A 64-year-old man develops acute pulmonary edema and a new pansystolic murmur 4 days after an inferior myocardial infarction. Echocardiography shows severe mitral regurgitation with a flail leaflet. Which structure has most likely ruptured?

• A Anterolateral papillary muscle
• B Posteromedial papillary muscle ✓
• C Interventricular septum
• D Anterior leaflet chordae tendineae only

Explanation

Papillary muscle rupture occurs 2 to 7 days after infarction and produces catastrophic mitral regurgitation. The posteromedial papillary muscle is supplied solely by the posterior descending artery, whereas the anterolateral papillary muscle has dual supply from both circumflex and left anterior descending branches. This single-vessel supply makes the posteromedial muscle far more vulnerable, especially in inferior infarction. Septal rupture gives a left-to-right shunt rather than pure mitral regurgitation.

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.