the same plane as the ECG electrodes, for example within the pattern (e.g. triangular) formed by the three ECG electrodes. In a further preferred embodiment of the present disclosure the Common mode rejection electrode is located substantially in the center of the triangular pattern formed by the ECG electrodes. While the ECG electrodes may form a triangular pattern, it should be noted that the housing may not necessarily be provided in a similar shape. Instead it may be a preference that the housing is provided in a shape that minimizes the area of the first side, and/or minimizes the projected area of the electrocardiography device onto a surface parallel with the first surface. Thereby, the device may be provided in for example a substantially three bladed shape, such as three bladed boomerang and/or a three bladed propeller. The housing of the electrocardiography device may thereby have three arms extending outwards from the centrally located Common mode rejection electrode. Each arm of said three arms may have any length independent of the other arms, and may further extend outward from the central part of the housing at any angle. The special case being wherein each arm forms a 60 degree angle to the adjacent arm, and wherein the length of each arm is identical. In this configuration the pattern of the electrodes may form an equilateral triangle.

In a further embodiment of the present disclosure, the electrocardiography device comprises a processing unit. Said processing unit may be in electrical communication, such as direct electrical communication, with the electrodes, such as each electrode. It is a preference that the processing unit is configured such that it is able to receive ECG signals from each electrode. It is a further preference that the processing unit is configured for processing of the ECG signals, such as into ECG data.

Communication means

In a further embodiment of the present disclosure, the electrocardiography device comprises means for wireless communication, such as means for communication over a mobile network, such as 4G LTE and/or 5G. Furthermore, said means for wireless communication may comprise means for communication by Bluetooth, such as Bluetooth Low Energy. Bluetooth Low Energy (BLE) uses the same 2.4 GHz radio frequencies as classic Bluetooth, which allows dual-mode devices to share a single radio antenna, but uses a simpler modulation system. It is a preference that the electrocardiography device comprises at least one means for long-range communication, such as LTE, and one means for short-range communication, such as BLE. Thereby, the electrocardiography device may be able to communicate with electronic devices that are in proximity of the electrocardiography device and/or subject, and furthermore communicate with remote devices, such as remote servers. The electrocardiography device may for example be able to communicate with a personal computing device, such as a smartphone, that is in proximity of the electrocardiography device, for example by BLE. Furthermore, the electrocardiography device may be able to communicate with a remote server, such as a cloud server, over LTE. Personal computing device may be any device that may be operated by an endsubject, and may include smartphones, tablets, stationary computers, such as a desktop computer, portable computers, such as a laptop. In a preferred embodiment of the present disclosure, the personal computing device is provided with software for displaying an interface to the subject for allowing communication with the electrocardiography device, such as retrieval of the electrocardiography device status, present ECG data, as well as past ECG data recordings. In a further embodiment of the present disclosure, the electrocardiography device is configured such that it may communicate with remote devices through devices in its proximity. Thereby, for example, the electrocardiography device may communicate by Bluetooth with a smartphone that, in turn, communicates over mobile networks with a remote server.

First subject input

In a further embodiment of the present disclosure, the electrocardiography device is configured for receiving a first subject input. Said first subject input may be provided to the electrocardiography device by direct interaction with the electrocardiography device, such as by the push of a button extending out from an aperture in the housing of the electrocardiography device , by voice command, and/or touch sensitive buttons/or screens on a surface of the housing. Furthermore, a subject may interact indirectly with the electrocardiography device, such as by use of the personal computation device. The subject may thereby interact with the personal computation device which, in turn, sends commands to the electrocardiography device. The first subject input may thereby be provided by the subject through the interaction with the personal computation device and transmitted to the electrocardiography device by the personal computation device.

In a further embodiment of the present disclosure, the electrocardiography device is configured to, upon receiving the first subject input, store ECG data and/or ECG signals. The subject may, prior to use, have been instructed to, upon notice of an abnormality, such as palpitation and/or chest pain, provide the electrocardiography device with the first subject input, such as by interacting with the personal computation device. The electrocardiography device may be configured to, upon receiving the first subject input, store ECG data and/or ECG signals obtained during a recording interval, said recording interval may be defined by a predetermined time before receiving said first subject input and a predetermined time after receiving said first subject input. The recording interval may be symmetric around the time point of providing the first subject input, such as 5 minutes before said provision and 5 minutes after said provision. The recording interval may further be asymmetrically disposed in time around the time point of providing the first subject input, such as 7 minutes before said provision and 2 minutes after said provision. In a further embodiment of the present disclosure, the electrocardiography device is configured to, upon receiving the first subject input, store ECG data and/or ECG signals to a second memory. It should be noted that the first memory and the second memory may be different partitions of the same memory unit, or may be two separate physical memory units. It is a preference that the electrocardiography device comprises both the first and the second memory. During use, the electrocardiography device may be configured to store ECG signals and/or ECG data on the first memory in a loop recording manner. ECG recordings may thereby be carried out continuously and ECG signals and/or ECG data may be continuously stored on the first memory. For loop storage of the ECG data and/or ECG signals, the data quality, such as the sampling rate, and the memory size determines how old recordings are present on the first memory before being written over. In one embodiment of the present disclosure, the first memory has a capacity to store at least data obtained during a time interval equal to the recording interval. In an alternative embodiment of the present disclosure, the present disclosure is capable of recording during a substantial amount of time, such as at least 7 days. If the intended observation period, during which the subject is to wear the electrocardiography device, is less than the storage capability of the first memory there may not be a need for a second memory. Therefore, in a further embodiment of the present disclosure, the electrocardiography device is configured to, upon receiving the first subject input, to register/add a time point to the ECG data. The time point may thereafter be stored, together with the remainder of the ECG data. The time point may thereafter serve the purpose of indicating when the subject noticed the occurrence of an abnormal event, such as palpitations or chest pain.

In a further embodiment of the present disclosure, the device is configured to, upon receiving a second subject input, continuously transmit ECG data to the personal computing device, such as low-resolution ECG data for ensuring correct placement of the electrodes.

In a further embodiment of the present disclosure, the said device is configured to periodically, such as upon recharging of the battery, transmit stored ECG data, such as from the secondary memory, to the cloud-based server. Electrical components

In a further embodiment of the present disclosure, the electrocardiography device is configured for continuously receiving ECG signals from the ECG electrodes. In yet a further embodiment of the present disclosure the electrocardiography device is configured for continuous processing ECG signals into ECG data. The electrocardiography device may for example comprise a processing unit that is configured for continuously receiving ECG signals from the ECG electrodes. Furthermore the processing unit may be configured for continuous processing of ECG signals into ECG data.

ECG signals may be the signals received from the electrodes, such as the ECG electrodes and/or the Common mode rejection electrode. Preferably the processing unit is configured to receive and/or process the ECG signals from the ECG electrodes and the Common mode rejection electrode. The processing unit may process the ECG signals into ECG data and preferably comprises at least analog-to-digital conversion. Furthermore, data may be removed and/or added in the processing, for example time points may be added to the ECG data by for example an on-board real time clock.

In a further embodiment of the present disclosure, the electrocardiography device is configured to automatically and continuously receive and/or process ECG signals upon connecting each ECG electrode to an electrode pad. The electrocardiography device may thereby require a minimal amount of interaction from a subject, instead the only requirement is that the electrocardiography device is connected to the electrode pads. Preferably at least the ECG electrodes, such as at least the ECG electrode and the Common mode rejection electrode. Thereby, if the electrocardiography device detects that there is no electrical connection to an electrode pad, the recording may not start. It is a preference that the electrode pad is provided in a material that allows for good adhesion to the skin of the subject in addition to allowing normal skin respiration. The electrode pad may for example be provided in a soft cloth material that allows the skin to breathe and stretch with the movement of the subject. Alternatively the electrode pads may be provided in a non-porous backing material. In a preferred embodiment of the present disclosure the electrodes and/or the electrode pad is provided in Ag/AgCl. In a preferred embodiment the electrode pads are Ag/AgCl electrodes. In a further embodiment of the present disclosure, the electrocardiography device is configured for loop recording of ECG data, such as on a first memory. The electrocardiography device may thereby, depending on the quality of the ECG data, such as the sampling rate, and the capacity of the first memory, store data during a specific time period before the latest processed data replaces the first processed data. Loop recording may thereby allow for continuous recording even if the first memory reaches full capacity.

In a further embodiment of the present disclosure, the electrocardiography device is configured to receive the first subject input from the personal computation device, input means located on said electrocardiography device, such as a button or touch screen, and/or by voice command from a subject. The electrocardiography device may thereby comprise a microphone to register voice commands.

It is a preference that the battery has a capacity that allows the electrocardiography device to continuously record and/or measure ECG signals without being recharged and/or replaced. It is a preference that the electrocardiography device is capable of being used while in charging mode. Thereby, the electrocardiography device may continuously retrieve data, even if the electrocardiography device comprises a rechargeable battery that is being recharged. Recharging of the electrocardiography device may be performed by wired and/or wireless charging.

CMR

A driven right leg circuit or DRL circuit is an electric circuit that is often added to biological signal amplifiers to reduce common-mode interference. Biological signal amplifiers such as ECG (electrocardiogram) EEG (electroencephalogram) or EMG circuits measure very small electrical signals emitted by the body, often as small as several micro-volts (millionths of a volt). Unfortunately, the subject's body can also act as an antenna which picks up electromagnetic interference, especially 50/60 Hz noise from electrical power lines. This interference can obscure the biological signals, making them very hard to measure. Right leg driver circuitry is used to eliminate interference noise by actively cancelling the interference.

The right leg drive (RLD) is a programmable operational amplifier that is intended to control the common-mode level of the subject of the ECG device and thereby improving the AC CMRR of the entire system. In a typical application, the common- mode level of the subject’s body is measured by a Common-Mode Detector. When used in an inverting amplifier topology, the common mode rejection electrode is driven by the RLD to counter any differences between the reference voltage and the detected common-mode level. This reduces the amount of power-line common-mode interference.

In an embodiment of the present disclosure, the ECG device features a Wilson reference block, such as consisting of three buffer amplifiers and resistors, that can generate the voltages for the Wilson Central Terminal and/or Goldberger terminals.

In a further embodiment of the present disclosure the Common-mode detector circuit is a Wilson reference generator circuit.

For the Wilson Central Terminal, there are three main ECG leads that are measured differentially, Lead I (LA-RA), Lead II (LL-RA), Lead III (LL-LA). The Wilson Central Terminal is defined as the average of the three limb electrodes, RA, LA and LL, thereby the Wilson Central Terminal is (RA+LA+LL)/3. This is typically a preferred output of the Wilson Reference Generator Circuit, which is the sum of (BUFi + BUF2 + BUFsj/S. Each of the buffer amplifiers, BUF1, BUF ₂ , and BUF ₃ may be connected to one of the ECR electrodes, thereby BUF1 may be connected to RA, BUF ₂ , may be connected to LA, and BUF3, connected to LL. A non-zero Wilson Central Terminal is expected to have been caused by common-mode interference. Thereby, an inverted commonmode interference signal applied to the subject may advantageously be used to suppress the common-mode interference.

The right leg drive (RLD) may be a programmable operational amplifier that is intended to control the common-mode level of the subject of the ECG device and thereby improving the AC CMRR of the entire system. In a typical application, the commonmode level of the subject’s body is measured by a Common-Mode Detector. When used in an inverting amplifier topology, the common mode rejection electrode may be driven by the RLD to counter any differences between the reference voltage and the detected common-mode level. This reduces the amount of power-line common-mode interference.

The negative input terminal of the RLD op-amp may always be connected to the RLDINV pin. By default, the positive input terminal of the RLD op-amp may be routed to the RLDIN pin. However, the positive input terminal may be routed internally to the RLD reference. This will allow connecting the output of the analogue pace instrumentation amplifier to the RLDIN pin. The output of the RLD operational amplifier may always be connected to the RLDOUT pin, and in addition, can be connected to one of the IN1-IN6 terminals.

In an embodiment of the present disclosure, the common mode rejection electrode may be driven by the RLD to counter any differences between the reference voltage and the detected common-mode level. This may thereby act to reduce the amount of powerline common-mode interference. Typically, the ECG device comprises three measurement electrodes providing three in signals, such as IN1 , IN2, and IN3, each being the ECG signal of each electrode. The in-channels (IN1 , IN2, and IN3) are used in a driven right leg circuit in order to eliminate measurement noise by actively cancelling the common-mode interference. These in signals are thereby used to derive an inverted signal of the common-mode interference. The in signals may be provided to a Wilson reference generator circuit. First, said inputs may be routed to a Wilson reference electrode amplifier that filters out the background noise. This noise may for example be the sum of Lead I, Lead III, -Lead II. Given the conventional notation, a non-zero sum of the above equation represents noise. By routing the output of the Wilson reference electrode amplifier (Wilson ref.) through the Wilson reference output (WCT) and the Right-leg drive amplifier negative to the RLD amplifier. The measured noise may be used to produce an inverted signal of the noise, that is output to the Right-leg drive amplifier output (RLDOUT). This signal, the inverted noise signal, may thereafter be fed to the common mode rejection electrode for active cancelling of the common-mode interference.

For the Wilson Central Terminal, there are three main ECG leads that are measured differentially, Lead I (LA-RA), Lead II (LL-RA), Lead III (LL-LA). The Wilson Central Terminal is typically defined as the average of the three limb electrodes, RA, LA and LL, thereby the Wilson Central Terminal may be defined as (RA+LA+LL)/3. This may be the output of the Wilson Reference Generator Circuit, which is the sum of (BUFi + BUF ₂ + BUF ₃ )/3. Each of the BUFi, BUF ₂ , and BUF ₃ are connected to one of the ECR electrodes, thereby BUFi may be connected to RA, BUF ₂ , may be connected to LA, and BUF ₃ , connected to LL. In an embodiment of the present disclosure, the Wilson Central Terminal is inverted and applied to the common mode rejection electrode. In an embodiment of the present disclosure, the right-arm (RA), left-arm (LA), left-leg (LL) and right-leg (RL) electrodes are connected to the IN1 , IN2, IN3 and IN4 pins respectively, as shown in Fig. 5. The ECG device may be configured to use the Common-Mode Detector to measure the common-mode of the system by averaging the voltage of input pins IN1 , IN2 and IN3, and may subsequently use this signal, the common mode interference signal, in the right-leg drive feedback circuit. The output of the RLD amplifier, the inverse of the common mode interference signal, is preferably connected to the common-mode rejection electrode through IN4 to drive the commonmode of the system.

In an embodiment of the present disclosure, the device is configured to measure the Wilson’s central terminal. Said measurement may be the result of a signal processing, such as the output provided by the Wilson Reference Generator Circuit, such as when said circuit is provided with the signal of the three ECG electrodes. Preferably the device is configured for continuously measuring the Wilson’s central terminal.

In a preferred embodiment of the present disclosure, the device is configured to invert the Wilson’s central terminal, such as the measurements of the Wilson’s central terminal, and provide it, such as apply it, to the common mode rejection electrode. The device may for example comprise a Wilson Central Terminal based active right leg drive circuit. The common mode rejection electrode may thereby provide a signal to the subject that is the inverse of the common mode interference, and consequently actively suppress noise.

In an embodiment of the present disclosure the common mode interference signal is a measured Wilson central terminal, such as by a Wilson reference generator circuit. In another embodiment of the present disclosure, the common mode interference signal is a measured common mode, such as by a common mode detector circuit.

For example the right-arm (RA), left-arm (LA), left-leg (LL) and right-leg (RL) electrodes may be connected to an input pin each of the ECG device, such as the IN1 , IN2, IN3 and IN4 pins respectively. The ECG device may thereafter use the Common-Mode Detector to measure the common-mode of the system by averaging the voltage of input pins IN1 , IN2 and IN3, and uses this signal in the right-leg drive feedback circuit. The output of the RLD amplifier is connected to RL through IN4 to drive the common-mode of the system. Three electrodes may be placed toward the Right Arm (RA), Left Arm (LA), and Left Leg (LL) and sense the electric potentials from the heart. The ECG leads are derived as the differential signals between two electrodes: Lead I = LA - RA, Lead II = LL - RA, Lead III = LL - LA.

Augmented leads provide enhanced vector information to determine the heart’s electrical axis (aVR, aVL, aVF). These are derived via the midpoint of two limbs with respect to the third limb: aVR = RA - (LA + LL) / 2, aVL = LA - (LL+RA) / 2, aVF = LL - (LA + RA) / 2.

In a preferred embodiment of the present disclosure, the device is configured to derive ECG signals from the ECG electrodes to an inverted common-mode interference signal. The common-mode interference signal may thereafter be stored and/or applied to the common mode rejection electrode. Thereby, the common-mode interference signal may be provided back to the subject, in order to actively cancel common-mode interference.

In an embodiment of the present disclosure, the ECG signals from the ECG electrodes are connected to the Wilson reference generator circuit, and wherein the Wilson reference generator circuit is configured to generate a common-mode interference signal. Preferably, said common-mode interference signal is the inverse of the common-mode interference and may be derived/obtained by measuring the deviation of the Wilson Central Terminal from the center of the ECG electrodes.

In yet an embodiment of the present disclosure, the inverter stage is configured to invert the common-mode interference signal to the inverted common-mode interference signal. The inverter stage may comprise or consist of an RLD amplifier. Thereby, the inversion of the common mode interference signal may be performed by connecting the common-mode interference signal to the RLD amplifier. Preferably, the output from the inverter stage, such as the RLD amplifier is connected to the common mode rejection electrode, and thereby said output may be applied to the subject, such as to the centrally located common mode rejection electrode. In yet another embodiment of the present disclosure, the inverted common-mode interference signal is connected to the common mode rejection electrode to actively cancel common-mode interference.

Data processing

In a further embodiment of the present disclosure, the ECG data comprises or consists of two stored ECG leads, such as Lead I and Lead III. The processing unit of the electrocardiography device may use the ECG signals to produce a number of leads. It is a preference that the ECG data consists of two ECG leads, such as Lead I and Lead III. These leads may be used by the electrocardiography device, and or another processing unit, such as a remote server, to produce additional leads. For example the two leads may be used to produce three standard leads and further a number of augmented leads, for example three augmented leads. It is a preference that the two stored leads are two bipolar leads and that these may be used to produce a third bipolar lead. Furthermore, the two stored bipolar leads may be used to produce a number of augmented leads.

Leads I, II and III are typically called the limb leads. The electrodes that form these signals are normally located on the limbs, one on each arm and one on the left leg. The limb leads form the points of what is known as Einthoven's triangle.

Leads aVR, aVL, and aVF are commonly referred to as the augmented limb leads. They are derived from the same three electrodes as leads I, II, and III, but they use Goldberger's central terminal as their negative pole. Goldberger's central terminal is a combination of inputs from two limb electrodes, with a different combination for each augmented lead. It is referred to immediately below as "the negative pole".

Lead augmented vector right (aVR) has the positive electrode on the right arm. The negative pole is a combination of the left arm electrode and the left leg electrode:

Lead augmented vector left (aVL) has the positive electrode on the left arm. The negative pole is a combination of the right arm electrode and the left leg electrode:

Lead augmented vector foot (aVF) has the positive electrode on the left leg. The negative pole is a combination of the right arm electrode and the left arm electrode:

Together with leads I, II, and III, augmented limb leads aVR, aVL, and aVF form the basis of the hexaxial reference system, which is used to calculate the heart's electrical axis in the frontal plane.

Interpretation of the ECG is ultimately that of pattern recognition. In order to understand the patterns found, it is helpful to understand the theory of what ECGs represent. The theory is rooted in electromagnetics and boils down to the four following points:

• depolarization of the heart towards the positive electrode produces a positive deflection

• depolarization of the heart away from the positive electrode produces a negative deflection

• repolarization of the heart towards the positive electrode produces a negative deflection

• repolarization of the heart away from the positive electrode produces a positive deflection

Thus, the overall direction of depolarization and repolarization produces positive or negative deflection on each lead's trace. For example, depolarizing from right to left would typically produce a positive deflection in lead I if the two vectors point in the same direction. In contrast, that same depolarization would produce minimal deflection in V1 and V2 because the vectors are perpendicular, and this phenomenon is called isoelectric.

Normal rhythm produces four entities - a P wave, a QRS complex, a T wave, and a U wave - that each have a fairly unique pattern.

The P wave represents atrial depolarization.

The QRS complex represents ventricular depolarization.

The T wave represents ventricular repolarization.

The U wave is a further wave on an ECG. It is not always observable. The exact source of the U wave remains unclear. The U wave is thought to represent repolarization of the Purkinje fibers, prolonged re-polarization of mid-myocardial M- cells, after-potentials resulting from mechanical forces in the ventricular wall or repolarization of the papillary muscle.

Changes in the structure of the heart and its surroundings (including blood composition) change the patterns of these four entities.

The U wave is not typically seen and its absence is often generally ignored. Atrial repolarization is typically hidden in the much more prominent QRS complex and normally cannot be seen without additional, specialized electrodes.

In a further embodiment of the present disclosure, the ECG data further comprises time-stamps, such as of registered events. The time stamps may be added to the ECG data and/or during processing of the ECG signals to the ECG data. The time stamps may be added as a result of the electrocardiography device receiving the first subject input. Additionally or alternatively, the first subject input may lead to ECG data obtained during a specific time interval, such as between a predefined time before receiving the first subject input and a predefined time after the receiving the first subject input, is transferred to a second memory.

Leads

A “lead” is an angle of looking at the heart. A standard ECG includes 12 leads, i.e. 12 different angles of orientation in regards to the heart. Each lead provides information about different parts of the heart. A standard ECG typically requires 10 electrodes, carefully positioned at their designated location, in order to provide a 12-lead view.

In a preferred embodiment of the present disclosure, the three ECG electrodes are each positioned towards the left arm (VLA), towards the right arm (VRA), and towards the left leg (VLL) respectively. In a further embodiment of the present disclosure, the six leads comprise or consist of the following:

Electrode positions

The electrical impulse for contraction of the heart stems from the sinus node (located in the right atrium), which acts as the heart’s natural pacemaker. The electrical current is then transmitted via specific pathways throughout the heart, enabling regular contraction and relaxation. This electrical current can be detected on the surface of the body (i.e. the chest wall) via adhesive electrodes.

From the sinus node (sinoatrial node, SA node), the electrical impulse starts by spreading throughout the atria (from right to left). When this happens, the cells lose their internal negativity, a process known as depolarization. The depolarization of the atria causes them to contract.

The electrical current then spreads to the atrioventricular node (AV node), from where it is further transmitted to the intraventricular Septum (separates the left and right ventricles). In order to depolarize the ventricles, the electrical impulse travels through the bundle of His, along the right and left bundle branches (from left to right), and ends at the Purkinje fibers. This process causes depolarization of the ventricles, causing them to contract.

While the ventricles are being depolarized, the atria are regaining their internal electrical negativity, a process known as repolarization. This allows them to relax. Once the ventricles have fully depolarized, they too become repolarized, at which point they relax as well.

The entire process of depolarization and repolarization is depicted on the ECG. The individual events are represented as spikes and waves, each representing a specific part of the cardiac conduction cycle. This visual representation of the conduction system makes it possible to analyze the heart’s electrical activity.

In a further embodiment of the present disclosure, each ECG electrode is configured for detachably connecting to an electrode pad.

A common type of abnormal heart rhythm (arrhythmia) is atrial fibrillation. Typically in atrial fibrillation the heart receives electrical signals that come from outside the SA node causing the atria to contract in a disorganized fashion. The electrical signals also cause the atria to quiver (f ibrillate). With the uncoordinated contraction of the atria and ventricles, the amount of blood pumped out to the body will vary with each heartbeat, with potential serious health effects as a result. The present inventors have further realized how an electrocardiography device should be arranged and placed in order to most efficiently diagnose atrial fibrillation.

Therefore, in a preferred embodiment of the present disclosure, the electrocardiography device is configured to obtain sensitive measurements of the depolarization axis (typically between -30 degrees and +90 degrees for healthy individuals) and/or the QRS complex. The depolarization axis may be obtained by studying the QRS-complex from different angles, such as from lead I, II and AVF. Sensitive measurements of the QRS complex may be obtained by arranging a bipolar lead to be parallel with the depolarization axis. Therefore, it is a preference that the electrocardiography device is arranged such that measurements of the QRS complex may be obtained substantially parallel to the polarization axis.

Preferably, the electrocardiography device is arranged, for example by ECG electrode placement, such that a lead (e.g. a bipolar or an augmented lead) may be formed that is substantially parallel to said depolarization axis. The lead may for example be lead II, arranged at between 0 degree and +90 degrees, such as between +40 degrees and +80 degrees, such as around +60 degrees. This may be obtained by an electrocardiography device comprising three ECG electrodes positioned in an equilateral triangular pattern, typically wherein said device is arranged symmetrically across the sternum, e.g. wherein lead I is substantially horizontal.

The distances and angles between the ECG electrodes are another important factor, for the measurement sensitivity. Therefore, in a further embodiment of the present disclosure, the electrocardiography device is configured such that the ECG electrodes can be positioned, when in use, symmetrically across the sternum. The distances and angles between the ECG electrodes may thereby be configured such that said ECG electrodes may be positioned, when in use, symmetrically across the sternum of the subject. The ECG electrodes may for example be arranged in a triangular pattern, such as an isosceles triangular pattern, or an equilateral triangular pattern. For an electrocardiography device comprising ECG electrodes forming an isosceles pattern, said device is preferably configured to be positioned symmetrically across the sternum. Thereby, it is a preference that the device is arranged such that the two sides of said isosceles pattern of the same length are to be placed symmetrically across the sternum, e.g. extending downwards towards, such as to or beyond, the xiphoid process. Any reference in the present disclosure to positions of ECG electrodes may be applied to the primary ECG electrodes on the housing or to the secondary ECG electrodes of the detachable electrocardiography pad.

Hence, in a preferred embodiment of the present disclosure, the electrocardiography device is arranged such that the two ECG electrodes, i.e. typically the secondary ECG electrodes of the detachable electrocardiography pad, may positioned, symmetrically across the sternum, at (over) the left second intercostal space and at (over) the second right second intercostal space. It is a preference that, at the same time, the third ECG electrode may be positioned centrally of the sternum, such as at (over) xiphoideus. Additionally or alternatively, it may be a preference that one ECG electrode, such as ECG electrode R, is positioned substantially at the sinoatrial node (i.e. to cover at least a part of the sinoatrial node).

In a further embodiment of the present disclosure, the ECG electrodes are located in a substantially equilateral triangular pattern. The ECG electrodes may be located in substantially the same plane, preferably a first plane formed parallel to the first side of the electrocardiography device The ECG electrodes may form a pattern, along the first side, wherein the distance between each electrode is substantially identical. The ECG electrodes may further form a pattern, along the first plane, wherein the angle between each ECG electrode is equal, i.e. an equilateral triangle for the case of three ECG electrodes. In a further embodiment of the present disclosure two of the sides of the pattern formed by the ECG electrodes are of the same length. The pattern may thereby be an isosceles triangle.

In a further embodiment of the present disclosure, the distance between the ECG electrodes are less than around 15 cm. It is a preference that the electrocardiography device is small such that said electrocardiography device is portable and can easily adhere to the skin of the subject for an extended time without discomfort to said subject. In a preferred embodiment the distance between each ECG electrode is less than 15 centimeters, more preferably less than 12 centimeters, yet more preferably less than 8 centimeters. The size of the electrocardiography device may depend on the size of the subject. For example adults may be provided with an electrocardiography device that is larger than an electrocardiography device that is intended for being used by children.

In a further embodiment of the present disclosure, the device is waterproof, for example according to at least IP54, such as IP67. The electrocardiography device may thereby comprise a waterproof enclosure design. It is a further preference that the electrocardiography device can withstand being used while swimming.

In a further embodiment of the present disclosure, the first side of the housing has a substantially triangular shape, and wherein the three ECG electrodes are located in each corner of said first side. In yet a further embodiment of the present disclosure, the first side of the housing has a substantially three bladed shape, and wherein the three ECG electrodes are located in each distal endpoint of said blades. For example, the first side of the housing may have a shape resembling a three bladed propeller, or three bladed boomerang. Said housing may have any shape that has blades extending outwards from a central point. Said blades may furthermore have any shape, regular and/or irregular.

In specific embodiments of the present disclosure, the electrodes (ECG electrodes and/or common mode rejection electrode) are provided as part of an ECG pad (i.e. an adhesive patch comprising multiple ECG electrodes). The portable electrocardiography device may thus further comprise a detachable electrocardiography pad comprising three secondary electrocardiography electrodes arranged in a triangular pattern on a first side of the detachable electrocardiography pad facing a user. The detachable electrocardiography pad may comprise pad connectors arranged on a second side of the detachable electrocardiography pad arranged towards the housing of the portable electrocardiography device and matching an arrangement of the three primary electrocardiography or device connectors of the portable electrocardiography device. The three secondary electrocardiography electrodes are connected to the pad connectors by conductors on or in the detachable electrocardiography pad. The common mode rejection may have a similar arrangement. In one embodiment the detachable electrocardiography pad further comprises a secondary common mode rejection electrode arranged on the first side of the detachable electrocardiography pad arranged towards a user. The secondary common mode rejection electrode may be connected to the primary common mode rejection electrode or device connector on the housing of the portable electrocardiography device by means of a conductor and a pad connector. The present disclosure makes reference to arrangements of electrodes. Such references are generally to be construed as covering either of the primary electrocardiography electrodes or the secondary electrocardiography electrodes. Hence, the secondary electrocardiography electrodes may be arranged in an isosceles triangular pattern or an equilateral triangular pattern. The secondary common mode rejection electrode is located within the triangular pattern of the secondary electrocardiography electrodes, such as wherein the secondary common mode rejection electrode is located at the center of the secondary electrocardiography electrodes.

The description provided herein related to the positioning of the electrodes (e.g. with respects to each other, the electrocardiography device and/or the measurement subject) are irrespective of whether the electrodes are provided as individual electrode pads or as part of an ECG pad. An ECG pad may be easier to apply as the electrodes are preferably already arranged in an ideal relative placement. The positioning of the ECG pad may thereby include to position said pad such that the L and R electrodes are arranged symmetrically around the sternum (i.e. in the left and right second intercostal spaces) while the F electrode is located near, such as at xiphoideus, and/or the common mode rejection electrode is located within the triangular pattern formed by the ECG electrodes, such as substantially in the center of said triangular pattern. In one embodiment the three secondary electrocardiography electrodes comprises a VLA electrode, arranged to be positioned towards the left arm, a VRA electrode arranged to be positioned towards the right arm and a VLL electrode arranged to be positioned towards a leg of a subject, such as a the left leg. The VLA electrode and the VRA electrode may be arranged to be positioned symmetrically across the sternum of a user, preferably at a left and right intercostal space, such as second, respectively. The VLL electrode may be arranged to be positioned along the midsagittal plane of a subject, such as above, near, at or below the xiphoid process, and the VLA electrode and/or the VRA electrode is arranged to be positioned along a transverse plane, such as at the left and right intercostal space respectively, preferably the second left and right intercostal space. This can be achieved by having an arrangement wherein the distance between any of the secondary electrocardiography electrodes is less than 15 cm, preferably between 5 cm and 15 cm more preferably between 7 cm and 12 cm.

The detachable electrocardiography pad may have a generally triangular shape having three corners. “Generally triangular” shall be construed broadly covering also, for example, the heart shape of fig 6A. The generally heart shaped detachable electrocardiography pad may further comprises an extension area extending from the corner corresponding to the VLL electrode, the extension area extending outwardly in a direction from the center of the generally triangular shape. The VLL electrode may be arranged in the extension area. The extension area preferably extends enough to allow a proper placement of the VLL electrode. It may extend, for example, at least 2 cm, more preferably at least 5 cm towards the leg of a user in a wearing position. The extension area preferably has an elongate shape.

The electrodes (i.e. individual electrode patches or multiple electrodes provided as part of a detachable ECG pad) are preferably arranged to hold the housing in position. The ECG pad or the individual patches are arranged to adhere to the measurement subject with an adhesive force that is sufficiently strong to hold the housing in position. The connection between the housing (which holds the electrical components), and the electrode patches and/or the pad may comprise or consist of snap-fit (e.g. button type) connection or a magnetic connection. The pad connectors arranged on the second side of the detachable electrocardiography pad and the primary electrocardiography electrodes or device connectors may also be magnetically connected. Preferably, the magnetic force is in the range from the weight of the housing to twice the weight of the housing. Magnetic connection may for example be advantageous in order to limit the force exerted on the measurement subject. For example, when measuring on infants or small children, connecting a housing with the electrodes through one or more (e.g. one per electrode) snap-fit connections (e.g. button) may require a large force. Contrary to this, a magnetic connection may only need to overcome a smaller force in order to form said connection.

In another embodiment of the present disclosure, the first side of the housing has a substantially rectangular shape. While it is preferred in specific embodiments of the present disclosure that the ECG electrodes are arranged in a triangular pattern, the housing may be provided in any shape. In such an instance, the ECG pads may be provided in a configuration such that they allow for the arrangement of ECG electrodes to form a triangular pattern. For example the ECG pads may be provided with electrical connections to a housing that is remote from one or more of the ECG electrodes. In a preferred embodiment of the present disclosure, the ECG device comprises a single ECG pad comprising ECG electrodes that are arranged such that they form a triangular pattern. Said ECG pad and the ECG housing may be configured to form one or more electrical connections. For example the housing may comprise a number of exposed electrical contacts. The ECG pad may further comprise wirings from the electrodes, such as the ECG electrodes and/or the common mode rejection electrode, to one or more connectors of the ECG pad. The one or more connectors of the ECG pad may be configured to form an electrical connection with the one or more electrical contacts of the housing. Preferably each ECG electrode is, during use, electrically connected to one connector of the ECG pad, and the housing configured to form an electrical connection to each connector of the ECG pad. Preferably, the electrical connectors of the ECG pad are located in a central location of the ECG pad, thereby the ECG housing may comprise a bundled connector, configured for connecting to all electrodes of the ECG pad. It is a preference that the ECG housing is held in place by the connection formed to the ECG pad, thereby the adhesion of the ECG pad to the skin may not only hold the ECG pad in place but furthermore the ECG housing.

In a further embodiment of the present disclosure, the ECG electrodes are configured such that when in use, the L electrode (left arm electrode) is positioned at a left interspace, the R electrode (right arm electrode) is positioned at a right interspace, the F electrode (foot electrode) is positioned centrally at the sternum. In a specific embodiment of the present disclosure, the L electrode is positioned in the second left interspace, the R electrode in the second right interspace and the F electrode centrally near, such as above, at, or below (i.e. in the sagittal plane) the xiphoid process, preferably at the xiphoid process, i.e. wherein the F electrode covers at least a part of the xiphoid process. In yet a further embodiment of the present disclosure, the L electrode is positioned in the third left interspace, the R electrode in the third right interspace and the F electrode centrally near, such as above, at, or below (i.e. in the sagittal plane) the xiphoid process, preferably at the xiphoid process. In yet a further embodiment of the present disclosure, the L electrode is positioned in the fourth left interspace, the R electrode in the fourth right interspace and the F electrode centrally near, such as above, at, or below (i.e. in the sagittal plane) the xiphoid process, preferably at the xiphoid process.

User indication

In a further embodiment of the present disclosure, the device comprises means for indication of battery status and/or lead-off, such as one or more of the electrodes not being properly attached to the skin of the subject. Said means may comprise or consist of a means for providing a visual signal, such as at least one LED. Said means may additionally or alternatively comprise a speaker for providing an audible signal to the subject. Said means may additionally or alternatively comprise means for providing a vibrating alert to the subject. Different types of signals, such as different light colors and/or different sounds may be used for notifying the subject about different events, such as the battery status, the storage status of the first and/or second memory, a lead-off of any of the electrodes.

Method

In a second aspect, the present invention relates to a method for electrocardiographic measurements of a subject. Preferably the method comprises the provision of a portable electrocardiography device. Said portable electrocardiography device may comprise an arrangement of electrodes located on a first plane defined by a first side of a housing of said electrocardiography device. Furthermore, said arrangement of electrodes may consist or comprise of a number of electrodes such as three or four. In a preferred embodiment of the present disclosure, the arrangement of electrodes consists of three ECG electrodes and one Common mode rejection electrode. It is a further preference that the ECG electrodes are located on the first side of the housing of the electrocardiography device. It is a further preference that the three ECG electrodes are located in a triangular pattern. In yet a preferred embodiment of the present disclosure, the electrocardiography device comprises a Common mode rejection electrode that is located in the same plane as the ECG electrodes. In a further preferred embodiment of the present disclosure the Common mode rejection electrode is located within the triangular pattern formed by the ECG electrodes, such as near the center of the triangular pattern formed by the ECG electrodes or substantially in the center of the triangular pattern formed by the ECG electrodes. While the ECG electrodes may form a triangular pattern, it should be noted that the housing may not necessarily be provided in a similar shape. Instead it may be a preference that the housing is provided in a shape that minimizes the area of the first side, and/or minimizes the projected area of the electrocardiography device onto a surface parallel with the first surface. Thereby, the device may be provided in for example a substantially three bladed shape, such as three bladed boomerang and/or a three bladed propeller. The housing of the electrocardiography device may thereby have three arms extending outwards from the centrally located Common mode rejection electrode. Each arm of said three arms may have any length independent of the other arms, and may further extend outward from the central part of the housing at any angle. The special case being wherein each arm forms a 60 degree angle to the adjacent arm, and wherein the length of each arm is identical. In this configuration the pattern of the electrodes may form an equilateral triangle.

In a preferred embodiment of the present disclosure, the method comprises the step of positioning said portable electrocardiography device on the chest of the subject. By positioning the electrocardiography device on the chest of the subject, adhesive electrode pads, located on each electrode, may adhere to the surface of the skin of the subject. The adhesive strength provided of said electrode pads are preferably sufficient to hold the electrocardiography device (e.g. the housing) in place. It is a preference that the electrocardiography device is positioned such that the ECG electrodes are symmetrically located across the chest of the subject.

In yet an embodiment of the present disclosure, the method comprises the step of acquiring ECG signals from the electrodes, such as the three ECG electrodes and the Common mode rejection electrode. The acquisition of ECG signals may be enabled, at least in part, by the use of a processing unit that is in electrical contact with each of the electrodes. Said processing unit may advantageously be configured for processing of the ECG signals into ECG data. Preferably, the electrocardiography device is configured to store said ECG data on a first and/or second memory. It should be noted that the electrocardiography device may be configured in various ways while being able to carry out the presently disclosed method. In a preferred embodiment of the present disclosure, the portable electrocardiography device is defined as described elsewhere herein.

In a further embodiment of the present disclosure, the ECG electrodes are configured such that when in use, the L electrode (left arm electrode) is positioned at a left interspace, the R electrode (right arm electrode) is positioned at a right interspace, the F electrode (foot electrode) is positioned centrally at the sternum. In a specific embodiment of the present disclosure, the L electrode is positioned in the second left interspace, the R electrode in the second right interspace and the F electrode centrally near, such as above, at, or below (i.e. in the sagittal plane) the xiphoid process, preferably at the xiphoid process, i.e. wherein the F electrode covers at least a part of the xiphoid process. In yet a further embodiment of the present disclosure, the L electrode is positioned in the third left interspace, the R electrode in the third right interspace and the F electrode centrally near, such as above, at, or below (i.e. in the sagittal plane) the xiphoid process, preferably at the xiphoid process. In yet a further embodiment of the present disclosure, the L electrode is positioned in the fourth left interspace, the R electrode in the fourth right interspace and the F electrode centrally near, such as above, at, or below (i.e. in the sagittal plane) the xiphoid process, preferably at the xiphoid process.

In a further embodiment of the present disclosure, the distance between the ECG electrodes are less than around 15 cm. It is a preference that the electrocardiography device is small such that said electrocardiography device is portable and can easily adhere to the skin of the subject for an extended time without discomfort to said subject. In a preferred embodiment the distance between each ECG electrode is less than 15 centimeters, more preferably less than 12 centimeters, yet more preferably less than 8 centimeters. The size of the electrocardiography device may depend on the size of the subject. For example adults may be provided with an electrocardiography device that is larger than an electrocardiography device that is intended for being used by children.

A small size of the housing may make the device easier to wear, as a less bulky device may be less noticeable for the measurement subject, which may be important if the device is to be worn for a prolonged amount of time. In addition, a small device may enable easy placement of the device on a measurement subject, for example between breasts. A small size housing and a detachable electrocardiography pad specially adapted for improved placement provide a useful combination of size and functionality.

In a further embodiment of the present disclosure, the ECG electrodes are located in a substantially equilateral triangular pattern. The ECG electrodes may be located in substantially the same plane, preferably a first plane formed parallel to the first side of the electrocardiography device The ECG electrodes may form a pattern, along the first side, wherein the distance between each electrode is substantially identical. The ECG electrodes may further form a pattern, along the first plane, wherein the angle between each ECG electrode is equal, i.e. an equilateral triangle for the case of three ECG electrodes.

In a further embodiment of the present disclosure, the electrocardiography device is configured such that the ECG electrodes can be positioned, when in use, symmetrically across the sternum. The distances and angles between the ECG electrodes may thereby be configured such that said ECG electrodes may be positioned, when in use, symmetrically across the sternum of the subject. Detailed description of drawings

The invention will in the following be described in greater detail with reference to the accompanying drawings. The drawings are exemplary and are intended to illustrate some of the features of the presently disclosed electrocardiography device or method of use thereof, and are not to be construed as limiting to the presently disclosed invention.

Fig. 1 shows an infrastructure for accurate ECG measurement by a portable electrocardiography device. A subject (1) may be provided by for example a medical professional with the portable ECG device (2) and instructed to wear said device for an extended amount of time. The ECG device may be attached to the chest area of the subject by the medical professional. Said ECG device may comprise one or more adhesive ECG pads, for providing electrical contacts with the subject and for adhering to the subject. Thereby, the attachment may be facilitated by the one or more ECG pads. The ECG pad may for example be provided as a single unit comprising three electrodes and further configured for forming electrical connections to contacts on the housing. Preferably the ECG device is attached to the chest area of the subject such that the ECG electrodes are positioned symmetrically across the sternum of the subject. For example electrode L (LA) may be positioned on the left side of the sternum, in an interstitial space. Meanwhile electrode R (RA) may be positioned at the same interstitial space, but on the right hand side. For example the L and R electrode may be positioned in the third left interstitial space and third right interstitial space respectively. At the same time the electrode F (LL) may be positioned centrally over the sternum, for example near or below the xiphoid process. The ECG device may be configured such that the ECG electrodes form an equilateral triangle, given that each side of the triangular pattern formed by said ECG electrodes have the same distance. The device, such as the one or more electrode pad, may further comprise a common mode rejection (CMR) electrode for registering, detection and/or storing of background noise data. The ECG device may comprise means for communication with electrical devices. For example means for (proximal) communication (3) with a proximal personal computation unit (4). The (proximal) means for communication may for example comprise or consist of a Bluetooth chip, for transmitting and receiving communication with a personal computational device (4) having a capability of communication over Bluetooth. Said personal computational device may for example be a smartphone. It is a further preference that at least part of the ECG data is transmitted to the proximal computational device, for subsequently being presented on said personal computational device, to the subject. Furthermore, the ECG device preferably comprises means for communication with a remote server (5), such as means for communication over mobile networks, such as LTE Cat M1 . The ECG device may thereby communicate with an LTE Access point, such as a base station (6), that in turn is connected to a remote server (7), i.e. a cloud server. It should be noted that the ECG device may alternatively or additionally comprise means for communication with the remote server (10). This arrangement thereby allows the ECG device to communicate with the remote server, and transmit ECG data to said remote server. Preferably stored ECG data, such as from a second memory unit of the ECG device may thereby be transmitted to the remote server. The stored ECG data may comprise or consists of a number of leads, preferably two leads, such as Lead I and Lead III, in addition to event data, that subsequently can be used, by the remote server, or a further computational device, for processing of the ECG data in order to obtain a number of additional leads. Preferably the remote server is configured to obtain three bipolar leads, such as Lead I, II, and III and additionally three augmented leads, such as aVR, aVL, and aVF. The remote server may be connected to a LAN of a healthcare provider (8). Healthcare providers may thereafter be provided with the ability to access said data, for example by the use of a WEB application (9), wherein said healthcare provider/medical professional is able to browse and analyze the ECG data. The data may for example be visualized together with annotations of arrhythmias found by the WEB application analysis software. It may be a preference that the ECG device is configured such that said device transmits ECG data to the personal computation device, over for example BLE, upon receiving a second input from a subject. Said second input may for example be a Bluetooth pairing between the personal computation device and the ECG device, or the subject providing an input to the personal computation device and/or the ECG device, such as a press of a button or touchscreen. The ECG device may be configured such that upon receiving the second input, the ECG device transmits at least part of the ECG data, such as Lead I and Lead II, to the personal computation device. The subject may be presented with a visual representation of said transmitted ECG data, such as one or more electrocardiograms. The subject may use this information in order to check that the electrodes are correctly positioned, or a health professional may use said information in order to draw conclusions about a suspected condition of the subject. The ECG device may be configured to periodically transmit ECG data to the remote server, such as when said ECG device is placed in charging mode, wherein the rechargeable electrical batteries of the ECG device are being recharged. Alternatively, or additionally, the ECG device may be configured to communicate with a remote server through the personal computation device. This may be enabled by using the personal computation device for relaying information to the remote server. ECG data may for example be transmitted to the personal computation device over BLE, and thereafter said data may be temporarily stored, before being transmitted to the remote server over a mobile network.

Fig. 2 shows a number of subject interfaces of a smartphone app for obtaining status of the ECG device and registering of abnormal events. Fig. 2A shows a start screen which may be presented to the subject upon opening of the smartphone app. The start screen may present the subject with a number of links, such as to an event screen (11), an ECG screen (12), and potentially to additional subject screens. During the initiation of a recording, the subject may want to ensure that the electrodes are working properly. The subject may enter the ECG screen wherein the subject is presented with a graphical representation of the ECG data, Fig. 2B. In the present example, said graphical representation shows only a single lead (13). The purpose may be to provide the subject with a simple overview that still allows to ensure that the ECG device is able to measure ECG signals properly. For this purpose there may not be a need to display multiple leads to the subject. As disclosed elsewhere herein, the ECG device may start transmitting ECG data, such as the mentioned single lead, to the smartphone, or other type of computational device, upon receiving a second subject input. Said second subject input may for example be provided by the smartphone upon the subject entering the testing interface, wherein the subject is to be presented with the at least one lead. Said ECG screen may alternatively or additionally be presented to the subject of the ECG device upon providing the ECG device with a second input, such as pairing of the ECG device and the personal computation device. Alternatively, or additionally the second subject input may be a signal generated by the press of a button or a touch screen, on the ECG device and/or the personal computation device. Upon receiving the second input, the ECG device transmits at least part of ECG data to the personal computation device. The ECG data transmitted to the personal computation device may be down sampled, and may thereby have a lower resolution. Said transmitted ECG data may comprise the momentarily obtained ECG data, such as the momentarily processed ECG signals. The subject interface may provide the subject with a graphical representation of a number of the leads, preferably at least two. In that case the personal computation device may not be required to compute additional leads. For the remote server, it may however be a preference that said server, or another computational device connected thereto, has the capabilities to compute additional leads, than the leads transmitted to the remote server, such as Lead I and Lead III. Thereby, the remote server, or the computational device connected thereto may be configured to compute bipolar leads, e.g. Lead I, II, and III, and additionally a number of augmented leads such as aVL, aVF, aVR.

Further, the home screen may allow the subject to enter the event screen, Fig. 2C, wherein the subject may be provided with the ability to register events (14), for example by selecting any of a number of predefined events. The events and/or the predefined events may comprise for example fainting, dizziness, chest pain, high pulse, low pulse, palpitation, and/or near fainting. Upon registering of an event the ECG device may be configured to add time points of said registered event to a memory of the ECG device, such as the first memory. Additionally, or alternatively the registering of an event may lead to an interval of the ECG data being transferred from a first memory onto a secondary memory, such as from a first memory unit to a secondary memory unit. The transferred ECG data may comprise ECG data obtained by the ECG device during an interval comprising the time point for registering of the event. For example the interval may be between a predefined time before the registering of the event and a predefined time after the registering of the event. The transferred ECG data may comprise the Leads, such as Leads I and III obtained during this interval, in addition to additional information, event information, provided during registering of the event, such as the time point of the event, the type of event, text-based comments about the event, and/or audio recordings about the event. Said event information may comprise information related to said events, such as information related to what the subject was experiencing when said subject noticed the abnormal event, what activity said subject was carrying out, and/or speculations of the cause of the event.

Additionally, the smartphone app may comprise a screen wherein registered events are presented to the subject, a registered event screen, Fig. 2D. This screen may be configured such that the subject is capable of accessing, editing and/or modifying information that is connected to each registered event, in addition to accessing the recordings of each event, for example by selecting one of the registered events (15). Further, the smartphone app may comprise an information screen, Fig. 2E, wherein the subject is provided with registered information related to the current profile (16), i.e. information about the present subject of the ECG device, such as the name, social security number, and contact info, and device information (17), such as battery status, device model and memory status.

Fig. 3 shows a subject interface of a web application for use by a medical professional comprising ECG data obtained during an extended amount of time. Fig. 3A shows an initial interface providing an overview of information about the subject (18), and events registered by the subject, i.e. an event log (19). The medical professional may for example be provided with the name, the social security number, the doctor, the type of device of said subject. Furthermore, the interface may allow the medical professional to access each registered event, such as at least part of the associated ECG data. This may be presented to the medical professional in a secondary interface, Fig. 3B, wherein multiple leads are presented, preferably six leads, such as Leads I (21), Lead II (22), Lead III (23), augmented lead aVR (24), augmented lead aVF (25), and augmented lead aVL (26). The remote server may have processed the ECG data comprising typically two leads into six leads. Additional filters and data optimizations may further have been applied to the ECG data. This information is provided in the secondary interface to the medical professional who can identify any abnormalities related to the electrical activity of the heart, such that conclusions may be drawn about the suspected medical conditions of the subject. Additional statistics about each event are preferably present in the same secondary screen, such as the average heart rate, the longest QRS complex, the average QRS complex interval, the average RR interval, the average QT interval and the longest PQ interval (27).

Fig. 4 shows a schematic illustration of the ECG device, shown from the first side, comprising a detachable electrocardiography pad (28) and a housing (29). The ECG device here comprises a single detachable electrocardiography pad wherein the detachable electrocardiography pad comprises both the secondary ECG electrodes (30) and the secondary common mode rejection electrode (31). In a specific embodiment of the present disclosure, the housing comprises a number of primary ECG electrodes (32) for providing electrical signals to the electrical circuitry of the ECG housing. Electrical conductors (33) may be provided as part of the detachable electrocardiography pad for forming electrical connections between the electrodes, such as the ECG electrodes and/or the common mode rejection electrode, and the primary ECG electrodes of the housing (32). The detachable electrocardiography pad is here shown as semitransparent for illustrative purposes, thereby showing a typical arrangement of the detachable electrocardiography pad pad and the ECG housing. The first side of the electrocardiography device (34) is the side that is to face the subject, during use. The first side of the electrocardiography device may coincide with the first side of the housing, if the housing comprises the electrodes. However, if the electrodes are provided as part of a separate ECG pad, said electrodes may be positioned between the ECG housing and the subject.

Fig. 5 shows block diagrams describing the electrical circuitry of the ECG device for processing of the ECG signal. Among other features of the circuit, the processing of the signal to acquire the right leg drive. The common mode rejection electrode may be driven by the RLD to counter any differences between the reference voltage and the detected common-mode level. Thereby acting to reduce the amount of power-line common-mode interference. The figure shows a number of inputs (IN1-IN6) that are filtered by an electromagnetic interference filter (EMI). Typically, only three in-channels are used, such as IN1 , IN2, and IN3, each being connected to an electrode and thereby providing the ECG signal of said each electrode, for example IN1 may be connected to RA, IN2 may be connected to LA, and IN3 may be connected to LL. Thereby each in-channel is provided the ECG signal from each respective ECG electrode. The in-channels (IN1 , IN2, and IN3) may be used in a driven right leg circuit in order to eliminate measurement noise by actively cancelling the common-mode interference. These in signals are thereby used to derive an inverted signal of the common-mode interference. The in signals are provided to a Common-Mode Detector to measure the common-mode of the system by averaging the voltage of input pins IN1 , IN2 and IN3, and uses this signal in the right-leg drive feedback circuit. The output of the RLD amplifier is connected to RL through IN4 to drive the common-mode of the system. Wilson reference generator circuit. First, said inputs are routed to a Wilson reference electrode amplifier that filters out the common mode interference. This may for example be the sum of Lead I, Lead III, -Lead II. Given the conventional notation, a non-zero sum of the above equation is expected to represent the common mode interference. By routing the output of the Wilson reference electrode amplifier (Wilson ref.) through the Wilson reference output (WCT), to the Right-leg drive amplifier negative input (RLDINV), the RLD amplifier (RLD Amp.) produces an inverted common mode interference signal that is output to the Right-leg drive amplifier output (RLDOUT). This inverted common mode interference signal is thereafter connected to the common mode rejection electrode for actively cancelling of the common-mode interference. Fig. 6 shows a schematic illustration of a detachable electrocardiography pad (Fig. 6A- B), a housing (Fig. 6C) for an electrocardiography device, and a system comprising a housing and a detachable electrocardiography pad (Fig. 6D), according to an embodiment of the present disclosure. In this example, the housing and the ECG pad have a triangular shape, and they are arranged such that the second electrodes, preferably also the first electrodes, are arranged in a triangular shape. The triangular shape is shown such that is points downwards, i.e. the two upper electrodes (62, 63) are in a horizontal plane, while the third secondary electrode (64) are arranged below. However, the arrangement may also be such that the electrodes points upwards, with the same technical effects. For example, that this arrangement enable more sensitive ECG measurements, as the electrodes may connect to areas of a person with a low amount of tissue, for example between the breasts. Preferably Fig. 6A shows a first side of the detachable electrocardiography pad (61) that is to face the subject during use. This first side of the ECG pad comprises three secondary ECG electrodes (62, 63, 64) arranged in a triangular pattern. A first electrode (62) is arranged to be positioned in the left second intercostal space, a second electrode (63) is arranged to be positioned in the right second intercostal space, and a third electrode (64) is arranged to be positioned at xiphoideus (64). The detachable electrocardiography pad (61) further comprises a secondary common mode rejection electrode (65), located within the triangular pattern formed by the secondary ECG electrodes. It can be seen that the detachable electrocardiography pad comprises a main body (66) having a tapered end (67). The main body may have any kind of shape, such as triangular, however it is a preference that it has a tapered end and/or an extension area. The shape may also be generally triangular, which shall be construed broadly covering also, for example, the heart shape of fig 6A, further comprising an extension area (76) extending from the lower corner of the triangular shape. As can be seen the third electrode (64), i.e. the VLL electrode, may be positioned in in the extension area (76). It is a further preference that the main body and/or an extension area is arranged to be positioned symmetrically across the sternum, preferably such that the main body and/or elongated part may be positioned between breasts. In this position the secondary ECG electrodes may be arranged to make contact with the left and right second intercostal spaces and the xiphoideus. An ECG device that is arranged to form such a contact with a subject may allow for sensitive measurements as breast tissue acts to decrease the measurement sensitivity. Consequently, in order to allow for sensitive measurements, the ECG device is preferably arranged such that the three secondary ECG electrodes may be arranged to be positioned at a left and right intercostal space (e.g. second left and right intercostal space), and the xiphoideus, the main body of the ECG pad may be required to have a tapered end or an extension, e.g. towards xiphoideus. It is a further preference that an extension area (76) extends downwards, such as along the sternum, from the tapered end of the main body. It is a preference that an ECG electrode is located on the extending section, and said ECG electrode is arranged to make contact with the skin at xiphoideus (such as when the other two secondary ECG electrodes are positioned at the second left and right intercostal spaces), alternatively the ECG electrode of the extending section may be arranged to be located above or below xiphoideus. The elongated part is preferably arranged to extend vertically during use and preferably has an oblong shape wherein the width (i.e. the horizontal part during use) is less than 10 cm, more preferably less than 7 cm ,most preferably less than 5 cm. At the same time, the length (i.e. the vertical size during use) is at least 5 cm, more preferably at least 7 cm, most preferably at least 10 cm. It is a further preference that the sides of the tapered end of the secondary ECG pad (61) are concave. The concave sides (68), may be symmetrical on each side of the ECG pad. In this way, the ECG pad may be positioned between a subject’s breasts. Thus, the first and the second ECG electrodes may overlap in position. Alternatively, the electrodes may be arranged such that at least the second electrodes have a triangular pattern, and wherein the first electrode is arranged on the housing, facing the ECG pad (61). Thus, the lower second electrode (64) may require an electrical conductor, connecting the lower first electrode (70) and the lower second electrode (64). In this way, the lower second electrode may be positioned in a way as to provide more sensitive ECG measurements. Typically, the housing does not cover the lower second electrode (64), but it is provided on the extension area (76). Alternatively, the ECG pad may be provided with two lower second electrodes, provided on a single elongated part (76), or alternatively on multiple, such as two, elongated parts (76). In this way, multiple, such as two, secondary electrodes may be positioned outside the housing, in hard-to-reach areas of a person. Preferably, the ECG device, i.e. the ECG pad, comprises at least one extending section, and the extending section comprises at least one second electrode that is connected to a first electrode located on the back-side of the housing. Alternatively, the ECG device, i.e. the ECG pad, comprises at least one extending section, or multiple, such as two, and the extending section(s) comprises multiple second electrodes, such as two, that is each connected to a first electrode located on the back-side of the housing.

Fig. 6B shows the second side of the ECG pad (61 ), i.e. the side that, during use, is to face away from the subject and towards the housing. This side may comprise four snap-fit connectors (i.e. male or female). Three first snap fit connectors (70) that are to form a connection with the secondary ECG electrodes through an electrical conductor (71 ). The snap-fit connector and the electrical conductor (71) are formed in a conductive material, so as to lead signals between the subject and the housing. Thereby, at one end the electrical conductors (71) are in electrical contact with the snap-fit connectors (70), and at the other end said electrical connectors are in electrical contact with the secondary ECG electrodes. Other means for connecting the electrodes (i.e. the ECG electrodes and/or the common mode rejection electrode) with the housing (e.g. electrical components of the housing such as the battery, processing unit and/or memory) are possible as disclosed elsewhere herein. For example, magnetic connectors, possible even magnetic snap-fit connectors, may be used, that both provide an electrical connection and a magnetic retention force. In this case, an electrical connection may be formed separate from the magnetic connection. As stated above the dimensions of the housing, the detachable electrocardiography pad, including the extension area, and the primary and secondary ECG electrodes may each play a role in how the device and electrodes are arranged on a user. Example of preferred distances between the secondary electrodes in fig. 6A are: 62-63: 70-110 mm, 62-64: 80-120 mm, 63-64: 80-120 mm. In fig. 6B, in which the snap-fit connectors (70) match the device connectors of the housing. Examples of preferred distances include: upper left conductor (71): 10-30 mm, upper right conductor (71): 10-30 mm, conductor along extension area (76): 20-60 mm.

Fig. 6C shows the housing seen from the side that is to make contact with a subject during use. This side of the housing has a corresponding set of device connectors or primary ECG electrodes (73, 74), in order to engage with the pad connectors of the ECG pad. For example the housing may have four female snap-fit connectors while the ECG pad may have four male snap-fit connectors (73 - for ECG electrodes, 74 - for common mode rejection electrode). Alternatively, or in combination, the housing may have corresponding magnetic connectors as disclosed elsewhere herein, in such an instance the electrical connection may be formed separate from the means for forming a magnetic connection. The housing has a shape that, to a large extent, corresponds to the main body of the ECG pad. Similar to the detachable electrocardiography pad, the housing preferably has a tapered end (75), and said tapered end is preferably arranged to extend downwards along sternum during use (i.e. when the detachable electrocardiography pad is connected to a subject and when the housing is connected to said detachable electrocardiography pad. The sides of said tapered end of the housing may be concave (for example similar to the detachable electrocardiography pad), such as to fit between a subject’s breasts. The housing may have any type of shape, preferably wherein an end is tapered, such as a triangular shape or a heart shape. It is a further preference that, when the housing is connected to the detachable electrocardiography pad, the housing covers the main body of the detachable electrocardiography pad. Preferably, the detachable electrocardiography pad, more specifically the extension area (76), protrudes at least 2 cm, more preferably at least 5 cm beyond the edge of the ECG housing This may also be seen in Fig. 6D, showing an electrocardiography device wherein the housing (67) covers the main body of the ECG pad (61), while the extension area (76) extends beyond the edge of the edge of the housing. A conductor (71 ) can be seen that is arranged to form an electrical connection between the housing and the electrode. This ensure that the electrodes are capable of being positioned at locations that allows for sensitive ECG measurements, specifically related to atrial fibrillation, e.g. of the QRS wave and/or the depolarization axis.

Items

1 . A portable electrocardiography device comprising :

• an arrangement of electrodes or device connectors located on a first plane defined by a first side of the portable electrocardiography device, including: o three primary electrocardiography electrodes or device connectors arranged in a triangular pattern; o a primary common mode rejection electrode or connector; and

• a housing comprising: o a power source, such as a battery; and o a processing unit in electrical communication with the electrodes or device connectors, said processing unit configured for receiving an electrocardiography signal from each electrode or device connector and processing the electrocardiography signals into electrocardiography data; and/or

A portable electrocardiography device comprising:

• a housing;

• a battery;

• an arrangement of electrodes located on a first plane defined by a first side of the housing, including:

• three ECG electrodes arranged in a triangular pattern;

• a common mode rejection electrode located in the center of the triangular pattern; and

• a processing unit in electrical communication with the electrodes, said processing unit configured for receiving an ECG signal from each electrode and processing the ECG signals into ECG data.

Communication means

2. The portable electrocardiography device according to any one of the preceding items, wherein said device comprises means for wireless communication, such as 4G LTE, 5G and/or Bluetooth Low Energy.

3. The portable electrocardiography device according to any one of the preceding items, wherein said device comprises means for wireless communication with a cloud-based server and/or a personal computing device, such as a smartphone. 4. The portable electrocardiography device according to any one of the preceding items, wherein the device is configured to, upon receiving a first subject input, store ECG data and/or ECG signals obtained during a recording interval, said recording interval being defined by a predetermined time before receiving said first subject input and a predetermined time after receiving said first subject input, such as on a second memory.

5. The portable electrocardiography device according to any one of the preceding items, wherein said ECG data and/or ECG signals are stored on a second memory of said portable electrocardiography device.

6. The portable electrocardiography device according to any one of the preceding items, wherein said device is configured to, upon receiving a second subject input, continuously transmit ECG data to the personal computing device, such as low- resolution ECG data for ensuring correct placement of the electrodes.

7. The portable electrocardiography device according to any one of the preceding items, wherein said device is configured to periodically, such as upon recharging of the battery, transmit stored ECG data, such as from the secondary memory, to the cloud-based server.

Electrical components

8. The portable electrocardiography device according to any one of the preceding items, wherein the device is configured to measure the Wilson’s central terminal, such as continuously measuring.

9. The portable electrocardiography device according to any one of the preceding items, wherein the device is configured to invert the Wilson’s central terminal and apply it to the common mode rejection electrode.

10. The portable electrocardiography device according to any one of the preceding items, wherein the device is configured to derive ECG signals from the ECG electrodes to an inverted common-mode interference signal, wherein the inverted common-mode interference signal is applied to the common mode rejection electrode. 11 . The portable electrocardiography device according to item 10, comprising a Wilson reference generator circuit, wherein the ECG signals from the ECG electrodes are connected to the Wilson reference generator circuit, and wherein the Wilson reference generator circuit is configured to a common-mode interference signal.

12. The portable electrocardiography device according to item 11 , further comprising an inverter stage, wherein the inverter stage is configured to invert the commonmode interference signal to the inverted common-mode interference signal.

13. The portable electrocardiography device according to any one of items 10-12, wherein the inverted common-mode interference signal is connected to the common mode rejection electrode to actively cancel common-mode interference.

14. The portable electrocardiography device according to any one of the preceding items, wherein the device is configured for continuously receiving ECG signals and/or processing ECG signals into ECG data.

15. The portable electrocardiography device according to any one of the preceding items, wherein the device is configured to automatically and continuously receive and/or process ECG signals upon connecting each ECG electrode to an electrode pad.

16. The portable electrocardiography device according to any one of the preceding items, wherein the device comprises a first memory for loop recording of ECG data.

17. The portable electrocardiography device according to any one of the preceding items, wherein the device is configured for loop recording of ECG data, such as on the first memory.

18. The portable electrocardiography device according to any one of the preceding items, wherein the device is configured to receive the first subject input from the personal computation device and/or input means located on said electrocardiography device, such as a button. 19. The portable electrocardiography device according to any one of the preceding items, wherein the electrocardiography device is capable of being used for at least 4 days without replacing or recharging the battery.

Data processing

20. The portable electrocardiography device according to any one of the preceding items, wherein the ECG data comprises or consists of two stored ECG leads, such as Lead I and Lead III.

21 . The portable electrocardiography device according to any one of the preceding items, wherein the ECG data further comprises time-stamps, such as of registered events.

22. The portable electrocardiography device according to any one of the preceding items, wherein the two stored ECG leads are selected such that they can be used to calculate six ECG leads.

23. The portable electrocardiography device according to any one of the preceding items, wherein the six leads comprise or consist the following:

24. The portable electrocardiography device according to any one of the preceding items, wherein the device is configured to derive electrocardiography signals from the primary electrocardiography electrodes to an inverted common-mode interference signal, wherein the inverted common-mode interference signal is applied to the primary common mode rejection electrode.

25. The portable electrocardiography device according to item 24, comprising a Common-mode detector circuit, wherein the electrocardiography signals from the primary electrocardiography electrodes are connected to the Common-mode detector circuit, and wherein the Common-mode detector circuit is configured to output a common-mode interference signal.

26. The portable electrocardiography device according to item 25, further comprising an inverter stage, wherein the inverter stage is configured to invert the commonmode interference signal to the inverted common-mode interference signal.

27. The portable electrocardiography device according to any one of items 24-26, wherein the inverted common-mode interference signal is connected to the common mode rejection electrode to actively cancel common-mode interference.

Electrode positions

28. The portable electrocardiography device according to any one of the preceding items, wherein each ECG electrode is configured for detachably connecting to an electrode pad.

29. The portable electrocardiography device according to any one of the preceding items, wherein the housing of the device is substantially triangular and wherein the three electrocardiography electrodes are located at, or towards, each corner of the housing

30. The portable electrocardiography device according to any one of the preceding claims, wherein the housing has a first side for facing the subject during use, said first side of the housing having a substantially triangular shape, and wherein the three electrocardiography electrodes are located in each corner of said first side of the housing.

31 . The portable electrocardiography device according to any one of the preceding items, wherein the device is configured to, when in use, be positioned symmetrically across the sternum.

32. The portable electrocardiography device according to any one of the preceding items, wherein the ECG electrodes are located in a substantially equilateral triangular pattern. 33. The portable electrocardiography device according to any one of the preceding items, wherein the distance between the ECG electrodes are less than around 15 cm

34. The portable electrocardiography device according to any one of the preceding items, wherein said device is waterproof.

35. The portable electrocardiography device according to any one of the preceding items, wherein the first side of the housing has a substantially triangular shape, and wherein the three ECG electrodes are located in each corner of said first side.

36. The portable electrocardiography device according to any one of the preceding items, wherein the ECG electrodes are configured such that they may be positioned, respectively, at the locations defined in the table below:

37. The portable electrocardiography device according to any one of the preceding items, wherein said electrocardiography device is configured such that the housing is fixed in position, with respect to the subject, by a connection to at least one electrocardiography pad.

38. The portable electrocardiography device according to any one of the preceding items, wherein the electrocardiography device is configured to, when in use, be positioned symmetrically across the sternum.

39. The portable electrocardiography device according to any one of the preceding items, wherein the primary electrocardiography electrodes are arranged in a substantially equilateral triangular pattern.

40. The portable electrocardiography device according to any one of the preceding items, wherein the three primary electrocardiography electrodes are arranged to attach symmetrically across the sternum of the subject at: the second left interspace, the second right interspace, and at xiphoideus, respectively; and wherein the common mode rejection electrode is located within the triangular pattern. 1 . The portable electrocardiography device according to any one of the preceding items, wherein the pad connectors arranged on the second side of the detachable electrocardiography pad and the primary electrocardiography electrodes or device connectors are magnetically connected. 2. The portable electrocardiography device according to item 41 , wherein the housing is attached to, and/or retained by, the subject by the pad connectors arranged on the second side of the detachable electrocardiography pad by a magnetic force at least equal to the weight of the housing. 3. The portable electrocardiography device according to item 43, wherein the magnetic force is in the range from the weight of the housing to twice the weight of the housing. 4. The portable electrocardiography device according to and any one of the preceding items, wherein the pad connectors arranged on the second side of the detachable electrocardiography pad and the device connectors are snap-fit buttons. 5. The portable electrocardiography device according to any one of the preceding items, further comprising individual attachable electrocardiography pads connected to the primary electrocardiography electrodes or device connectors and an individual primary common mode rejection electrode pad connected to the primary common mode rejection electrode or connector. 6. The portable electrocardiography device according to any one of the preceding items, wherein the detachable electrocardiography pad is a patch.

User indication 7. The portable electrocardiography device according to any one of the preceding items, wherein said device comprises means for indication of battery status and/or lead-off, such as at least one LED. Method

48. A method for electrocardiographic measurements of an subject, comprising:

• providing a portable electrocardiography device comprising an arrangement of electrodes located on a first plane defined by a first side of the housing, including: i. three ECG electrodes arranged in a triangular pattern; and ii. a common mode rejection electrode located in the center of the triangular pattern;

• positioning said portable electrocardiography device on the chest of said subject; and

• acquiring ECG signals from said electrodes; thereby performing electrocardiographic measurements of the subject.

49. The method according to item 48, wherein the portable electrocardiography device is defined according to any of item 0-47.

50. The method according to any one of items 48-49, wherein the electrodes of the portable electrocardiography device are positioned, on said subject, respectively, at the second left interspace, the second right interspace and at or below the xiphoid process.

51 . The method according to any one of items 48-50, wherein the electrodes are positioned, on said subject, with a spacing between any one of the electrodes that is less than around 15 cm.

52. The method according to any one of items 48-51 , wherein the electrodes are positioned, on said subject, according to an equilateral triangle.

53. The method according to any one of items 48-52, wherein the electrodes are positioned, on said subject, symmetrically across the sternum.

54. The method according to any one of items 48-53, wherein the electrocardiography device comprises three primary electrocardiography electrodes comprising a VLL electrode, a VLA electrode and a VRA electrode, and wherein the VLL electrode is positioned, on the subject, along the midsagittal plane of a subject, such as at the xiphoid process of the subject, and the VLA electrode and/or the VRA electrode is arranged to be positioned along a transverse plane of the subject. The method according to item 54, wherein the VLL electrode is positioned at the xiphoid process of the subject, and the VLA and the VRA electrodes are positioned symmetrically across the sternum, at a left and right intercostal space respectively. The method according to item 55, wherein the VLA electrode and the VRA electrode are positioned at the second left and second right intercostal space respectively. The method according to any one of items 48-56, wherein the portable electrocardiography device further comprises a detachable electrocardiography pad comprising three secondary electrocardiography electrodes arranged in a triangular pattern on a first side of the detachable electrocardiography pad arranged towards a user, wherein the detachable electrocardiography pad further comprises an extension area extending from a VLL electrode and wherein said extension area is positioned to extend downwards, away from the housing, between the breasts of the subject.