The machines are generally
up.
If I performed an ecg on all the patients in the waiting room, then about 75% would be shown to have an abnormality. If I looked deep enough (incorporating some blood tests etc), then I reckon I could find something "wrong" with most of 'em.
You need a human to separate the wheat from the chaff.
Your history (the story you tell of your symptoms) is uneventful.
I'm not clear why the authorities continue to perform resting ecg's. There is no correlation between performing ecg's and planes falling out of the sky.