Although thought to be rare, sudden deaths caused by nonpenetrating chest wall 
impact in the absence of structural injury to the ribs, sternum, and heart 
(commotio cordis) are reported with increasing frequency. This phenomenon is 
described in individuals when they are struck by relatively innocent blows to 
the chest wall. Young male athletes aged 5 to 18 years are particularly at risk 
for this catastrophe. It has been described after blows to the chest from 
baseballs, softballs, hockey pucks, and other objects. Death is usually 
instantaneous, and successful resuscitation is uncommon. A recently reported 
experimental model provides clues to the mechanisms and inferences for the 
prevention and treatment of this devastating condition. This swine model shows 
that a) ventricular fibrillation results from low-energy chest wall impacts 
during a vulnerable period of repolarization, b) the risk of this event can be 
decreased with softer-than-standard baseballs, and c) prompt defibrillation is 
crucial for resuscitation to be successful.