Contributing Factor of Proximal Arch Dilation in Patients with Bicuspid Aortic Valve-Wall Shear Stress or Upward Extension of Ascending Aorta Dilation?

Purpose: The dilation of proximal arch (PArc) was suspected to develop as a result of valve-related hemodynamics or in consequence to the upward extension of the ascending aorta (AAo) dilation. We aimed to investigate the one that could be the possible contributing factor in patients with bicuspid aortic valve (BAV). Methods: All enrolled BAV patients underwent four-dimensional flow magnetic resonance imaging. Contour-averaged circumferential wall shear stress (WSScirc,avg) and the diameter of the middle of AAo (mid-AAo) were compared between the patients with and without PArc dilation. Additionally, we analyzed the correlation between WSScirc,avg and aortic diameter at PArc section, as well as the correlation between the diameter of mid-AAo and that of PArc. Results: No significant difference was observed in WSScirc,avg at PArc section between the patients with and without PArc dilation (P=.621). However, the diameter of mid-AAo in the patients who suffered PArc dilation was higher than those without it (P=.007). In addition, the aortic diameter did not correlate with the WSScirc,avg at PArc level (R=-0.068, P=.701). The correlation was observed between PArc diameter and mid-AAo diameter (R=0.521, P=.002). Conclusion: Hemodynamics may not contribute to the development of PArc dilation. PArc diameter correlated with mid-AAo diameter, indicating PArc dilation may be secondary to the upward extension of AAo dilation. The influence of AAo dilation extending upward could be treated by AAo replacement; hence, a selective approach to transverse PArc replacement might be appropriate.