Four days after an inferior STEMI, a 58-year-old man suddenly develops pulmonary edema with a new holosystolic murmur at the apex radiating to the axilla. Echocardiography shows severe mitral regurgitation with a flail leaflet but no ventricular septal defect. The most likely mechanism is:
- A Acute rheumatic valvulitis of the mitral valve
- B Free wall rupture with tamponade
- C Rupture of the posteromedial papillary muscle ✓
- D Infective endocarditis with leaflet perforation
Correct answer: C. Rupture of the posteromedial papillary muscle
Explanation
Papillary muscle rupture occurs 2 to 7 days after myocardial infarction and classically follows inferior infarction because the posteromedial papillary muscle has a single blood supply from the posterior descending artery, whereas the anterolateral papillary muscle has dual supply. Rupture produces flail leaflet and catastrophic acute mitral regurgitation. Free wall rupture presents with tamponade rather than a regurgitant murmur, and the remaining options lack the temporal and ischemic context.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.