Buffalo Bills safety Damar Hamlin remained in critical condition Tuesday night after his heart stopped beating during a game in Cincinnati Monday.
The Bills say Hamlin suffered a cardiac arrest, which is different than a heart attack.
A heart attack is related to circulation — when blood can no longer get to the heart.
Cardiac arrest is an electrical malfunction where the heart suddenly stops beating properly.
One of the theories that is spreading is that Hamlin suffered commotio cordis.
Dr. Charles Henrikson, who specializes in heart rhythm dysfunction at Oregon Health & Science University, says it is “a blunt hit to the chest that, if it’s timed just right, can put you into a bad rhythm.”
It’s also possible Hamlin had a pre-existing condition, but it’s not clear if that was the case.