A solution to difficult power frequency interference on ECG recordings.

Abstract

Line, or 50 Hz, interference is a common feature of ECG recordings where either the instrument performance is unsatisfactory or the tissue electrode preparation is inadequate. With the superior performance of modern ECG machines, the electrode preparation required is minimal. Any interference present on the recording can usually be eliminated by a reapplication of the electrodes. Where it is persistent, this may be due to a magnetic field interacting with the loop formed by the electrode leads and the subject. Reducing the loop area by repositioning the electrode leads will usually produce a clear recording. A particular area in an ECG department, designated for routine ECG recordings, produced tracings contaminated with over 0.4 mV peak to peak of interference despite all efforts to eliminate it. After investigation, a novel solution was developed which actively reduces the environmental power line magnetic field. Three adjacent examination couches have been treated and are now satisfactory for routine ECG determinations with no noticeable interference.