Sorry but when you use the term "generally" in a medical context you can be sure the following statement is incorrect. This article is referring to the aortic root which cannot be stinted due to its proximity to the heart.
"Generally" refers to an average trend, not that all examples must follow that trend.
I am not that familiar with Marfan's or this case, so I don't know if this device is useful in this case (http://www.medtronic.com/patients/heart-valve-disease/about-...), but there are stent-grafts that also replace the aortic value so that the stent-graft can be used close to the heart, and you can be sure that medical device companies are looking at ways of using stent-grafts in close proximity to the aortic valve without requiring its replacement.
