Therefore, the objective of the proposed research is to use this methodology to compare aortic vascular function in individuals with MFS under conventional treatment using a beta blocker (Atenolol) or an angiotensin receptor blocker (Losartan). We propose a randomized, prospective, double-blinded superiority study to compare the actions of Losartan with Atenolol on vascular function in a group of 30 patients with MFS. Our research group has the unique capability to perform an analysis of the vascular effects of these therapies.