The most common MI responsible for chordae rupture is MI of which coronary artery?

• A. RCA
• B. LAD
• C. Left Circumflex
• D. Posterior Descending Artery

Answer: (B)

Rupture of the papillary muscle causing acute mitral regurgitation after a heart attack most often involves the posteromedial papillary muscle. That muscle is supplied by a single artery, the posterior descending artery. When this artery is infarcted, the posteromedial papillary muscle is at high risk of rupture, leading to sudden mitral regurgitation. In contrast, the anterolateral papillary muscle has dual blood supply from the LAD and left circumflex, making rupture less likely. So the artery most commonly implicated is the posterior descending artery (often arising from the RCA in most people).