I had it for a long time before I had anything done about it - my GP was rubbish, saying it was nothing, but to take it easy if it happened again. Got progressively worse - happening more often, and episodes lasting longer. Got to the point where it was happening consistently 2 or 3 times a week, and lasting anything from 20 mins to 20 hours !
Eventually got referred and monitored a couple of times (unsuccessfully - both times the 'wrong' 24hrs), before presenting at A&E during a particularly bad episode. Had tests and diagnosed by specialist.
GP was rubbish again - prescribed beta-blockers: all they did was slow my resting HR, and slowed by 'fibrilating' HR. It was still irregular, but slower.
Finally went back to specialist, and prescribed Flecainide Acetate (initially 2x50mg, now 2x100mg). Although not completely under control, episodes are less frequent, don't last as long, and aren't as 'violent' when they do occur.
Hasn't had too much effect on training, but I'm aware that the training may trigger an episode, although usually a few hours later. After-effects of episode usually worse than the episode itself - if I've had an episode which has lasts a couple of hours, I feel fatigued afterwards - as though I'd done vigourous exercise for that time. That usually means I'm too tired to do a proper training session, so training is often delayed for a day, or reduced in intensity
Hope this helps. But I'd still suggest seeing your GP in case your's is something different