A 58-year-old woman develops acute pulmonary edema and a new pansystolic murmur at the apex radiating to the axilla five days after an inferior myocardial infarction. Echocardiography shows a flail posterior mitral leaflet with normal left ventricular function. The most likely cause is:
- A Rupture of the posteromedial papillary muscle ✓
- B Free wall rupture with tamponade
- C Ventricular septal rupture
- D Acute rheumatic valvulitis
Correct answer: A. Rupture of the posteromedial papillary muscle
Explanation
Papillary muscle rupture occurs 2 to 7 days after infarction when coagulation necrosis weakens the muscle before granulation tissue strengthens it. The posteromedial papillary muscle is affected far more often because it has a single blood supply from the posterior descending artery. Septal rupture produces a harsh left parasternal murmur with a step-up in right ventricular oxygen saturation rather than a flail leaflet, excluding C.
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.