I can't believe I am saying this but...

[That Guy]

i had an irregular heartbeat (Atrial tachnycardia) and it had absolutely no effect on anything i did (except without an ablation your heart wears out earlier from all the extra beats, like at 70 years old instead of 80). Some people pass out when they try to run or do any high bpm activity (which would require an ablation to fix) and others have the extra beat get effectively cancelled out when the heart rate rises above a certain point, in which case there's no adverse effects on physical activity.

A radio frequency ablation is a minor deal that takes about 6 hours (if they can find the area creating the second beat the first time in) and takes about a couple months till there's absolutely no restrictions on running etc (they cut holes near the groin to stick a long tube up a main artery and into the heart to electrically zap the extra beat out of existance).

This is all relevant if he has what i think he has etc, but that's kinda what it sounds like.