Identification of Arrhythmias With One-time ECG

The research aims to solve the following medical problems:

1. Identifying and defining the type of atrial fibrillation is problematic due to its spontaneous occurrence and latency.
2. Measurement devices for screening atrial fibrillation are poorly available.

The main research questions are:

1. Can a single-lead ECG measurement be used to detect arrhythmias
2. Find out the measurement locations (ECG leads) for single-lead ECG self-monitoring and evaluate the impact of measurement locations on usability and signal quality.
3. Find out the measurement locations for single-lead ECG monitoring when the measurement is performed by another person (nurse or relative) and evaluate the impact of measurement locations on usability and signal quality.
4. Find out the reliability of single-lead ECG measurement for the identification of atrial fibrillation.
5. Find out the reliability of single-lead ECG measurement for identification of rapid (tachycardia) and slow heart rate (bradycardia).
6. Can a wristband based on optical pulse registration be able to obtain reliable information about arrhythmias
7. Find out the usability of the pulse wristband for the identification of atrial fibrillation.
8. Find out the usability of the pulse wristband for the identification of rapid (tachycardia) and slow heart rate (bradycardia).

The purpose of the study's method development is to evaluate reliability of heart rate measurement in single-lead ECG and pulse wave measurement with healthy and patients with heart problems. The study develops computing methods based on lightweight measurement technology to reliably identify the most common cardiac arrhythmia, atrial fibrillation. The diagnosis and treatment of atrial fibrillation are decisive factors for preventing strokes.

Research patients have already undergone a 12-channel clinical ECG registration included in the normal treatment process. This 12-channel ECG is used for the identification of patients suitable for research and dividing to subgroups (normal rhythm, atrial fibrillation, rapid or slow rhythm).

In actual study measurements, a Holter-ECG device is attached on patient's chest using five wet electrodes to be used as golden standard for rhythm monitoring. The lightweight measurement methods are compared with the result of the Holter-ECG registration. In addition, photopletysmogram is placed on patient's wrist for PPG registration. Figure 1 shows illustrative examples of the study's measurements.

The researcher measures one minute recordings from two different measuring positions (flank and chest) with a one-time ECG measuring device. After that, the patient performs one minute self-monitoring measurements with one-time ECG device from the all three positions (thumbs, flank and chest) and also from the chest with jewel-ECG.

The study compares the ability of these lightweight measurement methods to detect different heart rhythms compared to the Holter registration.

The devices used for the measurement are:

1. Faros 360 EKG sensor with wet electrodes (figure 1, device 1) (Mega Elektroniikka, http://www.megaemg.com/ Kuopio Suomi). Faros 360 Holter is CE and FDA 510(k) cleared class 2a medical device, which is attached to the patient's chest with five single-use wet electrodes.
2. Suunto Movesense one-time ECG device (Suunto Oy, http://www.suunto.com Vantaa Suomi). Movesense is CE cleared consumer device, which is used with two dy electrodes to the ECG measurement (Figure 1 devices 2 and 3). Movesense case; jewel and one-time ECG case.
3. In the previous study (Afib24h), Valvira was reported and the research received permission for the clinical device study (Movesense + chest strap combination).
4. For this study, Valira is reported for a clinical device study (Movesense + one-time ECG device combination)
5. Empatica E4 activity bracelet (Empatica Ltd http://www.empatica.com Milan Italia), which is CE cleared consumer device. Empatica E4 is also a photopletysmogram, which measures optically the amount of blood circulating in the blood vessel (Figure 1 device 4).
6. Samsung Gear S3 wearable (Samsung Electronics, Co., Ltd., www.samsung.com Soul Etelä-Korea) which is CE cleared consumer device. Gear S3 is also a photopletysmogram, which measures optically the amount of blood circulating in the blood vessel.

The researcher attaches devices to the patient. After that, the researcher starts a 10-minute registration with Faros 360 (device 1) and Empatica E4 (device 4) devices. During a 10-minute measurement, the researcher measures one minute recordings from two different measuring positions with the Movesense ECG (device 2) 1. from the chest, sternum perpendicularly 2. from the chest, along the sternum. The patient then carries out one minute self-monitoring measurements 1. from the chest, sternum perpendicularly 2. from the chest, along the sternum 3. from the lower part of the flank 4. from thumbs and 5. from the chest with a jewel-ECG.

Heart rate detection by ECG measurement is most commonly done by the detection of QRS complexes. Numerous of these QRS detectors have been developed in recent decades. ECG measurement with dry electrodes involves considerably more movement disturbances, compared to the wet electrode measurements, as even the small movements of the device induce major changes to the ECG signal. In addition, especially when using thumbs as a measurement points, the EMG noise from the muscles is remarkably high compared to the wet electrode measurements.

This project utilizes the methods developed in the earlier mobile-ECG-project for noise and QRS detection to allow reliably detection of QRS complexes and heart rate irregularities in the dry electrode measurements.

In this study, the previously developed heart rate detection methods are validated by study's measurements of normal sinus rhythm, atrial fibrillation, and slow (bradycardia) and rapid (tachycardia) heart rate.

This study examines capability of pulse detection in detection of atrial fibrillation. The photopletysmogram measures the absorption of light in the tissue. The absorption of light into the blood is greater than the absorption into the surrounding tissue. When the heart beats, capillaries expand and contract based on blood volume changes. Photopletysmography allows the heart rate measurement by detecting changes in absorption.

Photopletysmgram, like a mobile-ECG device, is particularly sensitive to motion, even the small motion of led/photodiode induce major change in light intensity.

Also, physiological changes cause a disturbance in heart rate measurement, for example, as the vascular elasticity changes, the pulse time changes, resulting a disturbance in measurement.

Unlike the high-frequency pierced QRS complex, the pulse wave is a low-frequency up-down variation, which causes its own challenges for accurate heart rate measurement.

The atriums work insufficiently in atrial fibrillation therefore the ventricles are not completely filled with blood. In addition, atrial fibrillation causes the irregular conduction of impulses from atriums to the ventricles leading to pulse irregularity. The amount of blood pumped varies from one stroke to stroke, which makes the pulse wave detection challenging.

This project develops methods for accurate heart rate measurement from a pulse wave series.

The method development aims to take account of disturbances due to the motion of the meter, pulse wave irregularities typical of atrial fibrillation, and the challenges of slow (bradycardia) and rapid (tachycardia) heart rate detection.

The main goal of the method development is to determine the pulse so precisely that pulse irregularity due to atrial fibrillation can be distinguished from normal sinus rhythm and reliably detect rapid and slow heart rhythms.

In atrial fibrillation, electrical impulses conduct randomly to the ventricles, causing the heart rate to be irregular and uneven. A large campaign by the Heart Association "Feel your pulse - prevent the stroke" is based on heart rate or pulse recognition. Pulse recognition is of course the cheapest method to detect atrial fibrillation, but this method produces a large number of false positives. By ECG measurement, the detection of atrial fibrillation is much more reliable. Automated atrial fibrillation detection algorithms have been developed for this purpose.

Identification of the atrium activation in long-term Holter-ECG measurements is generally very challenging due to the poor signal-noise-ratio (motion, muscle-artefacts and partly overlapping much stronger ventricular activity). For this reason, most atrial fibrillation detection algorithms are based on the identification of pulse irregularity. For parametrization of the irregularity of the heart rate (RR-interval) has been introduced several relatively simple but reliable time-level methods. As an example, A RdR-based method wherein the RR intervals (heart rate) are represented as a function of consecutive RR interval changes (heart rate change) (Lian et al. 2011). The RdR-graph defines the fragmentation of the pattern resulting from irregular heart rate changes. In addition, there are methods that estimate RR time series internal coherence (Lee et al. 2011). Various nonlinear methods have also been introduced to parametrization of the heart rate variation, enabling the dynamics of the heart rate variation to be described more broadly (without limitation of the linearity assumption). One class of nonlinear methods are different entropy quantities, these are particularly interesting for the identification of atrial fibrillation and the irregular heart rate. Entropy quantities can be used to estimate the regularity and predictability of the RR time series. Typically, the reliable calculation of the entropy quantities requires a relatively long measurement time, but also entropy quantities that are suitable for the analysis of short measurements have been introduced (Lake \& Moorman 2011).

This research project develops new atrial fibrillation detection algorithms for the mobile-ECG measurement and pulse wave measurement on the basis of already existing methods. Algorithms must take into account atrial and ventricular premature complexes. Ignoring of these increases the irregularity of the RR time series and thus increases the number of false positive atrial fibrillation.