I'm not a competitive endurance athlete, but have swam, biked, other sports for ave 60min+ 2-3x per week on ave for since before age 10 (now 69) and have Atr flutter (prob since age 50/55 but not taken seriously by clinicians as asymptomatic and not easy to pick up w/out full multi-lead ecg - but I felt the slow and irreg pulse when fully relaxed (now always irreg)).
Still asymptmatic except for more awareness and that my max heart rate is down (resting irreg45, was reg55; max 135, was 190) - I train happily and quite fast and hard with others much younger.
Am on anti-fibrin thinner - apixaban and EP/cardiol may be considering ablation for me - but may have had this arrhythmia too long for success?
Thinking about exercise - I am considering more fast sprints with longer recovery might be better than endurance also maybe 4x 40mins per week total rather than 3x 60mins - I'm fairly sure there's little evidence out there. Whatever, like many others I wouldn't find it easy to just stop.
Anyway, have heard plenty of stories and very glad I don't have bad symptoms - my thoughts with those who do.