The AFib forum is with Health Unlocked Elwood;-
https://about.healthunlocked.com/
You need to sign up as a member and should be able to do so from that link - they have forums for all sorts of things, but it's easy to get to the one you want and you can set it up to get e-mail notifications every day telling you what's been posted on there.
I had to go for an INR yesterday. I've been on Warfarin for eleven years now and in all of that time, I've had very few problems with keeping in the target range, but yesterday my blood shot out from the pin prick to my finger and it was obvious my INR was going to be too high - it was 3.8 (my target is between 2 and 3) and the doctor told me she was expecting it to be a lot higher than that given the way my blood came out. I'm at a loss to think why it should be like that when it's usually spot on or close to it because I haven't changed my diet or been eating or drinking things that I shouldn't. I'm beginning to think that I may have taken too much Warfarin on Monday evening because it becomes the sort of thing you do unthinkingly and I may easily have done something like that if I was distracted. Anyway, I've got to go back next Tuesday for another test which is more of a nuisance than anything else - I'm not too concerned because all they'll do is reduce the dosage if it's still high, but it is odd why it was at that level.
Your message makes clear why you got that letter and I wish you and your wife all the best over the coming weeks and, hopefully, not too many months.