Fast and reliable QRS alignment technique for high-frequency analysis of signal-averaged ECG

Abstract

The process of QRS alignment as required in signal-averaged ECG can impose serious limitations on the spectral range of the signal output. This effect depends basically on the particular alignment technique being used and on the level and type of noise present in the recorded ECG. In clinical studies where a wide-band (1000 Hz) ECG averager is required, the conventional QRS alignment technique, based on maximum coherence matching (MCM) with a template beat, may not perform consistently well. An alternative QRS alignment technique based on the accurate detection of a single fiducial point (SFP) in the bandpass filtered (3-30 Hz) QRS complex was developed. Using computer simulation methods, a comparative assessment of the frequency bandwidths (3 dB points) offered by both MCM and SFP techniques as a function of noise level (15-100 muRMS) and type (EMG and 50 Hz interference), was carried out. The results of the comparative assessment indicated a better performance by the SFP technique in all cases of noise. Hence, the SFP technique would perform more reliably for high-frequency analysis of a noisy ECG, especially when 50 Hz interference is high. Furthermore, SFP is considerably faster than MCM (about four times) when implemented digitally, and its analogue realisation is feasible. The SFP technique is suitable for late-potential analysis in the signal-averaged ECG.

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

“…In this study, the particular SA-ECG denoising technique was not a data-driven type, unlike the current EMD (empirical mode decomposition)-based method. The implemented SA technique uses Lead I or any of the other simultaneously recorded standard limb leads: Lead II, Lead III and the precordial lead V 1 , for extracting the accurate, time-deterministic point associated with the heart ventricular depolarization event during normal sinus rhythm, by means of the single fiducial point (SFP) heart beat alignment technique on the ECG Lead I signal [15], as explained in the following section.…”

Arm-ECG Bipolar Leads Signal Recovery Methods for Wearable Long-term Heart Rate and Rhythm Monitoring

“…Signal measured from the isovoltaic area extending between the S wave terminus and the initial inflection point of the T wave is considered to be noise, as there is a pause in cardiac electrical output in this area. The QRS complex is the highest amplitude area of the ECG and is measured as the signal component [7]. Figure 6 shows the measurement areas on an averaged ECG trace.…”

Ensemble empirical mode decomposition based ECG noise filtering method

“…(5) If d(t) becomes a zero-mean process, then the iteration stops and d(t) is an IMF1, named c 1 (t); otherwise, go to step (1) and replace x(t) with d(t). (6) Calculate the residue signal r(t)=x(t)íc 1 (t).…”

“…During an ECG measurement various noises, such as muscle noise, baselines wander and power-line interferences are recorded in the ECG signals and interfere with the ECG-information identification. Therefore, ECG noise reduction is an important issue and has been studied for many years [1][2]. Numerous signal-processing methods have been used in the studies of ECG noise reduction.…”