Magnetic resonance imaging 4-D flow-based analysis of aortic hemodynamics in Turner syndrome

Background: Cardiovascular surveillance is important in Turner syndrome because of the increased risk of aortic dilation and dissection with consecutively increased mortality. Objective: To compare 4-D flow MRI for the characterization of aortic 3-D flow patterns, dimensions and vessel wall parameters in pediatric patients with Turner syndrome and age-matched controls. Materials and methods: We performed 4-D flow MRI measuring in vivo 3-D blood flow with coverage of the thoracic aorta in 25 patients with Turner syndrome and in 16 female healthy controls (age mean ± standard deviation were 16 ± 5 years and 17 ± 4 years, respectively). Blood flow was visualized by time-resolved 3-D path lines. Visual grading of aortic flow in terms of helices and vortices was performed by two independent observers. Quantitative analysis included measurement of aortic diameters, quantification of peak systolic wall shear stress, pulsatility index and oscillatory shear index at eight defined sites. Results: Patients with Turner syndrome had significantly larger aortic diameters normalized to BSA, increased vortices in the ascending aorta and elevated helix flow in the ascending and descending aorta compared to controls (all P<0.03). Patients with abnormal helical or vortical flow in the ascending aorta had significantly larger diameters of the ascending aorta (P<0.03). Peak systolic wall shear stress, pulsatility index and oscillatory shear index were significantly lower in Turner patients compared to controls (p=0.02, p=0.002 and p=0.01 respectively). Conclusion: Four-dimensional flow MRI provides new insights into the altered aortic hemodynamics and wall shear stress that could have an impact on the development of aortic dissections.