What is a key risk factor for the rupture of the posterior papillary muscle during an inferior wall MI?

The rupture of the posterior papillary muscle during an inferior wall myocardial infarction (MI) is closely associated with its blood supply. The posterior papillary muscle typically receives blood from the right coronary artery (RCA) in most individuals, thereby depending on a single blood supply.

When there is an inferior wall MI, especially due to occlusion of the RCA, the blood flow to the areas supplied by this artery, including the posterior papillary muscle, can be significantly compromised. This lack of adequate blood flow can lead to ischemia of the muscle, weakening it and ultimately increasing the risk of rupture.

In contrast, some heart muscles, like the anterior papillary muscle, might have a dual blood supply from the left anterior descending (LAD) and circumflex arteries, which provides a buffer against ischemia. However, the dependence of the posterior papillary muscle on a singular source makes it particularly vulnerable during events that disrupt this supply, such as an inferior wall MI. Thus, the single blood supply is a critical factor in its risk of rupture.