Serial magnetic resonance or computed tomography angiography studies were retrospectively reviewed in 25 patients evaluated with 4D Flow. All studies were performed for clinical indications. Thirteen patients had BAV (26.5 years of age, 5 female, 3.5 ± 0.7 cm baseline aortic size), and 12 with tricuspid aortic valve (TAV) served as controls (30.7 years of age, 3 female, 3.4 ± 0.5 cm baseline aortic size). The patients with BAV were relatively free of significant aortic valve disease; only 3 had greater than mild stenosis and 1 greater than mild insufficiency. None of the patients with TAV had valve disease. Ascending aortic diameters were measured at standard levels by 2 blinded reviewers, and the growth rate of the maximally enlarged segment was determined. Using a previously described qualitative approach, ascending aortic blood flow was graded as normal or mildly or markedly eccentric (2). All TAV controls had normal flow, whereas 10 of the 13 patients with BAV had abnormal flow (7 markedly eccentric). Normalized flow displacement from the vessel center, a recently developed parameter to quantify flow eccentricity, was calculated as well (4). Growth rates for controls and patients with BAV, and within the BAV group based on the degree of eccentric flow, were compared with unpaired Student t tests. Growth rates were also correlated with the flow displacement variable using a linear regression model.