Background The aorta in patients with bicuspid aortic valve (BAV) is larger and grows more rapidly than in patients with tricommissural aortic valve. Young patients with BAV can have significant aortic dilation that places them at risk for morbidity and mortality.

Objective The aims of this study were to determine the rate of growth of the aorta in young patients with BAV and to identify predictors of significant dilation and rapid aortic growth.

Methods 333 patients were randomly selected from an inception cohort of 1192 patients with BAV identified between 1986 and 1999.

Results Median age at the most recent study was 13.5 (0–30) years, 74% were male. Moderate/severe (Z>4) aortic root and ascending aortic dilation was present in 14/333 (5%) and 53/333 (16%) of patients, respectively. In longitudinal follow-up, only a minimal change in aortic Z-score was noted. Predictors of moderate/severe aortic root dilation included moderate/severe aortic regurgitation, absence of moderate/severe aortic stenosis and fusion of the right and left coronary leaflets. Predictors of moderate/severe ascending aortic dilation included moderate/severe aortic regurgitation and absence of aortic coarctation.

Conclusion Moderate/severe dilation of the ascending aorta is common in young patients with BAV, but moderate/severe dilation of the aortic root is less common. The Z-scores for both remained relatively constant over time even in patients with significant dilation, implying that young children with moderate/severe aortic dilation may be at the highest risk for dilation-related complications as adults.