The triboelectric effect is the build-up of static charge due to the rubbing of two different materials against each other (for example, an ungrounded conductor and the insulator of the ECG cable).

Effect on ECG Waveform
Introduces a slowly varying change in the baseline voltage (baseline drift) of the ECG signal

Effect on MR Data Acquisition
Baseline drift results in either positive or negative change of the mean ECG signal. If a threshold value is used to detect the trigger point, noise spikes can be detected if the drift is positive, or the R wave can be missed if the drift is negative. Miscalculation of the R-R interval resulting from false ECG triggers results in degraded image quality because data are collected at a different phase of the cardiac cycle than expected.