TCB, I'm sorry to hear about your potential afib incident. I was having a lot of trouble last year with a racing heart and was diagnosed as pre-afib. I know of folks who are able to keep their afib under control with medication. I don't take drugs for mine; for me, magnesium and potassium keep my heart rate where it should be.
I purchased an Omron blood pressure monitor, wrist-style, which is easy to use and very convenient (about $35 on Amazon). It doesn't actually detect the afib (an EKG does that), but the cardiologists don't seem concerned. I like to know that both my blood pressure and heart rate are in the normal range.
When I asked the head of cardiology what to do when these incidents occur, he told me to drink a glass of water and eat some high-potassium foods. I agree that both help. As my incidents usually occur in the middle of the night, I keep a glass of water and some potassium capsules next to my bed, along with magnesium capsules. Magnesium quiets my heart within minutes.
Vibes you have no more trouble with this!