Can't read the actual study because it's behind a medical journal paywall. It looks like they speculate that improved CPR training and AED use has caused this.

Can't read the actual study because it's behind a medical journal paywall. It looks like they speculate that improved CPR training and AED use has caused this. My speculation would be that these mega running nerds all wear watches that track their heart rate 24/7 now. I suspect if something is wrong then you get an earlier detection rather than only discovering it on a race day.