I, m 67, had 2 cardio versions and 2 catheter heart ablations. Heart been back in sinus rhythm since last November. On usual meds incase it reverts back.
I, m doing roughly 70 miles per week off road around Peak District, with about 5000 ft climbing,on Giant Fathom E2. Only use highest setting. My consultant insisted I keep cycling but not to push it too hard and stop if chest has any signs of pain. Have got Garmin Fenix watch which records all GPS data and all heart stats.(set it to vibrate if I exceed 160 bpm). It also gives a score for training effect (aerobic and anaerobic) which is a perfect way to make sure I don't over do things.
With bike, watch, fair bit of relatively easy work and lots of fun I, ve got my Vo2 upto 40 and training age down to 47.
Check with your consultant to give his thoughts but I suspect emtb has been a life saver for me. Bought my first around 5 years ago when AF was at its worst.
Good luck.