Commotio cordis (Latin for "agitation of the heart") is a rare cause of sudden cardiac arrest triggered by a blunt, non-penetrating impact to the chest during a critically vulnerable window in the cardiac cycle. The impact itself does not cause structural damage to the heart or chest; it is the precise timing of the blow that triggers ventricular fibrillation.
How it happens
During each heartbeat, there is an extremely brief period (approximately 10 to 30 milliseconds, just before the peak of the T-wave on an ECG) when the heart is particularly susceptible to mechanical stimulation. If a blow to the chest occurs during this window, it can trigger ventricular fibrillation and cardiac arrest. Outside this window, the same blow would cause no dangerous arrhythmia.
Who is most at risk
Commotio cordis occurs most often in young males participating in sport, particularly those involving a hard projectile (baseball, cricket, ice hockey, lacrosse). The chest wall in children and young adults is more compliant (less rigid) than in older adults, which may allow more direct force transmission to the heart. It has also been reported in other settings, including impacts during play or physical altercations.
Survival
Commotio cordis is rapidly fatal without immediate treatment. Survival depends entirely on the speed of defibrillation. With immediate CPR and defibrillation (for example, from an on-site AED), survival rates have improved significantly, but remain lower than for other causes of VF. This is why the availability of AEDs at sports venues is critically important.
Prevention
Protective chest equipment (chest guards) is widely used in at-risk sports, though evidence on its effectiveness in preventing commotio cordis specifically is mixed. Awareness of the condition and immediate access to an AED remain the most important protective factors.
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