Not an expert by any means, but it seems that as we age or our hearts don't function electrically quite like they originally did, then things that originally didn't bother us become A-fib triggers. It's one reason that rather than immediately checking in with the cardiologist that I step back and try to think if I've done something different that might be a trigger. I've gotten careless about what I eat later in the evening recently, and my stomach has reminded me that it doesn't care for coffee or at least the acid part. Thankfully when I've had A-fib lately it's been what seems to be called "controlled" - pulse rate doesn't go over 100 when it spikes.
The first time I had A-fib the peak pulse rate was in the 200 range - not a way you want to learn about something new. Even that time, I converted on my own while on the way to the hospital. I didn't wind up being admitted to the hospital after all but wound up on Digoxin for a while. That was the morning the doc said "It's time" for the replacement valve. A couple of shocks I absolutely wasn't ready for that morning. At least a lot of the new heart procedures aren't open heart. The first replacement aortic valve was open heart, a few days in the hospital, and then a period of recovery at home - coughs and sneezes were killers. The newest valve went in via a catheter - so much easier.