What is Commotio Cordis? Commotio Cordis is a syndrome that results from a blunt impact to the chest which leads to cardiac arrest. It is a poorly recognized and underreported event that happens to healthy young athletes as a result of a low-energy, non-penetrating blow to the chest. Commotio Cordis does not result solely from the force of a blow. It is largely the result of the exquisite timing of the blow during a narrow window within the repolarization phase of the cardiac cycle, 15 to 30 msec prior to the peak of the Twave. Young athletes are especially at risk because of the pliability of their chest walls. Athletes wearing chest protectors have died while playing baseball, lacrosse, hockey and softball. 75 cases have been well documented since the formation of the United States Commotio Cordis Registry (Minneapolis, MN) three years ago. The true number of deaths is unknown because of underreporting and misclassification. Resuscitation of the victims of commotio cordis is seldom successful. Time is a critical factor after the onset of the event. Early cardiopulmonary resuscitation and especially early defibrillation is essential. In animal studies all victims that were defibrillated within 2 minutes survived. To prevent deaths from Commotio Cordis it is necessary to train coaches, bystanders and other sports personnel in the recognition of this event and the timely response. Basic life support training and access to automatic external defibrillators (AED's) are crucial to achieve this goal.