A 65-year-old man on day 5 after a large anterior STEMI suddenly loses consciousness. He is pulseless with electrical activity on the monitor but no palpable pulse. Echocardiography shows a moderate pericardial effusion. What is the most likely diagnosis?
- A Ventricular septal rupture
- B Left ventricular free wall rupture ✓
- C Papillary muscle rupture
- D Pulmonary embolism
Correct answer: B. Left ventricular free wall rupture
Explanation
Left ventricular free wall rupture typically occurs 3 to 7 days post-MI when necrosis is maximal. It presents with sudden hemodynamic collapse and electromechanical dissociation (pulseless electrical activity). Pericardial effusion with tamponade is the hallmark. VSD produces a harsh pansystolic murmur with a thrill. Papillary muscle rupture causes acute pulmonary edema and a new pansystolic murmur at the apex. PE would not cause pericardial effusion.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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