I'm looking into buying an Apple Watch, as I'm currently going through several health issues, including some that are heart related. I have some different heart arrhythmias, including a pretty decent sinus arrhythmia (at it's worst, my heart beat can increase by 30-40 beats when I inhale).

I was playing with my friend's watch the other day, and it interpreted the EKG as showing afib. Yesterday I had to call an ambulance (another heart related issue) and I mentioned that to them, they said there was no sign of afib at that moment, but their experience was that sometimes if a sinus arrhythmia is particularly bad, that it will read that as afib. He was pretty sure that you could change the settings somehow, so that the watch knew not to be so "sensitive" when reading my results.

There was no actual sign of afib on the readings my friend's watch either. I asked about it here.

Is it possible to "personalise" the settings like that on an Apple Watch?