Last year, when I was flaring really badly, about once a week, I would get what I assumed were palpitations. For about 20 seconds, I would feel really dizzy and my heartbeat was irregular (a bunch of really quick beats and then no beats for a few seconds). I also hadn't really worked out in about 5 years at the time.
The past six months, I've been lifting and running about 3 miles/day. Since I've gotten into better shape, the heart thing hasn't happened to me at all. My resting heart rate is also 10-15 beats/minute lower than it used to be.
I never spoke to my dr about it, so I'm not really sure what it was or what was causing it, but regular exercise has definitely helped, maybe even eliminated it.
-Greg