Digital DC-Reconstruction of AC-Coupled Electrophysiological Signals with a Single Inverting Filter

PLoS One. 2016 Mar 3;11(3):e0150207. doi: 10.1371/journal.pone.0150207. eCollection 2016.

Abstract

Since the introduction of digital electrocardiographs, high-pass filters have been necessary for successful analog-to-digital conversion with a reasonable amplitude resolution. On the other hand, such high-pass filters may distort the diagnostically significant ST-segment of the ECG, which can result in a misleading diagnosis. We present an inverting filter that successfully undoes the effects of a 0.05 Hz single pole high-pass filter. The inverting filter has been tested on more than 1600 clinical ECGs with one-minute durations and produces a negligible mean RMS-error of 3.1*10(-8) LSB. Alternative, less strong inverting filters have also been tested, as have different applications of the filters with respect to rounding of the signals after filtering. A design scheme for the alternative inverting filters has been suggested, based on the maximum strength of the filter. With the use of the suggested filters, it is possible to recover the original DC-coupled ECGs from AC-coupled ECGs, at least when a 0.05 Hz first order digital single pole high-pass filter is used for the AC-coupling.

Trial registration: ClinicalTrials.gov NCT00470587.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Clinical Trials as Topic
  • Electricity*
  • Electrocardiography / instrumentation*
  • Electrocardiography / methods
  • Electrophysiology / instrumentation*
  • Electrophysiology / methods
  • Equipment Design
  • Heart Diseases / diagnosis
  • Heart Diseases / pathology
  • Humans
  • Reproducibility of Results
  • Signal Processing, Computer-Assisted*

Associated data

  • ClinicalTrials.gov/NCT00470587

Grants and funding

SCHILLER AG, Baar, Switzerland, founded the study with employment payment (all authors). The founder did not play a role in the study design or in the data collection. The data was collected within the clinical studies SwissAF and APACE and anonymized before being used for this study according to national laws. The founder helped with the analysis of the resulting data and made the decision to publish, as well as helping write and countercheck the manuscript.