Tierney ESS, et al. - In view of no observed treatment differences in the rates of aortic-root growth or clinical outcomes with atenolol versus losartan in the Marfan syndrome from the Pediatric Heart Network randomized trial, the treatment effects on aortic stiffness were reported and the baseline aortic stiffness predictability of aortic-root growth and clinical outcomes in patients with the Marfan syndrome were determined. Atenolol was associated with a decline in the aortic-root stiffness index (SI), unlike losartan. Higher baseline aortic-root SI and elastic modulus were observed to be correlated with a smaller decrease in aortic-root z-score and increased risk for clinical outcomes. The data suggest that non-invasive aortic stiffness measures facilitate recognition of patients at higher risk for progressive aortic enlargement and adverse clinical outcomes, potentially allowing for closer monitoring and more aggressive therapy.