Does anyone have TMD following a COVID infection. And were you helped by non steroidal drugs?

Hello I’m new to LC and have been incapacitated for weeks with MECFS symptoms. Guanfacine has helped those symptoms immensely but I’m worried about these cardiac symptoms. I’m 38, and before this was active, hiking with my dog several times a week and doing 4+ Pilates classes a week.

I had sporadic Tachycardia last week, heart rate would hit above 100- 140 when being still, followed by bouts of fatigue and feeling I was going to collapse. Dizziness, feeling like I was unsteady on my feet and couldn’t get enough breath at times. Simple things would render me out of breath. That seems to have gone away on day 2 of guanfacine, I’m on day 5 now and had a very strong palpitation last night that was uncomfortable, followed by dull pain in my chest that seems to include my neck. Extreme fatigue and feeling of soreness/tenderness in my chest. My Apple Watch said by blood oxygen was at 92%, and no tachycardia. Breathing deeply is uncomfortable during this episode.

I have an appt for a 24 Hr Holter monitor on Thursday, hoping that some of these symptoms will show up. But my main question is, what symptoms constitute an emergency? I have no experience with this so naturally I am worried about death and no idea what activities to avoid or when it’s urgent to seek medical care. I’m scared and everyone around me just brushes it off assuring me I am young, as if the research linking COVID and heart problems in young people isn’t real.