title: Quantification of the first-order high-pass filter's influence on the automatic measurements of the electrocardiogram.
abstract: OBJECTIVE
  The first-order high-pass filter (AC coupling) has previously been shown to affect the ECG for higher cut-off frequencies. We seek to find a systematic deviation in computer measurements of the electrocardiogram when the AC coupling with a 0.05 Hz first-order high-pass filter is used.
  
  
  METHODS
  The standard 12-lead electrocardiogram from 1248 patients and the automated measurements of their DC and AC coupled version were used. We expect a large unipolar QRS-complex to produce a deviation in the opposite direction in the ST-segment.
  
  
  RESULTS
  We found a strong correlation between the QRS integral and the offset throughout the ST-segment. The coefficient for J amplitude deviation was found to be -0.277 µV/(µV⋅s).
  
  
  CONCLUSIONS
  Potential dangerous alterations to the diagnostically important ST-segment were found. Medical professionals and software developers for electrocardiogram interpretation programs should be aware of such high-pass filter effects since they could be misinterpreted as pathophysiology or some pathophysiology could be masked by these effects.
authors.affiliation: SCHILLER AG, Altgasse 68, 6341 Baar, Switzerland.
authors.forename: Jonas
authors.initials: J
authors.lastname: Isaksen
authors.affiliation: SCHILLER AG, Altgasse 68, 6341 Baar, Switzerland.
authors.forename: Remo
authors.initials: R
authors.lastname: Leber
authors.affiliation: SCHILLER AG, Altgasse 68, 6341 Baar, Switzerland.
authors.forename: Ramun
authors.initials: R
authors.lastname: Schmid
authors.affiliation: SCHILLER AG, Altgasse 68, 6341 Baar, Switzerland.
authors.forename: Hans-Jakob
authors.initials: HJ
authors.lastname: Schmid
authors.affiliation: SCHILLER AG, Altgasse 68, 6341 Baar, Switzerland.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Generali
authors.affiliation: SCHILLER AG, Altgasse 68, 6341 Baar, Switzerland. Electronic address: roger.abaecherli@usb.ch.
authors.forename: Roger
authors.initials: R
authors.lastname: Abächerli
mesh_terms: D001331:Automation; D004562:Electrocardiography / Q000379:methods*; D006801:Humans
keywords: AC coupling; Automatic measurements; ECG measurements; Electrocardiography; High-pass filter; ST segment