Random rapid heart rate tapering off of prednisone?

You may just need magnesium supplements. I had several episodes of rapid and fluxuating heart, and did an Afib test on my Apple watch, which showed I did have Afib. I started taking Magnesium and it hasn't happened again. I take Magnesium Theronate in the morning and Magnesium Gycinate in the evenings ever day. Most people are deficient in magnesium.

I’m experiencing the same as you are while tapering. Started at 40mg and reducing every week by 5mg. Right now, I’ve reduced from 40, 35, 30, 25, 20, 15, and 10; so, 7 weeks in. Next week will my last week with 5 mg. Are you any better? My resting heart rate used to be 65 and getting bouts over 100bpm. I’m concerned. Thank you.

All I know is prednisone tapering messes with cortisol and our bodies are trying to adjust to the changes in dosage. While doing so it makes our bodily functions confused and they don’t operate normally.
I have been on a taper and have noticed an irregular heartbeat notification more consistently on my blood pressure monitor lately.
I am scheduled for a heart monitor next week so maybe it will determine if there’s an issue.