Hello! Thank you for asking on HCM! Regarding your question, I would explain that the right coronary lesion seems to be not a simple stenosis, but instead a complex one (it is a long stenotic artery, that needs to be treated as is considered clinically significant). As complex coronary lesions sometimes are a bit difficult to manage technically by stent implantation; it is at an utmost importance to make the right decision by direct on-site judgement of interventionist team, facing their personal experience and feasible environment. in your mom's case, it may be resolved by a long drug eluting stent or by utilizing more stents.
Hope to have been helpful to you. Greetings! Dr. Iliri