Objectives
Bicuspid aortic valve (BAV), characterized by valve malformation and risk for aortopathy, displays profound alteration in systolic aortic outflow and wall shear stress (WSS) distribution. The present study performed 4-dimenstional flow MRI in BAV patients with right-left (R-L) cusp fusion, focusing on the impact of valve function upon hemodynamic status within ascending aorta.
Methods
Four-dimensional flow MRI was performed in 50 R-L BAV subjects and 15 age- and aortic size-matched controls with tricuspid aortic valve. BAV patients were categorized into 3 groups according to their aortic valve function as follows: BAV with no more than mild aortic valve dysfunction (BAV-CTL, n=20), BAV with severe aortic insufficiency (BAV-AI, n=15), and BAV with severe aortic stenosis (BAV-AS, n=15).
Results
All R-L BAV patients exhibited peak WSS at the right-anterior position of the ascending aorta (BAV vs. TAV at right-anterior position: 0.91±0.23 N/m2 vs. 0.43±0.12 N/m2, p<0.001) with no distinct alteration between BAV-AI and BAV-AS. The predominance of dilatation involving the tubular ascending aorta (82%, type 2 aortopathy) persisted, with or without valve dysfunction. Compared to BAV-CTL subjects, the BAV-AI group displayed universally elevated WSS (0.75±0.12 N/m2 vs. 0.57±0.09 N/m2, p<0.01) in the ascending aorta, which was associated with elevated cardiac stroke volume (p<0.05). The BAV-AS group showed elevated flow eccentricity in the form of significantly increased standard deviation of circumferential WSS, which correlated with markedly increased peak aortic valve velocity (p<0.01).
Conclusions
The location of peak aortic WSS and type of aortopathy remained homogeneous among R-L BAV patients irrespective of valve dysfunction. Severe aortic insufficiency or stenosis resulted in further elevated aortic WSS and exaggerated flow eccentricity.