Background Bicuspid aortic valve (BAV) is often associated with a concomitant aortopathy. However, few studies have evaluated the effect of the aortic valve (AV) phenotype on the rate of dilation of the aorta. This study aimed to compare the progression rate of aorta dimensions according to AV phenotype (BAV vs tricuspid AV (TAV)), fusion type and sex in patients with aortic stenosis (AS).Methods 310 patients with AS (224 TAV and 86 BAV) recruited in the Metabolic Determinants of the Progression of Aortic Stenosis study (PROGRESSA, NCT01679431) were included in this analysis. Doppler echocardiography was performed annually to assess AS severity and measure ascending aorta (AA) dimensions. Baseline and last follow-up visit measurements were used to assess the annualised change.Results Median AA annualised change was larger in BAV versus TAV (0.33±0.65 mm/year vs 0.21±0.56 mm/year, p=0.04). In the whole cohort, BAV phenotype and higher low-density lipoprotein (LDL) levels were significantly associated with fast progression of AA dilation in univariate analysis (OR 1.80, 95% CI 1.08 to 2.98, p=0.02; 1.37, 95% CI 1.04 to 1.80, p=0.03, respectively). AA dilation rate did not vary according to the BAV subtype (p=0.142). Predictors of AA progression rate were different between valve phenotypes, with higher apolipoprotein B/apolipoprotein A-I ratio, higher baseline peak aortic jet velocity (Vpeak) and smaller baseline AA diameter in the TAV cohort (all p<0.05) versus absence of hypertension, higher LDL levels and smaller baseline AA diameter in the BAV cohort (all p<0.02). In men, higher baseline Vpeak and smaller baseline AA (p<0.001) were independently associated with increased annualised AA dilation, while in women, higher LDL levels (p=0.026) were independently associated with faster AA dilation.Conclusion This study suggests that BAV is associated with faster dilation of the AA. Predictors of AA dilation are different between valve phenotype and sex, with higher LDL levels being associated with faster AA dilation in BAV.