A patient develops a new pansystolic murmur at the apex 4 days after a large anterior STEMI. Echocardiography shows a flail posterior mitral leaflet with severe MR. This mechanical complication is most likely caused by:

• A Papillary muscle rupture of the anterolateral papillary muscle
• B Ventricular septal defect
• C Left ventricular free wall rupture
• D Papillary muscle rupture of the posteromedial papillary muscle ✓

Explanation

The posteromedial papillary muscle has a single blood supply (usually from the right coronary or posterior descending artery) and is thus more vulnerable to ischaemic rupture than the anterolateral papillary muscle, which has dual supply from LAD and LCx. Papillary muscle rupture typically presents 2–7 days post-MI with acute severe MR, pulmonary oedema, and cardiogenic shock. A VSD would show a harsh pansystolic murmur at the left sternal border with an oxygen step-up on right heart catheterisation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.