Distribution of blood flow velocity in the normal aorta: Effect of age and gender

Purpose: To apply flow distribution analysis in the entire aorta across a wide age range from pediatric to adult subjects. Material and Methods: In all, 98 healthy subjects (age 9–78 years, 41 women) underwent 4D flow MRI at 1.5T and 3T for the assessment of 3D blood flow in the thoracic aorta. Subjects were categorized into age groups: group 1 (n = 9, 5 women): 9–15 years; group 2 (n = 13, 8 women): 16–20 years; group 3 (n = 27, 14 women): 21–39 years; group 4 (n = 40, 11 women): 40–59 years; group 5 (n = 9, 3 women): >60 years. Data analysis included the 3D segmentation of the aorta, aortic valve peak velocity, mid-ascending aortic diameter, and calculation of flow velocity distribution descriptors (mean, median, standard deviation, incidence of velocities >1 m/s, skewness, and kurtosis of aortic velocity magnitude). Ascending aortic diameter was normalized by body surface area. Results: Age was significantly associated with normalized aortic diameter (R = 0.73, P < 0.001), skewness (R = 0.76, P < 0.001), and kurtosis (R = 0.74, P < 0.001), all adjusted by heart rate. Aortic peak velocity and velocity distribution descriptors, adjusted by heart rate, were significantly different between age groups (P < 0.001, analysis of covariance). Skewness and kurtosis significantly increased (P < 0.001) during adulthood (>40 years) as compared with childhood (<21 years). Men and women revealed significant differences (P ≤ 0.05) for peak velocity, incidence, mean, median, standard deviation, and skewness, all adjusted by heart rate. Conclusion: Aortic hemodynamics significantly change with age and gender, indicating the importance of age- and gender-matched control cohorts for the assessment of the impact of cardiovascular disease on aortic blood flow. Level of Evidence: 3. Technical Efficacy: Stage 5. J. Magn. Reson. Imaging 2018;47:487–498.