Emergency Medical Technician (EMT) Trauma Practice Test

When a chest impact during sports leads to sudden collapse with no pulse, the scenario points to commotio cordis. This is a sudden cardiac arrest caused by a blunt impact to the chest that disrupts the heart’s electrical system, typically triggering ventricular fibrillation at a vulnerable moment in repolarization. The energy from the impact, especially in young athletes with a more compliant chest wall, can transiently interrupt the heart’s rhythm leading to immediate loss of effective circulation. This is different from aortic dissection, which usually presents with severe, tearing chest or back pain and occurs in people with vascular risk factors rather than from an isolated chest hit. Pneumothorax can cause breathing difficulties and unequal chest movement, and may progress to tension physiology, but the hallmark is respiratory findings rather than an immediate collapse from a rhythm disturbance. Rib fracture causes localized pain and potential injury to underlying structures, but it does not typically produce sudden cardiac arrest from a single chest blow. In this context, the key concept is that an impact to the chest can acutely trigger a dangerous heart rhythm, leading to immediate loss of pulse. The critical response is to start CPR right away and apply an AED as soon as it’s available, since defibrillation is essential to restore a normal rhythm in commotio cordis.