ECG Artifact

Electrode Misplacement


LA and RA electrodes are not interchangeable. Switching these leads will, if not corrected, produce the following deviations from the norm:

  • Abnormal Inversion
    • I
      • A finding of Dextrocardia, but abnormal with proper R wave progression in Precordial leads
  • Abnormal “normal”
    • aVR
  • RAD

Reversing the leg electrodes, whilst not good practice, doesn’t actually produce distinguishable changes on the recorded trace itself; the right leg electrode serves as grounding, and combined with the distance of these from the heart itself, the potentials are essentially the same.

AC Interference


AC current gives a thick line on the recorded trace, as shown. This may be a result of nearby equipment, or the bed/couch itself. To remove it, various filters can be applied to the recording, depending on the monitor being used, but this will also remove some of the desired signal for recording.

The best option is to turn off the bed/couch at the wall, and ensure the same of all non-essential equipment in the vicinity. If the problem persists, record the best possible trace and print one filtered and one without, documenting the process on each.

Baseline Wander


Wander can be the result of a number of things:

  • Patient movement
  • Unclean leads
  • Poor skin preperation

Muscle Tremor


If your patient is not adequately rested and relaxed prior to and during the recording, the biopotentials emanating from the patient’s muscles will be picked up and displayed by the monitor. Poor skin preparation may also account.


Topol, E., Califf, R., Prystowsky, E., Thomas, J., Thompson., (2007) Textbook of Cardiovascular Medicine. 3rd Ed. Philedelphia: Lippincott Williams and Wilkins