Introduction: Bicuspid aortic valve (BAV) is known to alter ascending aorta (AAo) flow pattern and wall shear stress (WSS), and to develop aorta wall degeneration and aortopathy. A rare phenotype of BAV is a type 2 BAV or a functionally unicuspid aortic valve (UAV), in which more than two cusps are fused. The impacts of this rare form of BAV with a more constrained valve orifice area on aortic hemodynamics and WSS as well as potential risk for progressive aortic dilation are poorly understood. Thus, we evaluated the impact of different UAV phenotypes on aortic 3D hemodynamics compared to patients with type 1 BAV.
Hypothesis: Hemodynamic markers of aortic remodeling in UAV are more severe than in BAV and are affected by the UAV valve fusion patterns.
Methods: An IRB approved study identified 32 UAV patients (6F, 45.9±11.8Y, dAAo= 41.0±3.8mm). As a control group, 32 right-left (RL) fusion BAV patients matched for aortic diameter and age were included (7F, 49.2±11.9Y, dAAo= 41.1±3.7mm). Patients underwent cardiothoracic MRI including 4D flow MRI. The UAV cohort was divided into four subgroups according to valve morphology. Regional peak systolic velocities in three ROIs and systolic mean and peak WSS (top 2%) in six ROIs were calculated (Fig 1a).
Results: Fig 1a shows the systolic velocity MIP and regions of elevated WSS (marked red) compared to a normal WSS atlas based on a large healthy cohort. As shown, WSS was abnormally high in the AAo for all cases. In comparison with the BAV cohort, peak WSS was increased significantly (Fig 1b, marked fields, p<0.004). In addition, peak velocity was increased significantly in AAo for all of the four subgroups of UAV compared to the BAV cohort (p<0.002).
Conclusions: Depending on UAV morphology, significantly increased WSS and peak velocities were observed in UAV compared to BAV patients in various regions of the aorta. The results support our hypothesis that the markers of UAV are impacted by valve fusion pattern and can be more severe than in BAV patients.