What type of injury causes ventricular fibrillation (VF) or ventricular tachycardia (VT) cardiac arrests?

Traumatic Injury Causing VF/VT Cardiac Arrests

Commotio cordis—a direct blow to the chest—is the primary traumatic injury that causes ventricular fibrillation or ventricular tachycardia leading to cardiac arrest. 1

Mechanism of Commotio Cordis

Commotio cordis occurs when blunt chest trauma delivers impact during the vulnerable period of the cardiac cycle (analogous to the R-on-T phenomenon), precipitating VF or pulseless VT. 1 This mechanism does not require structural cardiac damage—the electrical disruption alone triggers the lethal arrhythmia. 1

• The blow must occur during a critical 10-40 millisecond window of ventricular repolarization to trigger VF. 1
• Approximately 5-10 cases are reported nationwide annually across all age groups. 1
• This injury is most commonly seen in young athletes during sports activities involving projectiles (baseballs, hockey pucks, lacrosse balls). 1

Other Traumatic Mechanisms

Direct cardiac laceration from penetrating or severe blunt chest trauma can cause VF/VT, though this is far less common than commotio cordis. 2, 3

• Myocardial contusion with direct tissue injury may precipitate ventricular arrhythmias in rare cases. 2, 3
• VF in blunt trauma patients is uncommon and should prompt consideration of cardiac monitoring, as it may represent a salvageable rhythm if not caused by exsanguination or severe hypoxia. 3

Electrical Injury Mechanisms

Electric shock and lightning strikes cause VF/VT through direct electrical disruption of cardiac rhythm, representing a distinct category of injury-related cardiac arrest. 1

Electric Shock

• Alternating current (household/commercial) causes tetanic muscle contractions that "lock" the victim to the source, increasing exposure duration. 1
• Current flow through the heart during the vulnerable period (relative refractory period) precipitates VF, similar to unsynchronized cardioversion. 1

Lightning Strike

• Lightning acts as a massive instantaneous direct-current shock that simultaneously depolarizes the entire myocardium. 1
• The primary mechanism is VF or asystole, with cardiac arrest being the leading cause of death. 1
• Intrinsic cardiac automaticity may spontaneously restore rhythm after lightning strike, but concomitant respiratory arrest from thoracic muscle spasm often leads to secondary hypoxic cardiac arrest if ventilation is not supported. 1

Critical Clinical Distinctions

The vast majority of traumatic cardiac arrests do NOT present with shockable rhythms (VF/VT)—asystole and pulseless electrical activity predominate in trauma. 1 This makes commotio cordis and electrical injuries notable exceptions where defibrillation may be life-saving.

• In general trauma populations, VF/VT represents a small minority of arrest rhythms. 1
• When VF/VT does occur in trauma without obvious electrical injury or commotio cordis, consider direct myocardial injury or pre-existing cardiac disease as triggers. 2, 3
• Early ECG monitoring in blunt chest trauma can identify this small but salvageable subset of patients. 3

Resuscitation Priorities

Standard ACLS protocols apply to injury-related VF/VT, with attention to cervical spine precautions in trauma patients. 1

• Immediate defibrillation remains the definitive treatment for VF/VT regardless of mechanism. 1
• In lightning strike victims with multiple casualties, reverse triage applies—prioritize those in cardiac arrest, as they have excellent survival potential with immediate CPR and defibrillation. 1
• For electrical injuries with tissue destruction, aggressive fluid resuscitation is required post-ROSC to maintain diuresis and facilitate myoglobin excretion. 1