Talk on twitter going around about it possibly being Commotio Cordis.
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Commotio cordis (Latin, "agitation of the heart") is an often lethal 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 time during the cycle of a heart beat, producing what is termed an R-on-T phenomenon that leads to the condition. It is a form of ventricular fibrillation (V-Fib), not mechanical damage to the heart muscle or surrounding organs, and not the result of heart disease. The survival rate is 58%, which is an increase in comparison to years 1993–2012, where only 34% victims survived. This increase is likely caused by the prompt CPR, access to defibrillation and higher public awareness of this condition.[1]
Commotio cordis occurs mostly in boys and young men (average age 15), usually during sports, most frequently baseball, often despite a chest protector. It is usually caused by a projectile, but can also be caused by the blow of an elbow or other body part. Being less developed, the thorax of an adolescent is likely more prone to this injury given the circumstances.
Commotio cordis is a very rare event, but nonetheless is often considered when an athlete presents with sudden cardiac death. Some of the sports which have a risk for this cause of trauma are baseball, American football, association football, ice hockey, polo, rugby football, cricket, softball, pelota, fencing, lacrosse, boxing, professional wrestling, hurling and martial arts (see Touch of Death). Children are especially vulnerable, possibly due to the mechanical properties of their thoracic skeleton.[3] From 1996 to spring 2007, the USA National Commotio Cordis Registry had 188 cases recorded, with about half occurring during organized sports.[4] Almost all (96%) of the victims were male, the mean age of the victims during that period was 14.7 years, and fewer than one in five survived the incident.[4]