A 35-year-old man presents with acute onset severe dyspnoea, hypotension (80/50 mmHg), and pulmonary oedema 5 days after an acute inferior wall myocardial infarction. On examination, there is a new loud holosystolic murmur at the cardiac apex radiating to the axilla. Echocardiography confirms acute severe mitral regurgitation. What is the most likely underlying mechanism?

• A Rupture of the chordae tendineae
• B Infective endocarditis of the mitral valve
• C Rupture of the posteromedial papillary muscle ✓
• D Rupture of the anterolateral papillary muscle

Explanation

The posteromedial papillary muscle is most commonly affected in papillary muscle rupture because it receives blood supply from a single coronary artery (usually the right coronary artery or left circumflex), unlike the anterolateral papillary muscle which has dual supply. Inferior wall MI involves the RCA territory, making posteromedial papillary muscle rupture the most likely cause of acute severe MR in this setting.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.