Millions of Americans watched as Buffalo Bills player Damar Hamlin suffered cardiac arrest after a hit on Monday Night Football. He reportedly received CPR on the field and was taken to a Cincinnati hospital after his heartbeat was restored.
What is cardiac arrest?
According to the National Institutes of Health, cardiac arrest occurs when the heart suddenly and unexpectedly stops pumping, preventing blood from flowing to the brain and other vital organs.
Signs of someone experiencing cardiac arrest include collapsing suddenly, having no pulse, non-responsiveness and not breathing.
"Nine out of 10 people who have a cardiac arrest outside of a hospital die — often within minutes," the NIH states on its website.
What causes cardiac arrest?
The NIH explains that the main cause of cardiac arrest is arrhythmias.
However, Hamlin's case may be different since he collapsed immediately after a hit on the field. One potential cause of his cardiac arrest could be commotio cordis, according to the American Heart Association. It's described as a rare phenomenon.
"The blow to the chest at precisely the wrong time in the cardiac cycle causes an electrical abnormality in the heart resulting in an irregular heart rhythm that cannot pump blood to the body," the American Heart Association states.
The organization says doctors will also attempt to determine whether Hamlin has hypertrophic cardiomyopathy, a thickened heart muscle. The Centers for Disease Control says the condition can lead to sudden death, especially in children, young adults, and competitive athletes. They are often unaware they have the condition.
How to respond when someone suffers cardiac arrest
Administering CPR and using an automated external defibrillator (AED) could be key to saving a person's life.