Dr. Barry Maron was watching the Monday night game between the Buffalo Bills and Cincinnati Bengals when he saw Damar Hamlin absorb a hit, rise and collapse. Everything about the injury immediately suggested commotio cordis, he said.
"Clinically it seemed classic because there was the chest blow and then for five seconds or so he tolerated the arrhythmia that followed. That's what usually happens," Maron said.
Maron, a cardiologist at Lahey Hospital & Medical Center in Burlington, Massachusetts, is considered one of the world's top researchers on the subject. With the help of Maron and other research, here are some key questions and answers about the injury Hamlin suffered, which appears consistent with commotio cordis, and what it means for his health:
What is commotio cordis?