I’ve had EMG studies - where they stick needles into your muscles, pass an electric current between them and watch the response. It’s perceived as a twitch. Doing that on my upper arms didn’t bother the sensor at all. An ECG is a detector of output, there is no input so there is no chance of the sensor noticing.
That’s physics, again.
In a similar fashion, an X-ray or CT scan will have no effect, because X-rays just pass straight through you (knocking off a few bits of DNA) but that won’t bother the sensor. MRI scans agitate receptive molecules for imagery, and thus will melt the metal in the sensor (or any rings you are wearing). The last MRI I had just happened to be a couple of days before sensor change, so no great loss chucking into the clinical waste bin.