What are high pass filter and low pass filter in ECG settings?

What are high pass filter and low pass filter in ECG settings?

High pass filters allow only frequencies above the set limit to pass through and hence eliminate components below a particular frequency. For surface ECG, the high pass filter is usually set at 0.05 Hertz in order to preserve the T wave and eliminate baseline drift, typically due to respiration.

Low pass filters on the other hand allow only frequencies below the set limit to pass through and hence eliminate components above a particular frequency. Often it is kept at 40 Hertz to reduce high frequency artifacts due to pick of muscle potential or electromyogram. As a tradeoff, it will often remove pacing artifacts which are high frequency signals as well.