This is more of a wondering, and chat thing, rather than wanting a diagnosis of a specific issue. Might even count as a woo question…
My son (teenager), has a couple of medical issues, but nothing that impacts his getting up in the morning, eating, sleeping etc etc. He is about to start a research trial for a new medicine, for his long term condition.
Before doing so, they wanted to do a million tests, obviously, including an ecg, so heart/blood vessels tracing to check all is well on that front.
They couldn’t get a trace. At all. They tried -
- 3 different machines,
- 2 completely different sets of stickers
- 2 completely separate lots of leads
- 2 different electricity points - even though the machines was clearly on, and “working”.
They had just done a morning of testing other kids, so they knew that all these machines work, and so do the leads. The leads were going to limbs, not just the chest, so not a specific issue in one point of the body.. and no one seemed concerned, just truly baffled.
DS thought it cool, and keeps telling everyone he’s “heartless”. 
We’re home again now, and they’re going to try again next visit. Weird, but still wondering hours later, what happened?!