Papillary Muscle Rupture

Papillary muscle rupture is a mechanical complication of acute myocardial infarction (MI). Ischemic necrosis weakens the papillary muscle, allowing part or all of it to tear; the mitral leaflet it normally anchors then becomes flail and fails to close during systole. The result is acute, severe mitral regurgitation (MR). The usual window is 2–7 days after infarction, often around days 3–5. The posteromedial papillary muscle ruptures much more often than the anterolateral muscle because it commonly receives a single blood supply from the posterior descending artery. In right-dominant circulation, that artery usually arises from the right coronary artery; in left-dominant circulation, it arises from the circumflex artery. The anterolateral muscle usually has collateral protection from both the left anterior descending and circumflex arteries. Reperfusion has made rupture uncommon, with reported incidence around 0.05%–0.26% of MI patients. It remains immediately life-threatening: reported in-hospital mortality ranges from 10% to 40%, and mortality with medical management alone may reach 75% within the first 24 hours. A patient with suspected PMR needs a cardiac surgical centre and a heart-team response, not routine post-MI observation.