GP could have been having a non STEMI heart attack.

I was, actually, but I don’t know how that’s connected? This was something like a ten minute spike in the middle of the night, a couple of times.

The sympathetic nervous system activates, increasing heart rate and the body is trying to compensate for the compromised heart muscle. Then, there is the possible adrenaline surge because you are actually in pain. If the NSTEMI causes left ventricular dysfunction, the heart compensates with a faster rate to maintain blood flow.

I went through this with a relative just two weeks ago and learned this from the cardiologists

I was lying down at rest.