The NFL is investigating every possible cause behind the cardiac arrest of Buffalo Bills safety Damar Hamlin, which resulted in his collapse mid-game against the Cincinnati Bengals, according to the NFL’s chief medical officer Dr. Allen Sills. 

“I know there's been a lot of theories and a lot of discussion about commotio cordis, and that certainly is possible,” Sills said Wednesday on a press call.

Commotio cordis happens when severe trauma to the chest disrupts the heart’s electrical charge, causing dangerous fibrillations. 

Sills said it is a diagnosis of exclusion, meaning it might be the diagnosis if doctors don’t find any other causes.

“You have to have the right type of blow hitting at the right spot on the chest with the right amount of force at just the right time in that cardiac cycle. So a lot of things have to line up for that to happen,” Sills said.

Doctors will look for any potential congenital or other abnormalities with Hamlin’s heart, he said. Every player gets a physical before each season, and doctors take a detailed medical history, which includes American Heart Association screening guidelines related to potential cardiac issues.

Sills said any time a player is evacuated from the field, the NFL and its medical experts do a detailed review of what happened. They will also look specifically at the role of protective equipment. 

“I think that’s something that certainly we want to look at,” he said. “We do know that padding over the sternum can be protective to blows in situations where commotio cordis is a consideration, so that is something that certainly will be discussed.”

Currently, players’ shoulder pads typically fit in an area that covers the sternum, he said.

Sills said that in some cases, the medical team will not be able to determine what caused the problem.

Regardless of the cause, what helped in this situation was that the NFL had the right people and equipment in place to provide “an extremely rapid response,” he said.”