I was getting atrial fibrillation attacks for 7 or 8 years, mostly in the mornings in winter. I could only sit quietly until it went away, dreadful feeling.
Taking a quarter tsp magnesium chloride everyday cured me very quickly, I don't need to take it any more now that I'm retired and not as active and my reserves are presumably back to normal.
I believe I developed atrial fibrillation because of heavy sweating due to physical outdoor work depleting my reserves of magnesium. All the doctors could prescribe were beta blockers which I soon stopped taking, but it was years before I discovered three people on one website, who had cured themselves of this awful affliction. Very much hope this helps others.