Posteromedial muscle rupture is almost always the only papillary muscle of concern as one would need to disrupt the dual blood supply of the anterolateral papillary muscle for it to rupture.
https://www.ncbi.nlm.nih.gov/books/NBK499976/
Also, papillary muscle always causes at least some degree of MR, so I removed the word often because it is unnecessarily cautious. Whether the MR is significant is another matter. I would support saying "often causes significant mitral regurgitation" as an alternative.
Also, in the extra notes it says the "papillary muscle" is supplied by the RCA. This simply isn't true, firstly, there are two papillary muscles, and of those, one (the posteromedial) may be supplied by the RCA if circulation is right dominant. The anterolateral has dual blood supply from the LAD and LCx.
https://www.ncbi.nlm.nih.gov/books/NBK537357/
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