This sounds quite familiar to me. Three years ago I was diagnosed with paroxysmal Afib and put on meds. My triggers were vigorous physical activity, dehydration and poor sleep (among others). At 71 I returned to Nepal for a challenging remote trek at altitude. I trained hard on local ski hills and was in excellent shape but was unsure how I’d do at higher altitudes (4,800M). Our first day started fine - hiked 4 hrs in the morning and I felt great. But an hour after stopping for lunch I hit the wall energy-wise, which fit my previous pattern where afib would usually kick in an hour after exercise. Our route that day had a glitch and turned into a 9 hour slog in very hot humid temperatures, at very low altitude. My heart rate averaged 121 over 7 hours and hit 186 - very tough day! I recovered the next day and as we trekked higher over the next few days (more normal days) I was fine until we reached 3,400M and I could not go on as my afib started right away when I tried to move on. I had to abandon the trek unfortunately but was fine thereafter. It was extremely disappointing, especially as I had trekked Nepal 3 previous times and handled over 5,000M without a problem. Five months ago I had an ablation and have not had an Afib episode since. My energy levels are great and I can exercise vigorously without triggering an episode. I even started playing hockey. Huge relief. I am reluctant to try another trek at altitude but have not ruled it out completely. BTW - I used a kardamobile device several times a day so I could record readings and present data to my cardiologist rather than trying to convey my experiences in my usual 5 minute verbal conversation with him. Seeing the data finally convinced him to refer me for an ablation which has been a life-changing event thus far. I’ve had a knee and hip replacement and the ablation is on a par with those as far as returning to normal life is like. I know what it is like to fear having to stop doing what you love due to afib - it can be devastating. So my advice is to discuss the possibility of an ablation with your doctor - I wish you all the best.