A 68-year-old woman develops acute pulmonary edema 4 days after an inferior myocardial infarction. Auscultation reveals a new harsh holosystolic murmur at the apex radiating to the axilla. She dies despite resuscitation. Autopsy shows a normally functioning left ventricle with a torn structure in its posterior region. Which structure most likely ruptured?
- A Posteromedial papillary muscle ✓
- B Anterolateral papillary muscle
- C Interventricular septum
- D Left ventricular free wall
Explanation
Papillary muscle rupture occurs 2 to 7 days after infarction when neutrophilic enzymatic digestion weakens the necrotic muscle. The posteromedial papillary muscle is supplied only by the posterior descending branch, usually from the right coronary artery, so it ruptures far more often than the anterolateral muscle, which has dual supply from the LAD and circumflex. Inferior infarcts therefore classically produce posteromedial papillary rupture with acute mitral regurgitation. A septal tear gives a left-to-right shunt with a parasternal murmur rather than apical radiation.
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.