Data-Driven ECG Denoising Techniques for Characterising Bipolar Lead Sets along the Left Arm in Wearable Long-Term Heart Rhythm Monitoring

Abstract

Abnormal heart rhythms (arrhythmias) are a major cause of cardiovascular disease and death in Europe. Sudden cardiac death accounts for 50% of cardiac mortality in developed countries; ventricular tachycardia or ventricular fibrillation is the most common underlying arrhythmia. In the ambulatory population, atrial fibrillation is the most common arrhythmia and is associated with an increased risk of stroke and heart failure, particularly in an aging population. Early detection of arrhythmias allows appropriate intervention, reducing disability and death. However, in the early stages of disease arrhythmias may be transient, lasting only a few seconds, and are thus difficult to detect. This work addresses the problem of extracting the far-field heart electrogram signal from noise components, as recorded in bipolar leads along the left arm, using a data driven ECG (electrocardiogram) denoising algorithm based on ensemble empirical mode decomposition (EEMD) methods to enable continuous non-invasive monitoring of heart rhythm for long periods of time using a wrist or arm wearable device with advanced biopotential sensors. Performance assessment against a control denoising method of signal averaging (SA) was implemented in a pilot study with 34 clinical cases. EEMD was found to be a reliable, low latency, data-driven denoising technique with respect to the control SA method, achieving signal-to-noise ratio (SNR) enhancement to a standard closer to the SA control method, particularly on the upper arm-ECG bipolar leads. Furthermore, the SNR performance of the EEMD was improved when assisted with an FFT (fast Fourier transform ) thresholding algorithm (EEMD-fft).

Wearable Technology: Signal Recovery of Electrocardiogram from Short Spaced Leads in the Far-field Using Discrete Wavelet Transform Based Techniques

“…Signal noise appears to be more evident when the dry electrodes are used. This is likely due to the interaction between the subjects' skin and the electrode, which in turn creates a rubbing effect [2]. Lead 2, a dry electrode located on the wrist, performed with a median sensitivity of only 0.292 and PPV of 0.191 as presented in Table 2 As for Lead 6, a conductive gel electrode that is also located on the wrist, the median sensitivity achieved was sufficiently larger than that of Lead 2 at 0.411.…”

“…Furthermore, a second order high pass Butterworth filter at 0.5 Hz was used to limit noise due to respiratory artefact. Also, a second order low pass Butterworth filter at 40 Hz was used to limit the bandwidth of the signal and attenuate out band noise and the power-line interference [2].…”

Arm-ECG Wireless Sensor System for Wearable Long-Term Surveillance of Heart Arrhythmias

“…Nevertheless, effective denoising techniques for arm-ECG are currently available for the treatment of far-field arm-ECG signals. In previous studies [4], bipolar lead electrodes have been positioned (transversally and axially oriented) on different anatomical locations along the left upper-arm. The study has suggested a transversally-oriented bipolar lead on the upper arm (see Lead-1 definition in Figure 1) as one of the most suitable localizations for ECG signal recovery, and that other locations (Lead-4 and Lead-6) can also provide meaningful ECG information.…”

“…In such cases, implantable loop recorders (ILRs) are currently becoming more common and are considered as an important tool by clinicians; however, their use requires costly surgical procedures and carries infection risks [3]. Holter monitors offer high-quality ECG signals for medical diagnosis, but they are typically limited to 24-48 h of continuous use since they require wires that interfere with user's daily activities and skin-adhesive-based electrodes, which may produce patient discomfort after a few days [4] and the adhesive regularly degrades causing electrodes to detach as a result of sweating. Cost-effective, non-invasive, long-term ECG monitoring alternatives for early detection of arrhythmias can have a positive impact on the effectiveness of heart disease treatment, therefore reducing mortality and improving patient's prognosis, particularly in an ageing population [5].…”

“…Their results suggested different locations for accurate ECG signal reconstruction using far-field potentials, especially across the upper left arm. A posterior analysis using advanced denoising techniques was applied to 34 clinical cases showing three primary locations for this purpose [4]. More recently, Vizcaya et al [15] used an arm-ECG database gathered from 153 subjects to develop a method based on artificial intelligence for estimation of standard ECG Lead I using a single bipolar upper-arm ECG signal.…”