The short form is that EEG is brain and ECG is heart, and you only want to see brain waves, not heart waves - it's pure interference, that changes the shape of

The short form is that EEG is brain and ECG is heart, and you only want to see brain waves, not heart waves - it's pure interference, that changes the shape of the wave. It's simply 'not the thing we're looking for'. Most clinical EEGs are related to epilepsy or similar, which usually has a particular pattern with spikes in it, but sometimes that pattern is subtle in the EEG. The spiky nature of ECG 'bleeding through' can make it a bit harder to determine the true EEG spikes from the artifact ECG patterns. Usually you will record a single-lead ECG along with the EEG, so you can see where the ECG spikes occurred and account for them in diagnosing the EEG. This link has some clear spike-and-wave epileptic waveforms in it, but it's not always so clear-cut: https://en.wikipedia.org/wiki/Spike-and-wave https://en.wikipedia.org/wiki/Spike-and-wave Finally, there's not a lot of overlap between neurological and cardiac patients - there's rarely any need for an EEG tech to do a full ECG (we never did, and we did approx 3200 patients/year), and full ECGs are pretty commonly done in most other places in a hospital anyway.