|Human adult thorax, showing the outline of the heart (in red). The sensitive zone for mechanical induction of heart rhythm disturbances lies between the 2nd and the 4th ribs, to the left of the sternum|
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.
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.