Bicuspid aortic valve (BAV) is associated with abnormal valve-mediated hemodynamics including high velocity jets and elevated wall shear stress (WSS). This study investigated interval changes in flow and WSS in a multi-year follow-up study. This cross-sectional study included n = 44 patients with BAV (age = 44.9 ± 12 years), n = 17 patients with tricuspid aortic valve and thoracic aortic dilatation (TAV with dilation, age = 54.6 ± 16.5 years), and n = 9 healthy controls (age = 49.3 ± 14.7 years) underwent baseline and serial aortic 4D flow MRI (follow-up duration: BAV: 2.6 ± 0.7 years, TAV with dilation: 2.7 ± 0.5 years, controls: 1.1 ± 0.5 years). Data analysis included quantification of aortic dimensions, peak systolic velocities, as well as regional 3D WSS in the ascending aorta. At baseline, BAV patients demonstrated uniformly elevated peak velocity and WSS compared to TAV with dilation and control groups (peak velocity 2.2 m/s vs. 1.6 m/s vs. 1.5 m/s, p < 0.004; WSS: 0.74 Pa vs. 0.45 Pa vs. 0.55 Pa, p < 0.001). For BAV, peak velocity increased from baseline to follow up (2.2 ± 0.8 to 2.3 ± 0.9 m/s, p < 0.001) while WSS decreased (0.74 ± 0.22 to 0.65 ± 0.21 Pa, p < 0.001). Aortic growth was minimal for both BAV (0.05 cm/year) and TAV with dilation (0.03-0.04 cm/year) patients. For BAV patients, increase of ascending aorta peak velocities indicated worsening of valve function at follow-up. Compared to TAV with dilation patients, BAV patients demonstrated a reduction in WSS which may indicate a compensatory mechanism to reduce elevated WSS forces by aortic remodeling.
Keywords: 4D flow MRI; Aortic disease; Bicuspid aortic valve; Flow imaging; Follow-up study.