Phase-contrast MRI assessment of the thoracic aortic wall shear stress association with ascending aortic progression

Ascending aortic growth in BAV varies widely, and baseline diameter insufficiently predicts individual risk; we assessed whether abnormal regional WSS surface burden relates to later AAo enlargement during longitudinal follow-up.

The analysis included 37 patients with BAV and 66 healthy control subjects matched for age and sex. Baseline thoracic aortic phase-contrast/4D-flow MRI was acquired using a 3.0-T Siemens MAGNETOM Skyra scanner to evaluate flow-related parameters across the aortic root, AAo, arch, and proximal descending thoracic aorta. The velocity-encoded 3D acquisition was planned to include the thoracic aorta, and axial or oblique axial source images were used for anatomical lo calization and AAo diameter measurement. Imaging parameters included TR 38.88 ms, TE 68.8 ms, flip angle 8°, matrix 256 × 256, field of view 300 mm, spatial resolution 1.4 × 1.4 mm², slice thickness 3 mm, and interslice gap 0.6 mm. Patient WSS maps were evaluated against healthy-control 95 % confidence interval reference maps, and higher AAo growth was defined as annual enlargement greater than 0.25 mm/year.

During 6.2-year median follow-up, higher-growth patients showed greater elevated AAo WSS area (20.6 vs. 6.0 %; p=0.021).

Phase-contrast MRI-derived elevated WSS area may support individualized BAV surveillance.