Bicuspid Aortic Valve Is Associated With Altered Wall Shear Stress in the Ascending Aorta

Background-Hemodynamics may play a role contributing to the progression of bicuspid aortic valve (BAV) aortopathy. This study measured the impact of BAV on the distribution of regional aortic wall shear stress (WSS) compared with control cohorts. Methods and Results-Local WSS distribution was measured in the thoracic aorta of 60 subjects using 4-dimensional (4D) flow-sensitive magnetic resonance imaging. WSS analysis included 15 BAV patients: 12 with fusion of the right-left coronary cusp (6 stenotic) and 3 with fusion of the right and noncoronary cusp. The right-left BAV cohort was compared with healthy subjects (n=15), age-appropriate subjects (n=15), and age-/aorta size-controlled subjects (n=15). Compared with the age-appropriate and age-/aorta size-matched controls, WSS patterns in the right-left BAV ascending aorta were significantly elevated, independent of stenosis severity (peak WSS=0.9 +/- 0.3 N/m(2) compared with 0.4 +/- 0.3 N/m(2) in age-/aorta size-controlled subjects; P<0.001). Time-resolved (cine) 2D images of the bicuspid valves were coregistered with 4D flow data, directly linking cusp fusion pattern to a distinct ascending aortic flow jet pattern. The observation of right-anterior ascending aorta wall/jet impingement in right-left BAV patients corresponded to regions with statistically elevated WSS. Alternative jetting patterns were observed in the right and noncoronary cusp fusion patients. Conclusions-The results of this study demonstrate that bicuspid valves induced significantly altered ascending aorta hemodynamics compared with age-and size-matched controls with tricuspid valves. Specifically, the expression of increased and asymmetric WSS at the aorta wall was related to ascending aortic flow jet patterns, which were influenced by the BAV fusion pattern. (Circ Cardiovasc Imaging. 2012;5:457-466.)