Accidental hypothermia — ABEM Board MCQ

Correct answer: C — Cardiac tamponade

The most likely diagnosis is cardiac tamponade. This patient has obstructive shock physiology: sudden severe chest pain, dyspnea, syncope, hypotension, and tachycardia. The decisive finding is bedside ultrasound showing a pericardial effusion with right atrial collapse, which indicates tamponade physiology from elevated intrapericardial pressure impairing cardiac filling and reducing cardiac output. Pulmonary edema would cause hypoxemia/crackles and usually lung B-lines rather than pericardial effusion with chamber collapse. Aortic stenosis can cause syncope and chest pain but would not acutely produce pericardial effusion with right atrial collapse. Pericarditis without shock may cause chest pain and effusion but does not explain hypotension and right-sided chamber collapse. Tension pneumothorax causes obstructive shock but would be suggested by unilateral absent breath sounds, pleural air/lung sliding abnormalities, and mediastinal shift rather than pericardial effusion.

Reference: American College of Cardiology. 2025 Concise Clinical Guidance: An ACC Expert Consensus Statement on the Diagnosis and Management of Pericarditis. J Am Coll Cardiol. 2025. https://www.jacc.org/doi/10.1016/j.jacc.2025.05.023