Papillary muscle rupture complicating acute myocardial infarction characteristically involves the posteromedial papillary muscle far more often than the anterolateral one. This predilection is best explained by which anatomical fact?

• A The posteromedial papillary muscle has a single blood supply from the posterior descending artery ✓
• B The posteromedial papillary muscle is subjected to higher wall stress during systole
• C The anterolateral papillary muscle is thicker and therefore less prone to ischemia
• D The posteromedial papillary muscle arises directly from the mitral annulus

Explanation

The anterolateral papillary muscle has a dual blood supply from the left anterior descending and circumflex arteries, so it is protected when either vessel occludes. The posteromedial papillary muscle depends solely on the posterior descending artery, so inferior or posterior infarction can devascularize it completely. Rupture causes acute severe mitral regurgitation, typically 2 to 7 days after infarction, presenting as pulmonary edema with a new apical systolic murmur.

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.