Age-Related Changes of Shape and Flow Dynamics in Healthy Adult Aortas: A 4D Flow MRI Study

BACKGROUND Abnormal flow dynamics play an early and causative role in pathologic changes of the ascending aorta. PURPOSE To identify: 1) the changes in flow, shape, and size that occur in the ascending aorta with normal human ageing and 2) the influence of these factors on aortic flow dynamics. STUDY TYPE Retrospective. SUBJECTS In all, 247 subjects (age range 19-86 years, mean 49 ± 17.7, 169 males) free of aortic or aortic valve pathology were included in this study. Subjects were stratified by youngest (18-33 years; n = 64), highest (>60 years, n = 67), and the middle two quartiles (34-60 years, n = 116). FIELD STRENGTH/SEQUENCE Subjects underwent a cardiac MRI (3T) exam including 4D-flow MRI of the aorta. ASSESSMENT Aortic curvature, arch shape, ascending aortic angle, ascending aortic diameter, and the stroke volume normalized by the aortic volume (nSV) were measured. Velocity, vorticity, and helicity were quantified across the thoracic aorta. STATISTICAL TESTS Univariate and multivariate regressions were used to quantify continuous relationships between variables. RESULTS Aortic diameter, ascending aortic angle, shape, and curvature all increased across age while nSV decreased (all P  10 times that of diameter and other shape factors. DATA CONCLUSION Aortic shape influences flow dynamics in younger subjects. Flow conditions become increasingly disturbed with advancing age, and in these conditions nSV has a more dominant effect on flow patterns than shape factors. LEVEL OF EVIDENCE 3 Technical Efficacy: Stage 1 Stage 1 J. Magn. Reson. Imaging 2018.