The posteromedial papillary muscle is the most likely to rupture during an acute myocardial infarction causing severe acute mitral valve regurgitation which can be life threatening if not immediately surgically repaired.

There are two papillary muscles that comprise part of the complex anatomy of the mitral valve. The anterolateral papillary muscle receives dual blood supply from the left anterior descending coronary artery and the left circumflex coronary artery in most individuals while the posteromedial papillary muscle receives its sole blood supply from the right coronary artery. Complete infarction of the posteromedial papillary muscle can occur during an inferior MI (from thrombosis of the right coronary artery) while only partial or no damage will be done to the anterolateral papillary muscle during an anterior (left anterior descending) or lateral (circumflex) infarction since there is dual blood supply to this papillary muscle. Thus, the posteromedial papillary muscle is the most likely to rupture.