A rare but potentially lethal heart disruption known as commotio cordis may have sent Buffalo Bills defensive back Damar Hamlin into cardiac arrest seconds after a hard tackle during a game Monday night against the Cincinnati Bengals.
Hamlin, 24, collapsed after he collided with a Bengals receiver during a tackle and appeared to take a hit in the head and chest. Hamlin stood up, took a few steps and fell backward.
Medical personnel used CPR and an automated external defibrillator on Hamlin on the field for nearly 10 minutes and restored his heartbeat. He was taken by ambulance to the University of Cincinnati Medical Center, where he was in critical condition. The game was officially postponed.
Though it’s not certain what sent Hamlin into cardiac arrest, commotio cordis is usually sports-related, caused by a blow to the chest wall just outside the heart.
What happens during cardiac arrest?
A 20-millisecond window
The heart’s electrical cycle is key to understanding when commotio cordis could happen:
- After the P wave, in which the muscles of the right atrium contract, forcing blood into the ventricle.
- Before the T wave, in which the heart prepares to pump out blood.
Though devastating, commotio cordis is considered rare because it has a narrow window in the heart’s beating cycle to take effect.
A cardiac cycle lasts about 0.8 seconds, or 800 milliseconds. (A millisecond is one one-thousandth of a second.) Commotio cordis takes place within a 20- to 40-millisecond window of the cardiac cycle.
How common is commotio cordis?
Commotio cordis is usually seen in athletes playing sports using equipment such as:
- Hockey pucks
- Lacrosse balls
These objects can strike players in the chest with enough force to cause an arrhythmia. Commotio cordis most often occurs in baseball; pitchers, catchers and hitters are at highest risk.
Fewer than 30 cases are reported each year, according to the National Institutes of Health.
SOURCE USA TODAY Network reporting and research; Associated Press; Korey Stringer Institute at the University of Connecticut