The Effect of Losartan in Bicuspid Aortic Valve Patients

Inclusion Criteria: * Adults \>age 18 years and \< 65 years old * Able to give informed consent * Presence of a bicuspid aortic valve (functional or true bicommisural)and ascending aorta or sinus of Valsalva \>4.0cm * No contraindications to treatment with Losartan, an Angiotensin II receptor blocker * Able to safely participate in a 4 week drug washout period if currently taking an angiotensin II receptor blocker or ACE inhibitor. Exclusion Criteria: * Unable to safely take losartan due to one or more of the following: * Hypersensitivity to losartan or other angiotensin receptor blockers * Pregnancy * Nursing mothers * History of angioedema * Hypotension - chronically volume depleted patients * Hepatic or renal impairment (Cr\>1.5mg/dL) * Hyperkalemia (K+\>4.8) * Renal artery stenosis * Severe congestive heart failure (class III-IV) * Currently taking potassium supplements or salt substitutes containing potassium * Currently taking lithium * Prior surgical intervention to aorta or aortic valve * Unable or unwilling to give informed consent and follow up with study activities * Currently taking an angiotensin receptor blocker or ACE inhibitor specifically for hypertension and are therefore unable to or are unwilling to participate in a 4 week drug washout period. * Females of child bearing who are unwilling to practice adequate birth control throughout the study.