Spanish to English Medical Medical: Health Care cardiology

I'm translating a cardiology report from Spanish (not sure what variety, but also not sure it matters) to American English. Under "Enfermedad actual" there is a line that says "estenosis segementaria [sic] severa de RO M de CX".

I'm tearing my hair out over these abbreviations. I've got "severe segmental stenosis of **RO M** of CX". I'm sure of the CX abbreviation (same in English & Spanish), but, as there are clearly some typos in the report in the first place, I can't even be sure it's not "ROM" instead of "RO M". I've searched every place I can think of, and can't come up with anything logical that fits here.

No doubt I will be submitting a few more requests for help, as this report is positively littered with abbr.'s, some only one letter long.