People are looking for answers after Hamlin's collapse.

The Buffalo Bills said on their website that a young man is in critical condition after a hit. He spent the night in the intensive care unit.

The scene horrified players and onlookers alike: Hamlin got up from a tackle and stepped forward before falling backwards, and he was then down on the field for some 10 minutes as medical staff gave him cardiopulmonary assist.

While Hamlin's team and family have yet to confirm exactly what happened, many of the doctors following his case online have narrowed it down to one possible cause: commotio cordis.

A dangerous, life threatening heart arrhythmia or cardiac arrest can be caused by a blunt blow to the chest.

According to the director of the New England Cardiac Arrhythmia Center, only 20 to 30 cases are reported annually.

It has to be a perfect storm of events where there's an impact to the chest wall overlying the heart with just enough force. Within a critical period, it happens. The heart is vulnerable to this because it takes about 20 to 30 milliseconds for the heart to start beating again.

The first few minutes after such an event are critical to the outcome.

defibrillation can be initiated, but how quickly is the most important issue when it comes to sudden cardiac arrest, sudden arrhythmic arrest.

Hamlin's heartbeat was restored at the scene after responders delivered both of those things.

This medical response and the fact that Hamlin is young and presumably healthy are all aspects that could lead to a full recovery.

There are other things to know about Commotio cordis.

It's seen most commonly in projectile sports

Baseball, hockey, and lacrosse involveblunt projectiles that impact the chest wall, which is what Commotio cordis is.

Football isn't dangerous, but it is associated with head injuries more than heart issues. Monday's incident has raised questions about the length of time it took for the game to be postponed and the league announced Tuesday that the game will not resume this week.

According to a 2010 New England Journal of Medicine article, the National Commotio Cordisregistry reported over 200 cases between 1995 and 2010.

Young people between the ages of 10 and 18 are most affected. According to the New England Journal of Medicine, 98% of known victims in the US are boys or men.

About half of commotio cordis cases have been reported in young athletes competing in amateur organized sports who receive a blow to the chest that is usually delivered by a projectile used to play the game, according to a report.

A quarter of commotio cordis events have been caused by recreational activities at home or on a playground, and the final 25% have been caused by fights and accidents outside.

According to the journal article, Commotio cordis is usually, though not invariably, fatal.

The improvement is attributed to rising public awareness, increased availability of automated external defibrils, and earlier and faster life saving actions by bystanders.

There are strategies to prevent it

The rarity of Commotio cordis is so rare that the NFL is looking at ways to prevent it.

There have been studies looking at protective equipment in youth sports.

The New England Journal of Medicine says that while it's unrealistic to eliminate commotio cordis completely, organized sports hold the most potential to prevent it.

There are a number of preventive measures that can be taken. According to the article, coaches can teach inexperienced batters to turn away from the ball to avoid "errant" pitches, and they can teach lacrosse and hockey players to avoid using their chests to block the ball.

Safety baseballs made entirely of rubber or air-filled balls could be improved. According to the article's authors, chest protectors and vests, at least in the form available at the time, were not necessarily effective and could even provide a false sense of security.

If an athlete collapses on the field, it's important for players and spectators to know how to resuscitate them.

The failure of bystanders to appreciate the life threatening nature of the collapse has been associated with deaths.

The availability and use of automated external defibrillators, which are portable medical devices that can be used after a cardiac event to analyze the heart's rhythm and deliver an electric shock, is one of the key factors.

According to the article's authors, a public health strategy that makes AEDs available at youth sporting events and in recreational settings is likely to result in the survival of more young people in the event of cardiovascular disease.

According to the National Conference of State Legislatures, several states have proposed or adopted laws that require the use of automated external defibrilators at school athletic events.

The state of New York passed a law in 2002 requiring all public schools to have at least one automated external defibrilator. Louis' Law is named after a student who died while playing lacrosse at his first high school game.

The Red Cross has guides to use an aED and perform cardiopulmonary resuscitation.