Hamlin was administered CPR on the field, ESPN reported, and he was surrounded by teammates, some of them in tears, after he was hurt while tackling Bengals receiver Tee Higgins.
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Dr. Anthony Cardillo, an ER specialist in Southern California, offered his insight into what he saw examining the hit and how Hamlin reacted to it.
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"What we can tell is the event was most probably secondary to that hit," Cardillo said.
When talking about the injury, Cardillo mentioned the "R-on-T" phenomenon, explaining:
"This is a phenomenon that when the heart is going between its beats, as that heart is depolarizing and then repolarizing, if you have traumatic trauma to the chest, at a very specific moment as that heart is repolarizing itself, you can go into a lethal ventricular arrhythmia, and that's what it looks like happened," Cardillo said.
Dr. Anthony Cardillo's full interview can be viewed in the media player above.
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Hamlin spent five years of college at Pittsburgh - his hometown - and appeared in 48 games for the Panthers over that span. He was a second-team All-ACC performer as a senior, was voted a team captain and was picked to play in the Senior Bowl.
He was drafted in the sixth round by the Bills in 2021, played in 14 games as a rookie and then became a starter this year once Micah Hyde was lost for the season to injury.
By late Monday night, a community toy drive organized by Hamlin had surged to more than $900,000 in donations. His stated goal was $2,500.
The Associated Press contributed to this report.