@dfelix, as you get more responses and do internet searches you will find there are many A-fib triggers but what causes the condition in the first place is still somewhat a mystery. In my case it seems to be caused or triggered by an excess of thyroid hormone. I have been hypothyroid (underactive thyroid, not producing enough hormone) to I have taken either Synthroid or a natural desiccated thyroid extract. If one's TSH gets too low, A-fib can result. Although this may not be your problem, it never hurts to have your PCP do a thyroid workup and at least eliminate that as a potential problem. God bless.