A 58-year-old man with acute anterior wall myocardial infarction is admitted to the ICU. On day 5 post-MI, he suddenly develops acute dyspnea, hypotension, and a new harsh holosystolic murmur best heard at the apex. Echocardiography shows acute severe mitral regurgitation with normal left ventricular systolic function. The pathological process marked **C** in the healing timeline diagram is responsible for the structural weakness that predisposes to this complication. Which of the following best explains why the posteromedial papillary muscle is more vulnerable to rupture than the anterolateral papillary muscle in this clinical scenario?