Commotio cordis occurs when a blunt blow to the chest during a specific moment in the heart’s electrical cycle results in sudden cardiac arrest.

“An impact at the right time in the electrical cardiac cycle can create an abnormal heart rhythm that could be life threatening,” she said.

“It has to be at a specific instant during that normal cardiac cycle where the electrical system is disrupted and then the heart goes into this abnormal electrical cycle,” Stauffer said ...

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.

Annually some 350,000 Americans go into cardiac arrest outside of a healthcare setting — and only an estimated 10% of them survive and fully recover.

"It happens within a critical period within the cardiac cycle. We're talking about 20 to 30 milliseconds within the cardiac cycle that the heart is vulnerable to this." Key Background ...

Although cardiac arrest is often confused with heart attacks, the two are quite different. Cardiac arrest is defined as the sudden loss of activity in the heart due to an irregular heartbeat while a ...