Commotio cordis (Latin, "agitation or disruption of the heart") is a rare disruption of heart rhythm that occurs as a result of a blow to the area directly over the heart (the precordial region) at a critical instant during the cycle of a heartbeat, 97% fatal if not treated within three minutes. This sudden rise in intracavitary pressure leads to disruption of normal heart electrical activity, followed instantly by ventricular fibrillation, complete disorganization of the heart's pumping function, and cardiac arrest. It is not caused by mechanical damage to the heart muscle or surrounding organs and is not the result of heart disease. Its incidence in the United States is fewer than 20 cases per year, often occurring in boys participating in sports, most commonly in baseball when a ball strikes a player in the chest. Commotio cordis can occur only upon impact within a narrow window of about 40 milliseconds in the cardiac electrical cycle, explaining why it is so rare. If cardiopulmonary resuscitation (CPR) combined with use of an on-site automated external defibrillator is employed within three minutes of the impact, survival from commotio cordis can be as high as 58 percent. Assessment There are only 1020 cases annually in the United States. These cases occur mostly in boys and young men (mean age 15), usually during sports participation. It occurs most frequently in baseball when the hard ball strikes an unprotected chest, although there have been cases of commotio cordis in players using a chest protector. It is usually caused by a projectile, but can also be caused by a blow from another player's elbow or other body part. Being less developed, the thorax of an adolescent is likely more prone to this injury than a mature adult. Over a period of assessment from 20062012, the survival rate was 58 percent, which was an improvement over the years 19932006 when only 34 percent of victims survived. This increase is likely due to prompt CPR, access to defibrillation, and higher public awareness of this phenomenon. Potential for sudden death Due to ventricular fibrillation and resultant cessation of the cardiac output to vital organs, commotio cordis has a high fatality rate, indicated by two studies to be 7275 percent, with survival decreasing substantially if effective resuscitation was not performed within three minutes of the impact event. In a United States timeline analysis, survival was only ten percent over the