Any patterns to AFib?

My 32 year old husband has had 2 episodes of AFib in the past couple months.  Newly diagnosed, and all tests came back perfectly normal.  He's on Atenolol, 25mg.  Does this really help prevent an episode?  Should he avoid playing soccer, or anything else, for that matter?  Is AFib completely random in timing and duration?  Is there ANYTHING he can do to avoid future episodes, or will this continually get worse?  Is there anywhere I can look to for answers as to why a perfectly healthy, athletic young man would get this?  Thankyou for your time.

[CCF CARDIO MD - DLB]

Atenolol has a weak effect in preventing afib. It certainly helps keep the rate form going too fast if he pops into afib. Sometimes, young healthy people develop afib for no apparent reason. Fortunately, they tend to do very well with it. He does not need to avoid exercise, but probably ought to avoid alcohol and caffeine.