A 58-year-old woman develops acute pulmonary edema and a new holosystolic murmur at the apex on day 3 after an acute inferolateral STEMI. Echocardiography confirms severe mitral regurgitation with a flail posterior leaflet. Which structure has most likely ruptured?
- A Interventricular septum
- B Left ventricular free wall
- C Posterior papillary muscle ✓
- D Chordae tendineae of the anterior leaflet
Correct answer: C. Posterior papillary muscle
Explanation
Papillary muscle rupture is a mechanical complication of acute MI, typically occurring 2-7 days post-infarction, causing acute severe mitral regurgitation. The posterior papillary muscle is supplied by a single coronary territory (right or left circumflex artery) and is more vulnerable than the anterior papillary muscle. Free wall rupture causes tamponade, not a murmur. Septal rupture causes a left-to-right shunt. Robbins 10th ed, Chapter 12.
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.