A 56-year-old man is unresponsive and pulseless after a motor vehicle collision with no obvious injuries. What is the most likely cause?

• A. Seizure disorder
• B. Acute coronary syndrome
• C. Trauma
• D. Suicide

Answer: (B)

The key idea is that sudden cardiac arrest in an adult after a crash is most often due to a cardiac event, not the trauma itself. Acute coronary syndrome occurs when a coronary artery is blocked or severely narrowed, leading to myocardial ischemia. That ischemia can trigger a deadly rhythm, such as ventricular fibrillation, and cause immediate loss of a pulse. In a 56-year-old, this is a common and plausible cause, especially when there are no obvious external injuries to explain the collapse.

Seizure activity can produce unresponsiveness, but it doesn’t typically present as abrupt pulseless collapse in this scenario without a history of seizures or convulsive activity. Trauma could cause arrest if there were major injuries or bleeding, but the description notes no obvious injuries, making a traumatic cause less likely. Suicide isn’t indicated by the information given and is less consistent with the presentation.