There are lots of us!
Dnvrfox, I have been a "member" of afibbers.org since 2002. My afib was never set off by exercise, but usually came from the restful time after a period of stress. Classic vagal afib. Fortunately, it never lasted more than a relatively few hours (except the first few times when they put me in the hospital).
Since August of 2005, I have been afib free except for 1 short episode in April, 06, that was brought on by stress. If I don't drink caffine, don't get heartburn and stay calm, I'm good. I've never had any afib while riding or exercising.
At 57, I'm not going to be racing. However, I got back into riding in the summer of 2006 because I can't run anymore and I wasn't able to motivate myself to get a good aerobic workout except playing basketball. But I would like to get faster, so I just work at it. I don't think the Rythmol has a very strong beta blocking tendency, if any at all, so maybe I've always had a low Max HR and just didn't know it.
By the way, Dr. Natale is reported by the afibbers.org people to be the absolute best in the world, so you either got really lucky or you were really smart.
John