I had a-fib and a successful ablation in Sept 2013. It was very obvious for me. One week I was in the break all day at a hilly road race, and a few weeks later I could not get up a flight of stairs without feeling very week. I also got dropped before the group ride started. I was "lucky" because when I went to the doctor I was stuck in a-fib so he could diagnose it right there. Like you I thought my HRM was on the fritz.

I read the Velonews article and while parts are misleading, the gist is correct. Basically a lot is still unknown but there is a link between excessive endurance sports and the heart issues he describes. My doctor was a runner and gave me the green light as long as I take a day off every week, a week or two off every 6 months, don't chug coffee after sleeping like poo and go hammer, all stuff you should be doing anyway, and of course I was not. I made a full comeback, 100%, but it took a while and hard work. KQ'd 6 months after ablation.

What you describe sounds like you should find the best heart doctor in your area who also is an athlete, and go see him, and do exactly what he says even if you do not like it. I love ST, but don't listen to anybody on here when it comes to your heart.

I should add I have a-fib on both sides of my family.