Four days after an inferior STEMI managed conservatively, a 68-year-old man suddenly develops severe dyspnea and pulmonary edema. A harsh holosystolic murmur is heard at the apex radiating to the axilla, but there is no palpable thrill. Transthoracic echocardiography shows a flail posterior mitral leaflet with severe mitral regurgitation. What is the most likely mechanism?
- A Acute left ventricular free wall rupture
- B Rupture of the interventricular septum
- C Rupture of the posteromedial papillary muscle ✓
- D Rupture of an atherosclerotic plaque in the left main coronary artery
Correct answer: C. Rupture of the posteromedial papillary muscle
Explanation
Papillary muscle rupture occurs 2 to 7 days after MI and causes acute severe mitral regurgitation with flash pulmonary edema. The posteromedial papillary muscle is affected far more often because it has a single blood supply from the posterior descending artery, whereas the anterolateral muscle has dual supply. The absence of a thrill distinguishes it from septal rupture, and free wall rupture presents with tamponade rather than a murmur.
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.