@Needsomegoodies
Sorry to hear you're suffering with your heart. I'm experiencing the same problems you've mentioned.
Mine is all over the place. It rests fine but will quickly shoot from 50 to 100 when I stand up or sometimes for no apparent reason.
The pounding gets amazingly strong at times. It pounds for most of the day but ebbs and flows in intensity. Like you, it keeps me awake sometimes because it jolts my whole body.
I'm also getting the skipping beat / big thud very occasionally.
If I rest for a day or 2 the pounding is noticeably better the next day. It's still there but it's very low level. If I increase exertion the pounding returns, so it's clearly related to exertion.
I've had 2 ECGs both of which have been clear. I'm having a heart echocardiogram in the next week or so, which I learned yesterday was to look at heart valve function.
I don't think its a mechanical problem though. My fatigue, heart are terrible in the morning but improve over the course of the day.
In the morning I awake feeling SOB, weak, dizzy, shaky and disorientated but by early evening I feel like a different person -- physically and mentally. My heart beat is consistent, it doesn't race on standing and the pounding is muted. I have energy and feel more like my old self again.
Something happens to me in the night. I sleep fine from 9 until 1am and then It's as if my body reboots when I awake from deep sleep 1. I awake from that at 1am with a racing, pounding heart and then drift in and out of physically and mentally painful sleep until 6am. It's like groundhog day.
The heart issues outlined above fit in with the symptoms of PoTS, which can occur as a result of CFS -- or hopefully temporary post viral syndrome.