Commotio cordis is arrhythmia or sudden death from low-impact, blunt trauma to 
the chest without apparent heart injury. Ventricular fibrillation is the most 
common associated arrhythmia, and heart block, bundle branch block, and 
ST-segment elevation are also seen. Commotio cordis occurs most commonly in 
baseball but has also been reported in hockey, softball, and several other 
sports. Approximately two to four cases are reported each year, but the true 
incidence is uncertain. Survival is low, even when resuscitation is performed. 
Preventive measures include education of participants and coaches, chest 
protection, and softer baseballs. Other considerations include having external 
automatic defibrillators and trained personnel at youth sporting events.