Table of Contents
ISRN Cardiology
Volume 2012, Article ID 706217, 10 pages
Research Article

High-Bandpass Filters in Electrocardiography: Source of Error in the Interpretation of the ST Segment

1La Fe Research Institute, Avenue Campanar 22, 46009 Valencia, Spain
2Department of Cardiology, La Fe University Hospital, Bulevar Sur S/N, 46026 Valencia, Spain
3Department of Electronic Engineering, Polytechnic University of Valencia, Camino Ver S/N, 46022 Valencia, Spain

Received 22 March 2012; Accepted 29 April 2012

Academic Editors: Y. Khaykin, R. Lazzara, T. Ohe, and J. A. F. Ramires

Copyright © 2012 F. Buendía-Fuentes et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Introduction. Artifactual variations in the ST segment may lead to confusion with acute coronary syndromes. Objective. To evaluate how the technical characteristics of the recording mode may distort the ST segment. Material and Method. We made a series of electrocardiograms using different filter configurations in 45 asymptomatic patients. A spectral analysis of the electrocardiograms was made by discrete Fourier transforms, and an accurate recomposition of the ECG signal was obtained from the addition of successive harmonics. Digital high-pass filters of 0.05 and 0.5 Hz were used, and the resulting shapes were compared with the originals. Results. In 42 patients (93%) clinically significant alterations in ST segment level were detected. These changes were only seen in “real time mode” with high-pass filter of 0.5 Hz. Conclusions. Interpretation of the ST segment in “real time mode” should only be carried out using high-pass filters of 0.05 Hz.