title: Digital DC-Reconstruction of AC-Coupled Electrophysiological Signals with a Single Inverting Filter.
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.
authors.affiliation: Signal Processing and Research, Research and Development, Schiller AG, Baar, Switzerland.|Cardiovascular Research Institute, University Hospital Basel, Basel, Switzerland.|Bern University of Applied Sciences, Bern, Switzerland.
authors.forename: Roger
authors.initials: R
authors.lastname: Abächerli
authors.affiliation: Signal Processing and Research, Research and Development, Schiller AG, Baar, Switzerland.|Laboratory of Experimental Cardiology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jonas
authors.initials: J
authors.lastname: Isaksen
authors.affiliation: Signal Processing and Research, Research and Development, Schiller AG, Baar, Switzerland.|Bern University of Applied Sciences, Bern, Switzerland.
authors.forename: Ramun
authors.initials: R
authors.lastname: Schmid
authors.affiliation: Signal Processing and Research, Research and Development, Schiller AG, Baar, Switzerland.
authors.forename: Remo
authors.initials: R
authors.lastname: Leber
authors.affiliation: Signal Processing and Research, Research and Development, Schiller AG, Baar, Switzerland.
authors.forename: Hans-Jakob
authors.initials: HJ
authors.lastname: Schmid
authors.affiliation: Signal Processing and Research, Research and Development, Schiller AG, Baar, Switzerland.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Generali
mesh_terms: D000465:Algorithms; D002986:Clinical Trials as Topic; D004560:Electricity; D004562:Electrocardiography / Q000295:instrumentation* / Q000379:methods; D004594:Electrophysiology / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D006331:Heart Diseases / Q000175:diagnosis / Q000473:pathology; D006801:Humans; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted