I had been previously dx with POTS and POHS (Postural Orthostatic Tachycardia and Hypotension).
Random heart rate spikes as high as 200 beats per minute accompanied with shortness of breath, nausea and flushing, All with little to no exertion. These episodes were followed by Post Exertional Malaise and major fatigue. For these symptoms I was prescribed Metoprolol. Typically a blood pressure medication, but can also affect heart rate. Almost immediately my heart rate and shortness of breath calmed, and nausea ceased. Prior average HR of 80’s-90’sbpm and spikes from 135-175bpm with multiple heart rate alerts daily for extended periods over 100 (Apple Watch monitor) were reduced to average HR of 60’s-70’sbpm with no spikes nor alerts. Out of everything, this was my “miracle drug”. I’m also enjoying being able to use my Apple Watch for something other than a constant heart monitor…

For flushing, I was prescribed a very low dose of Estradiol hormone replacement. My frequency and intensity of body flushes have improved to manageable. Even after 10 years, I still have the occasional menopausal hot flash, so there might be a little blending of symptoms.

Other symptoms have been heart palpitations; chest pain/pressure; ongoing shortness of breath, depression, anxiety. For depression-Rx Wellbutin (Bupropion). For anxiety-Rx Cymbalta (Duloxetine). My doc chose Cymbalta because it is also known to help [nerve] pain. I have been taking it for several weeks with one increase in dose. It appeared to be helping both anxiety and chest pain, but the chest pain seems to come back after a couple weeks.

If any of these results would be similar to your situation, I would bring the drugs up to your doc to review and/or prescribe.

Let me know if you have any other questions.
My best to you.