One freak bolt of lightning within a five millisecond time frame or ...
there could not possibly be any other reason!
Assume Heart rate = 60 bpm
One beat = 1000ms
5/1000 = .005
So, only a 1/2 % of happening with every NFL hit on the right spot on the chest.
Sounds like it could be a fairly likely outcome each NFL season.
A 5 millisecond window implies 1/200 chance of a of the hit coming during that window. I would think there might be more than 200 such hits in a year, or was it and extremely violent hit? How did the doc rule out a preexisting heart condition?