Removal of ECG artifacts from EMG signals with different artifact magnitudes by template subtraction

Lorenz Kahl,Ulrich G Hofmann

doi:10.1515/cdbme-2019-0090

Lorenz Kahl, Ulrich G Hofmann

Open Access

https://doi.org/10.1515/cdbme-2019-0090

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Abstract

AbstractThis work investigates the performance of eventsynchronous noise cancelling algorithms to separate ECG artifacts from thoracic EMG recordings. In focus are the precise detection of heart beats, the exact time alignment of the QRS segments and the construction of a template QRS signal. Among the utilized methods is a modified structural intensity (SI) approach based on the observation of extrema in low pass filtered versions of the second derivative as a detector. An adoption of this approach is also used to obtain the exact time alignment of QRS segments. Artificial test signals are constructed based on addition of ECG and sEMG with different magnitudes. We show that approaches based on the observation of extrema in different scales yield superior results.

Highlights

Analysis of surface electromyography can play a helpful role in gaining information about the state of muscles in a noninvasive way
The results of a detector based on flank threshold intersection showed a poorer performance especially at larger EMG magnitudes
The results clarify that it is reasonable to separate the tasks of detecting the QRS segments and finding their exact time for event synchronous ECG noise cancelling

Summary

Introduction

Analysis of surface electromyography (sEMG) can play a helpful role in gaining information about the state of muscles in a noninvasive way. Surface EMG recordings from muscles close to the heart are often contaminated by cardiogenic disturbances. Methods based on adaptive noise cancelling were proposed to isolate the EMG and the ECG part of the signal. Strobach et al [8] proposed a method that utilizes the repetitive nature of the cardiogenic artifacts. A template QRS segment is estimated by event-synchronous averaging of the contaminated signal. The cardiogenic artifacts are canceled by time-synchronously subtracting this template from the contaminated signal. The key components of such an eventsynchronous interference canceller are (1) the QRS detector, (2) the determination of the exact time alignment and (3) the construction of the template.

Methods

Results

Conclusion