I had to adjust the value for it to alert since my normal resting BP is higher than most people (90s-100s) and even being excited or engaged in a great action movie would trigger it. I set mine to 130 bpm since 120 is about my max resting BPM.
Never got an a-fib alert. Never knew that existed (ECG has been no-go since I got my Series 5--always inconclusive (Galaxy Watch shows sinus rhythm) so I gave up on it)
A few ideas:
Your watch might need replaced. With my old Series 5, I always got smooth sinus rhythm readings, every time.
The ECG on my Series 6, after a few months of owning it, stopped working. It would constantly go back to 30 seconds after a few seconds of reading, and was often inconclusive.
My Series 7? Flawless, never a bad reading.
Stuff like wearing your watch too high on your wrist, too loose or too tight, the back of the watch being dirty…it’s likely that none of these are the problem here if you’re
always getting inconclusive readings.
I’d take it into the Apple Store and show them. You might get a new (refurb) Series 5 (or maybe better) out of it.
Then you’ll have an Apple Watch with a functional ECG
and a brand new battery. That’s a win-win.